0001636282-26-000020 | 10-K | XBRL Viewer

[1]	Includes $10.5 million, $40.1 million and $48.5 million in related party expenses for the years ended December 31, 2025, 2024 and 2023, respectively.

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

Segment Reporting

12 Months Ended

Dec. 31, 2025

Segment Reporting [Abstract]

Segment Reporting

The Company operates under a single operating and reportable segment, which is the development of biopharmaceutical products for the treatment of patients with IBD and other immune-mediated diseases. The Company's Chief Operating Decision Maker ("CODM") is the Company's Chief Executive Officer. The Company's CODM uses consolidated Net loss as the measure of segment profit or loss and uses consolidated Total Assets as reported on the balance sheet as the measure of segment assets. The Company's CODM compares Net loss against budgeted and/or forecasted amounts to track the Company's financial performance against expectations and to inform, along with development timelines and scientific and commercial considerations, their decisions regarding resource allocations to fund the Company's development of its pipeline.

The following table sets forth the significant expenses provided to the CODM on a regular basis (in thousands):


	Year Ended December 31,
	2025		2024		2023
Revenue	$	—	$	—	$	886

Less:
Compensation	$	34,794	$	21,780	$	22,590
Stock-based compensation (1)	37,614		44,833		25,675
Research and development, excluding compensation and stock-based compensation (2) (3)	132,490		127,491		65,282
Other segment items (4) (5)	(49,695)		13,914		226,129
Segment net loss	$	155,203	$	208,018	$	338,790

Reconciliation of net loss
Adjustments and reconciling items	—		—		—
Consolidated net loss	$	155,203	$	208,018	$	338,790

(1)Includes $1.0 million, $15.6 million and $11.5 million in related party expenses for the years ended December 31, 2025, 2024 and 2023, respectively.

(2)Includes non-clinical study expenses, clinical trial expenses and manufacturing costs.

(3)Includes $10.5 million, $25.5 million and $37.1 million in related party expenses for the years ended December 31, 2025, 2024 and 2023, respectively.

(4)Includes general and administrative expenses such as audit, legal, and other professional fees, interest income, and Other expense, net. For the year ended December 31, 2025, includes a gain recognized in

connection with the sale of pegzilarginase to Immedica. For the year ended December 31, 2023, includes acquired IPR&D expense related to the Asset Acquisition, a gain on sale related to sale of Pegzilarginase to Immedica, and changes in the forward-contract liability related to the Asset Acquisition.

(5)Includes a $29.8 million decrease, a $20.4 million increase and a $18.9 million increase in fair value of CVR liability for the years ended December 31, 2025, 2024 and 2023, respectively.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

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+ Details

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2025

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets, liabilities, and equity and the amount of revenues and expenses. Actual results could differ significantly from those estimates. The most significant estimates and assumptions that management considers in the preparation of the Company's financial statements relate to accrued research and development costs; the valuation of consideration transferred in acquiring in-process research & development ("IPR&D"); the discount rate, probabilities of success, and timing of estimated cash flows in the valuation of the CVR liability; inputs used in the Black-Scholes model for stock-based compensation expense; estimated future cash flows used in calculating the impairment of right-of-use lease assets; and estimated cost to complete performance obligations related to revenue recognition. The consideration transferred in acquiring IPR&D in connection with the acquisition of Pre-Merger Spyre was comprised of shares of the Company’s common stock and shares of Series A Preferred Stock. To determine the fair value of the equity transferred, the Company considered the per share value of securities sold in the June 2023 PIPE, which was a financing event involving a group of accredited investors.

Cash and Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less from the date of purchase to be cash equivalents. Cash equivalents consist of money market funds and debt securities and are stated at fair value.

Marketable Securities

All investments have been classified as available-for-sale and are carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. Management determines the appropriate classification of its investments in debt securities at the time of purchase. The Company may hold securities with stated maturities greater than one year until maturity. All available-for-sale securities are considered available to support current operations and are classified as current assets. The Company presents credit losses as an allowance rather than as a reduction in the amortized cost of the available-for-sale securities.

For available-for-sale debt securities in an unrealized loss position, the Company first assesses whether it intends to sell, or it is more likely than not that it will be required to sell the security before recovery of its amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the security’s amortized cost basis is written down to fair value and recognized in other income (expense) in the results of operations. For available-for-sale debt securities that do not meet the aforementioned criteria, the Company evaluates whether the decline in fair value has resulted from credit losses or other factors. In making this assessment, management considers the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency, and adverse conditions specifically related to the security, among other factors. If this assessment indicates that a credit loss exists, an allowance is recorded for the difference between the present value of cash flows expected to be collected and the amortized cost basis of the security. Impairment losses attributable to credit loss factors are charged against the allowance when management believes an available-for-sale security is uncollectible or when either of the criteria regarding intent or requirement to sell is met.

Any unrealized losses from declines in fair value below the amortized cost basis as a result of non-credit loss factors is recognized as a component of accumulated other comprehensive (loss) income, along with unrealized gains. Realized gains and losses and declines in fair value, if any, on available-for-sale securities are included in other income (expense) in the results of operations. The cost of securities sold is based on the specific-identification method.

Restricted Cash

Restricted cash consisted of cash balances related to the Company's former operations in the United Kingdom for the period ended December 31, 2023. There were no restricted cash balances as of December 31, 2025 and 2024.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash, cash equivalents, marketable securities, and restricted cash. The Company’s investment policy limits investments to high credit quality securities issued by the U.S. government, U.S. government-sponsored agencies, highly rated banks, and corporate issuers, subject to certain concentration limits and restrictions on maturities. The financial instruments that potentially subject the Company to a concentration of credit risk consist principally of cash deposits. Accounts at each of the Company's two U.S. banking institutions are insured by the Federal Deposit Insurance Corporation (“FDIC”) up to $250,000 per depositor. As of December 31, 2025 and 2024, balances at the Company's U.S. banking institutions exceeded the FDIC limits. The Company has not experienced any losses on its deposits of cash, cash equivalents, and restricted cash and its accounts are monitored by management to mitigate risk. The Company is exposed to credit risk in the event of default by the financial institutions holding its cash, cash equivalents, and restricted cash, and bond issuers.

Property and Equipment

Property and equipment are stated at cost, net of accumulated depreciation and amortization. Depreciation and amortization are computed using the straight-line method over the estimated useful lives of the assets. Repairs and maintenance that do not extend the life or improve an asset are expensed as incurred. Upon retirement or sale, the cost of disposed assets and their related accumulated depreciation and amortization are removed from the balance sheet. Any gain or loss is credited or charged to operations.

The useful lives of the property and equipment are as follows:


Laboratory equipment			5 years
Furniture and office equipment			5 years
Computer equipment			3 years
Software			3 years
Leasehold improvements			Shorter of remaining lease term or estimated useful life

The Company did not have any property, plant, and equipment assets as of December 31, 2025 and 2024.

Impairment of Long-Lived Assets

Long-lived assets are reviewed for indications of possible impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by comparison of the carrying amounts to the future undiscounted cash flows attributable to these assets. An impairment loss is recognized to the extent an asset group is not recoverable, and the carrying amount exceeds the fair value. The Company recognized a $2.6 million impairment loss for the year ended December 31, 2023 related to its leased office space in Austin, Texas (see Note 11 and Note 17 for additional information). There were no impairments of long-lived assets for the years ended December 31, 2025 and 2024.

Accrued Research and Development Costs

The Company records the costs associated with research nonclinical studies, clinical trials, and manufacturing development as incurred. These costs are a significant component of the Company’s research and development expenses, with a substantial portion of the Company’s on-going research and development activities conducted by third-party service providers, including contract research organizations ("CROs") and contract manufacturing organizations ("CMOs"), and the Company's related-party Paragon.

The Company accrues for expenses resulting from obligations under the Paragon Agreement and agreements with CROs, CMOs, and other outside service providers for which payment flows do not match the periods over which materials or services are provided to the Company. Accruals are recorded based on estimates of services received and efforts expended pursuant to agreements established with Paragon, CROs, CMOs, and other outside service providers. These estimates are typically based on contracted amounts applied to the proportion of work performed and determined through analysis with internal personnel and external service providers as to the progress or stage of completion of the services. The Company makes significant judgments and estimates in determining the accrual balance in each reporting period. In the event advance payments are made to Paragon, a CRO, CMO, or outside service provider, the payments will be recorded as a prepaid asset which will be amortized as the contracted services are performed. As actual costs become known, the Company adjusts its accruals. Inputs, such as the services performed, the number of patients enrolled, or the trial duration, may vary from the Company’s estimates, resulting in adjustments to research and development expense in future periods. Changes in these estimates that result in material changes to the Company’s accruals could materially affect the Company’s results of operations. Historically, the Company has not experienced any material deviations between accrued and actual research and development expenses.

License Agreements Contingent Milestone Payments

The Company’s license agreements include specific development, regulatory, and clinical milestone payments that are payable upon the resolution of a contingency, such as upon the selection of a development candidate, first dosing of a human patient in clinical trials or receipt of the U.S. Food Drug and Administration’s (“FDA”) approval of a Spyre drug. The achievement of these milestone payments involves many factors outside of the Company’s control and therefore the associated likelihood cannot be considered probable until the related contingency is resolved. Based on the preceding, the Company accrues each milestone payment upon the achievement of the applicable milestone event.

Leases

The Company determines if an arrangement is a lease at inception. Right-of-use ("ROU") assets represent the Company's right to use an underlying asset for the lease term and lease liabilities represent the Company's obligation to make lease payments arising from the lease. The classification of the Company's leases as operating or finance leases along with the initial measurement and recognition of the associated ROU assets and lease liabilities is performed at the lease commencement date. The measurement of lease liabilities is based on the present value of future lease payments over the lease term. As the Company's leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the lease commencement date in determining the present value of future lease payments. To determine the incremental borrowing rate, the Company uses the lease-term appropriate current treasury bond rates adjusted for collateral and inflation risks combined with quoted bank financing rates. The ROU asset is based on the measurement of the lease liability and also includes any lease payments made prior to or on lease commencement and excludes lease incentives and initial direct costs incurred, as applicable. The lease terms may include options to extend or terminate the lease when it is reasonably certain the Company will exercise any such options. Rent expense for the Company's operating leases is recognized on a straight-line basis over the lease term. Amortization expense for the ROU asset associated with its finance leases is recognized on a straight-line basis over the term of the lease and interest expense associated with its finance leases is recognized on the balance of the lease liability using the effective interest method based on the estimated incremental borrowing rate.

As described in Note 11, the Company had lease agreements with lease and non-lease components prior to its restructuring. As allowed under Topic 842, the Company elected to not separate lease and non-lease components for any leases involving real estate and office equipment classes of assets and, as a result, accounted for the lease and non-lease components as a single lease component. The Company also elected to not apply the recognition requirement of Topic 842 to leases with a term of 12 months or less for all classes of assets. As of December 31, 2025 and 2024, the Company had no operating or finance lease obligations.

Fair Value of Financial Instruments

The Company uses fair value measurements to record fair value adjustments to certain financial and non-financial assets and liabilities and to determine fair value disclosures. The accounting standards define fair

value, establish a framework for measuring fair value, and require disclosures about fair value measurements. Fair value is defined as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining the fair value measurements for assets and liabilities required to be recorded at fair value, the principal or most advantageous market in which the Company would transact are considered along with assumptions that market participants would use when pricing the asset or liability, such as inherent risk, transfer restrictions, and risk of nonperformance.

The accounting standard for fair value establishes a fair value hierarchy based on three levels of inputs, the first two of which are considered observable and the last unobservable, that requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. A financial instrument’s categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement.

The three levels of inputs that may be used to measure fair value are as follows:


Level 1:			Observable inputs, such as quoted prices in active markets for identical assets or liabilities.

Level 2:			Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3:			Valuations based on unobservable inputs to the valuation methodology and including data about assumptions that market participants would use in pricing the asset or liability based on the best information available under the circumstances.

Financial instruments carried at fair value include cash equivalents and marketable securities. The carrying amounts of accounts payable and accrued liabilities approximate fair value due to their relatively short maturities.

Revenue Recognition

Under ASC Topic 606, “Revenue from Contracts with Customers” (“Topic 606”), an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation.

The Company assesses its license arrangements within the scope of Topic 606 in accordance with this framework as follows:

License revenue

The Company assesses whether the goods or services promised within each contract are distinct to identify those that are performance obligations. This assessment involves subjective determinations and requires management to make judgments about the individual promised goods or services and whether such are separable from the other aspects of the contractual relationship. In assessing whether a promised good or service is distinct, and therefore a performance obligation, the Company considers factors such as the research, stage of development of the licensed product, manufacturing and commercialization capabilities of the customer and the availability of the associated expertise in the general marketplace. The Company also considers the intended benefit of the contract in assessing whether a promised good or service is separately identifiable from other promises in the contract. If a promised good or service is not distinct, the Company is required to combine that good or service with other promised goods or services until it identifies a bundle of goods or services that is distinct. Arrangements that include rights to additional goods or services that are exercisable at a customer’s

discretion are generally considered options. The Company assesses if these options provide a material right to the customer and if so, they are considered performance obligations.

The transaction price is determined and allocated to the identified performance obligations in proportion to their stand-alone selling prices (“SSP”) on a relative SSP basis. SSP is based on observable prices of the performance obligations or, when such prices are not observable, are estimated. The estimation of SSP may include factors such as forecasted revenues or costs, development timelines, discount rates, probabilities of technical and regulatory success, and considerations such as market conditions and entity-specific factors. In certain circumstances, the Company may apply the residual method to determine the SSP of a good or service if the SSP is considered highly variable or uncertain. The Company validates the SSP for performance obligations by evaluating whether changes in the key assumptions used to determine the SSP will have a significant effect on the allocation of arrangement consideration between multiple performance obligations.

If the consideration promised in a contract includes a variable amount, the Company estimates the amount of consideration to which it will be entitled in exchange for transferring the promised goods or services to a customer. The Company determines the amount of variable consideration by using the expected value method or the most likely amount method. The Company includes the amount of estimated variable consideration in the transaction price to the extent that it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, the Company re-evaluates the estimated variable consideration included in the transaction price and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis in the period of adjustment.

If an arrangement includes development, regulatory or commercial milestone payments, the Company evaluates whether the milestones are considered likely of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant cumulative revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are generally not considered likely of being achieved until those approvals are received.

In determining the transaction price, the Company adjusts consideration for the effects of the time value of money if the timing of payments provides the Company with a significant benefit of financing. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the licensee and the transfer of the promised goods or services to the licensees will be one year or less. For arrangements with licenses of intellectual property that include sales-based royalties, including milestone payments based on the level of sales, and if the license is deemed to be the predominant item to which the royalties relate, the Company recognizes royalty revenue and sales-based milestones at the later of (i) when the related sales occur, or (ii) when the performance obligation to which the royalty has been allocated has been satisfied.

The Company recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) each performance obligation is satisfied at a point in time or over time, and if over time, recognition is based on the use of an output or input method.

The Company’s contracts may be modified for changes in the customer’s requirements. If contract modifications are for additional goods and services that are distinct from the existing contract, the modification will be accounted for as either a separate contract or a termination of the existing contract, depending on whether the additional goods or services reflects the SSP.

If the additional goods or services in a contract modification are not distinct from the existing contract, they are accounted for as if they were part of the original contract. The effect of the contract modification on the transaction price and the measure of progress for the performance obligation to which it relates is recognized as an adjustment to revenue on a cumulative catch-up basis. The cumulative catch-up adjustment is calculated using an updated measure of progress applied to the sum of (1) the remaining consideration allocated to the partially satisfied performance obligation and (2) the revenue already recognized on that performance obligation. The revenue recognized for fully satisfied goods or services and distinct from the remaining performance obligations is not altered by the modification.

Collaborative arrangements

The Company analyzes its license arrangements to assess whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities and therefore within the scope of ASC Topic 808, Collaborative Arrangements (“Topic 808”). This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement. For arrangements within the scope of Topic 808 that contain multiple elements, the Company first determines which elements of the collaboration are deemed to be within the scope of Topic 808 and which elements of the collaboration are more reflective of a vendor-customer relationship and therefore within the scope of Topic 606. For elements of collaboration arrangements that are accounted for pursuant to Topic 808, an appropriate recognition method is determined and applied consistently, either by analogy to authoritative accounting literature or by applying a reasonable and rational policy election. For those elements of the arrangement that are accounted for pursuant to Topic 606, the Company applies the five-step model described above.

Research and Development Costs

Research and development costs are expensed as incurred. Research and development costs include, but are not limited to, salaries, benefits, travel, stock-based compensation, consulting costs, contract research service costs, laboratory supplies and facilities, contract manufacturing costs, and costs paid to other third parties that conduct research and development activities on the Company’s behalf. Amounts incurred in connection with license agreements are also included in research and development expense.

Advance payments for goods or services to be rendered in the future for use in research and development activities are recorded as a prepaid asset and expensed as the related goods are delivered or the services are performed.

Stock-Based Compensation

The Company recognizes the cost of stock-based awards granted to employees and non-employees based on the estimated grant-date fair values of the awards. The fair values of stock options are estimated on the date of grant using the Black-Scholes option pricing model. The fair values of restricted stock units (“RSUs”) are based on the fair value of the Company’s common stock on the date of the grant. The value of the award is recognized as compensation expense on a straight-line basis over the requisite service period. Forfeitures are recognized when they occur, which may result in the reversal of compensation costs in subsequent periods as the forfeitures arise. Compensation expense for employee and non-employee share-based payment awards with performance conditions is recognized when the performance condition is deemed probable.

Convertible Preferred Stock Issued through PIPE

The Company records shares of convertible preferred stock at their respective fair values on the dates of issuance, net of issuance costs. The Company classified the Series B Preferred Stock outside of stockholders’ equity at issuance because if conversion to common stock was not approved by the stockholders, the Series B Preferred Stock was redeemable at the option of the holders for cash equal to the closing price of the Company's common stock on the last trading day prior to the holder’s redemption request. The Company determined that the conversion and redemption was outside of the Company’s control. Additionally, the Company determined the Series B Preferred Stock did not contain any embedded derivatives and therefore the conversion and redemption features did not require bifurcation.

Since the Series B Preferred Stock is no longer redeemable, the associated balances of the Series B Preferred Stock were reclassified from mezzanine equity to permanent equity during the second quarter of 2024.

Contingent Milestone Proceeds

The Company recognizes contingent milestone proceeds associated from the sale of in-process research and development assets in earnings once the achievement of the milestone becomes probable and payment to the Company is contractually required.

Acquisitions

The Company evaluates acquisitions of assets and other similar transactions to assess whether or not the transaction should be accounted for as a business combination or asset acquisition by first applying a screen test to determine whether substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets. If so, the transaction is accounted for as an asset acquisition. If not, further determination is required as to whether or not the Company has acquired inputs and processes that have the ability to create outputs, which would meet the definition of a business. Significant judgment is required in the application of the test to determine whether an acquisition is a business combination or an acquisition of assets.

Acquisitions meeting the definition of business combinations are accounted for using the acquisition method of accounting, which requires that the purchase price be allocated to the net assets acquired at their respective fair values. In a business combination, any excess of the purchase price over the estimated fair values of the net assets acquired is recorded as goodwill.

The Company measures and recognizes asset acquisitions that are not deemed to be business combinations based on the cost to acquire the assets, which includes pre-acquisition direct costs recorded in accrued professional and consulting fees. Goodwill is not recognized in asset acquisitions. When a transaction accounted for as an asset acquisition includes an IPR&D asset, the IPR&D asset is only capitalized if it has an alternative future use other than in a particular research and development project. Otherwise, the cost allocated to acquire an IPR&D asset with no alternative future use is charged to expense at the acquisition date.

Contingent Value Rights

The Company evaluates its contracts to determine if those contracts qualify as derivatives under ASC 815, Derivatives and Hedging (“ASC 815”). For derivative financial instruments that are accounted for as liabilities, the derivative instrument is initially recorded at its fair value and is then re-valued at each reporting date. Any changes in fair value are recorded as other income or expense for each reporting period. Derivative instrument liabilities are classified in the balance sheet as current or non-current based on whether or not net-cash settlement of the derivative instrument is probable within the next 12 months from the balance sheet date. The Company determined that certain contingent payments under the CVR Agreement qualified as derivatives under ASC 815, and as such, were recorded as a liability on the balance sheet. This value is then remeasured for future expected payout as well as the increase in fair value due to the time value of money. These gains or losses, if any, are recognized in the consolidated statements of operations and comprehensive loss within Other (expense) income, net.

The Company applies a scenario-based method and weighs them based on the possible achievement of certain milestones. The milestone payments are contingent on formal reimbursement decisions by national authorities in key European markets and pegzilarginase approval by the FDA, among other events. This fair value measurement is based on significant inputs not observable in the market and thus represents a Level 3 measurement as defined in ASC 820, Fair Value Measurement. The key assumptions used include the discount rate, probability of regulatory success, reimbursement rates from certain government agencies and estimated cash flow dates. The estimated value of the CVR consideration is based upon available information and certain assumptions which the Company's management believes are reasonable under the circumstances. The ultimate payout under the CVRs may differ materially from the assumptions used in determining the fair value of the CVR consideration.

Income Taxes

The Company uses the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are recognized for the expected future tax consequences of temporary differences between the financial statements and the tax bases of assets and liabilities. Additionally, any changes in income tax laws are immediately recognized in the year of enactment.

A valuation allowance is established against the deferred tax assets to reduce their carrying value to an amount that is more likely than not to be realized. The deferred tax assets and liabilities are classified as

noncurrent along with the related valuation allowance. Due to a lack of earnings history, the net deferred tax assets have been fully offset by a valuation allowance.

The Company recognizes benefits of uncertain tax positions if it is more likely than not that such positions will be sustained upon examination based solely on the technical merits, as the largest amount of benefits that is more likely than not to be realized upon the ultimate settlement. The Company’s policy is to recognize interest and penalties related to the unrecognized tax benefits as a component of income tax expense, if applicable. As of December 31, 2025 and 2024, the Company had no unrecognized tax benefits and there were no interest or penalties incurred by the Company in the years ended December 31, 2025, 2024, or 2023.

Comprehensive Loss

Comprehensive loss is the change in stockholders’ equity from transactions and other events and circumstances other than those resulting from investments by stockholders and distributions to stockholders. The Company’s other comprehensive income (loss) is currently comprised of changes in unrealized losses and gains on available-for-sale securities and foreign currency translation adjustments reflecting the cumulative effect of changes in exchange rates between the foreign entity’s functional currency and the reporting currency.

Recently Adopted Accounting Pronouncements

In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740) - Improvements to Income Tax Disclosures, to require enhanced income tax disclosures to provide information to assess how an entity’s operations and related tax risks, tax planning, and operational opportunities affect its tax rate and prospects for future cash flows. The amendments in this update provide that a business entity disclose (1) a tabular income tax rate reconciliation, using both percentages and amounts, (2) separate disclosure of any individual reconciling items that are equal to or greater than 5% of the amount computed by multiplying the income (loss) from continuing operations before income taxes by the applicable statutory income tax rate, and disaggregation of certain items that are significant and (3) amount of income taxes paid (net of refunds received) disaggregated by federal, state and foreign jurisdictions, including separate disclosure of any individual jurisdictions greater than 5% of total income taxes paid. These amendments are effective for the Company for annual periods in beginning in 2025, applied prospectively, with early adoption and retrospective application permitted. The Company applied the amendments prospectively for the year ended December 31, 2025, and the impact of the adoption of the amendments in this update was not material to the Company’s consolidated financial position and results of operations since the amendments require only enhancement of existing income tax disclosures in the footnotes to the Company’s consolidated financial statements. See Note 18, Income Taxes.

Not Yet Adopted Accounting Pronouncements

In November 2024, the FASB issued ASU 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses to improve disclosures about public business entities’ expenses and to provide more detailed information around the types of expenses included in commonly presented expense captions. ASU 2024-03 is effective for fiscal years beginning after December 15, 2026, and interim periods for fiscal years beginning after December 15, 2027, and can be applied on a prospective basis or on a retrospective basis to all periods presented. Early adoption is permitted. This ASU will have no impact on the Company’s consolidated financial condition or results of operations. The Company is currently evaluating the impact of adopting ASU 2024-03 on its disclosures.

In December 2025, the FASB issued ASU No. 2025-11, Interim Reporting (Topic 270): Narrow-Scope Improvements. The ASU clarifies interim disclosure requirements and the applicability of Topic 270. The objective of the amendments is to provide further clarity about the current interim disclosure requirements. The ASU is effective for interim reporting periods within annual reporting periods beginning after December 15,

2027. Adoption of this ASU can be applied either a prospective or a retrospective approach. Early adoption is permitted. The Company is currently evaluating the impact of adopting ASU 2024-03 on its disclosures.

In December 2025, the FASB issued ASU No. 2025-12, Codification Improvements. The update represents changes to the Codification that clarify, correct errors in or make other improvements to a variety of topics that are intended to make it easier to understand and apply. Generally, the amendments in this Update are not intended to result in significant changes for most entities. The ASU is effective for interim reporting periods within annual reporting periods beginning after December 15, 2026. The adoption method of this ASU may vary, on an issue-by-issue basis. Early adoption is permitted. The Company is currently evaluating the impact of adopting ASU 2024-03 on its disclosures.

Asset Acquisition - Narrative (Details) - Spyre Therapeutics, Inc. $ / shares in Units, $ in Millions	Jun. 22, 2023 USD ($) $ / shares shares
Asset Acquisition [Line Items]
Cost to acquire asset \| $	$ 113.2
Asset acquisition consideration transferred issuable shares of common stock on an as-converted basis (in shares)	14,595,480
Spyre 2023 Equity Incentive Plan
Asset Acquisition [Line Items]
Number of outstanding and unexercised stock options to purchase (in shares)	2,734
Series A Non-Voting Convertible Preferred Stock
Asset Acquisition [Line Items]
Shares transferred as equity interest in asset acquisition (in shares)	364,887
Shares issued, price per share (in dollars per share) \| $ / shares	$ 291.08
Common Stock
Asset Acquisition [Line Items]
Shares transferred as equity interest in asset acquisition (in shares)	517,809
Shares issued, price per share (in dollars per share) \| $ / shares	$ 7.277

Cover - USD ($) $ in Billions	12 Months Ended
Cover - USD ($) $ in Billions	Dec. 31, 2025	Feb. 12, 2026	Jun. 30, 2025
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2025
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-37722
Entity Registrant Name	SPYRE THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-4312787
Entity Address, Address Line One	221 Crescent Street
Entity Address, Address Line Two	Building 23, Suite 105
Entity Address, City or Town	Waltham
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02453
City Area Code	617
Local Phone Number	651-5940
Title of 12(b) Security	Common Stock, $0.0001 Par Value Per Share
Trading Symbol	SYRE
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction	false
Entity Shell Company	false
Entity Public Float			$ 1.1
Entity Common Stock Shares Outstanding		78,540,164
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the Registrant’s Definitive Proxy Statement (“Proxy Statement”) relating to the 2026 Annual Meeting of Stockholders will be filed with the Commission within 120 days after the end of the Registrant’s 2025 fiscal year and is incorporated by reference into Part III of this Report.
Entity Central Index Key	0001636282
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	FY
Amendment Flag	false

Restructuring Charges (Tables)

12 Months Ended

Dec. 31, 2025

Restructuring and Related Activities [Abstract]

Schedule of Charges Related to the Restructuring Activities

A summary of the charges related to the restructuring activities is as follows (in thousands):


	Severance Related Expenses		Stock Compensation Expenses		Loss on Disposal of Long-Lived Assets		Lease Asset Impairment		Total Restructuring Costs
Research and development	$	3,182	$	123	$	749	$	1,405	$	5,459
General and administrative	3,266		870		182		1,175		5,493
Total	$	6,448	$	993	$	931	$	2,580	$	10,952

Accrued and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Accrued Liabilities and Other Liabilities [Abstract]
Accrued compensation	$ 7,940	$ 5,688
Accrued contracted research and development costs	17,424	20,861
Accrued professional and consulting fees	1,404	661
Other	179	501
Total accrued and other current liabilities	$ 26,947	$ 27,711

Segment Reporting - Narrative (Details)	12 Months Ended
Segment Reporting - Narrative (Details)	Dec. 31, 2025 segment
Segment Reporting [Abstract]
Number of operating segments	1
Number of reportable segments	1

Related Party Transactions - Schedule of Related Party Accounts Payable (Details) - Related Party - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Related Party Transaction [Line Items]
Total related party accounts payable	$ 0.0	$ 0.6
Reimbursable costs under the Paragon Agreement
Related Party Transaction [Line Items]
Total related party accounts payable	0.0	0.1
License Agreements development milestone liability (see Note 9)
Related Party Transaction [Line Items]
Total related party accounts payable	$ 0.0	$ 0.5

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2025

Share-Based Payment Arrangement [Abstract]

Schedule of Employee and Non-Employee Stock Option Activity

The following table summarizes stock option activity for the year ended December 31, 2025:


	Shares Issuable Under Options	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term	Aggregate Intrinsic Value
				(in years)	(in thousands)
Outstanding as of December 31, 2024	9,253,158	$	15.08	8.80	$	90,016
Granted	2,623,217	19.98
Exercised	(307,673)	8.68
Forfeited	(198,455)	33.38
Outstanding as of December 31, 2025	11,370,247	$	16.06	8.16	$	191,198
Options vested and expected to vest as of December 31, 2025	11,370,247	$	16.06	8.16	$	191,198
Options exercisable as of December 31, 2025	5,164,959	$	14.50	7.95	$	95,153

Schedule of Employee Restricted Stock Activity

The following table summarizes employee restricted stock unit activity for the year ended December 31, 2025:


	Shares	Weighted Average Grant Date Fair Value
Unvested restricted stock units as of December 31, 2024	115,398	$	18.17

Vested	(38,466)	18.17

Unvested restricted stock units as of December 31, 2025	76,932	$	18.17

Schedule of Stock-Based Compensation Expense

Total stock-based compensation expense recognized from the Parapyre Option Obligation, the Company’s equity incentive plans, 2018 Plan, and the 2016 ESPP for the years ended December 31, 2025, 2024, and 2023 was as follows (in thousands):


	Year Ended December 31,
	2025				2024				2023
	Employees		Non- Employees		Employees		Non- Employees		Employees		Non- Employees
Research and development (1)	$	16,270	$	—	$	9,112	$	14,459	$	2,910	$	11,328
General and administrative	20,318		1,026		19,833		1,429		11,327		110
Total stock-based compensation expense (2)	$	36,588	$	1,026	$	28,945	$	15,888	$	14,237	$	11,438

(1)For the years ended December 31, 2024 and 2023, $14.5 million and $11.4 million, respectively, was recognized as stock compensation expense related to the Parapyre Option Obligation. There was no such expense for the year ended December 31, 2025.

(2)Of the total $36.6 million, $28.9 million and $14.2 million of employee related stock-based compensation expense for the years ended December 31, 2025, 2024 and 2023, respectively, nil, $3.6 million and $8.3 million is related to legacy Aeglea employees and directors who no longer served the Company as of the end of the respective period.

Schedule of Weighted-Average Assumptions Used in Calculating Fair Value of Awards

The following table summarizes the weighted-average assumptions used in calculating the fair value of the awards:


	Year Ended December 31,
	2025		2024		2023
Stock Options Granted
Expected term (in years)	5.99		6.03		5.88
Expected volatility	76	%	105	%	107	%
Risk-free interest	4.33	%	4.06	%	4.37	%
Dividend yield	0	%	0	%	0	%
2016 ESPP
Expected term (in years)	0.44		0.50		0.49
Expected volatility	70	%	84	%	181	%
Risk-free interest	4.22	%	5.16	%	4.99	%
Dividend yield	0	%	0	%	0	%

Leases - Schedule of Lease Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Leases [Abstract]
Operating lease cost	$ 0	$ 0	$ 455
Variable lease cost	0	0	471
Total lease cost	$ 0	$ 0	$ 926

Cash Equivalents and Marketable Securities

12 Months Ended

Dec. 31, 2025

Cash and Cash Equivalents [Abstract]

Cash Equivalents and Marketable Securities

The following tables summarize the estimated fair value of the Company’s cash equivalents and marketable securities and the gross unrealized gains and losses (in thousands):


	December 31, 2025
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Cash equivalents:
Money market funds	$	74,004	$	—	$	—	$	74,004
Commercial paper	9,987		—		—		9,987

Total cash equivalents	$	83,991	$	—	$	—	$	83,991

Marketable securities:
Commercial paper	$	184,423	$	25	$	(80)	$	184,368
Corporate bonds	100,753		60		(23)		100,790
U.S. government treasury securities	265,316		748		—		266,064
U.S. government agency securities	119,450		153		(13)		119,590
Total marketable securities	$	669,942	$	986	$	(116)	$	670,812


	December 31, 2024
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Cash equivalents:
Money market funds	$	65,902	$	—	$	—	$	65,902
Commercial paper	21,832		6		—		21,838
U.S. government treasury securities	—		—		—		—
Total cash equivalents	$	87,734	$	6	$	—	$	87,740

Marketable securities:
Commercial paper	$	143,265	$	104	$	(77)	$	143,292
Corporate bonds	56,471		25		(48)		56,448
U.S. government treasury securities	227,155		385		(296)		227,244
U.S. government agency securities	86,616		137		(72)		86,681
Total marketable securities	$	513,507	$	651	$	(493)	$	513,665

The following table summarizes the available-for-sale securities in an unrealized loss position for which an allowance for credit losses has not been recorded as of December 31, 2025 and 2024, aggregated by major security type and length of time in a continuous unrealized loss position:


	December 31, 2025
	Less Than 12 Months				12 Months or Longer				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Commercial paper	$	99,837	$	(80)	$	—	$	—	$	99,837	$	(80)
Corporate bonds	58,296		(23)		—		—		58,296		(23)

U.S. government agency securities	22,828		(13)		—		—		22,828		(13)
Total marketable securities	$	180,961	$	(116)	$	—	$	—	$	180,961	$	(116)


	December 31, 2024
	Less Than 12 Months				12 Months or Longer				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Commercial paper	$	67,200	$	(77)	$	—	$	—	$	67,200	$	(77)
Corporate bonds	42,916		(48)		—		—		42,916		(48)
U.S. government treasury securities	126,588		(296)		—		—		126,588		(296)
U.S. government agency securities	12,560		(72)		—		—		12,560		(72)
Total marketable securities	$	249,264	$	(493)	$	—	$	—	$	249,264	$	(493)

The Company evaluated its securities for credit losses and considered the decline in market value to be primarily attributable to current economic and market conditions and not to a credit loss or other factors. Additionally, the Company does not intend to sell the securities in an unrealized loss position and does not expect they will be required to sell the securities before recovery of the unamortized cost basis. As of December 31, 2025 and 2024, an allowance for credit losses had not been recognized. Given the Company's intent and ability to hold such securities until recovery, and the lack of significant change in credit risk of these investments, the Company does not consider these marketable securities to be impaired as of December 31, 2025 and 2024.

There were $0.7 million and $0.3 million net unrealized gains on marketable securities for the years ended December 31, 2025 and 2023, respectively, and $0.1 million net unrealized losses for the year ended

December 31, 2024. There were no realized gains on marketable securities for the years ended December 31, 2025, 2024 and 2023.

Interest on marketable securities is included in interest income. Accrued interest receivable on available-for-sale debt securities totaled $4.5 million and $3.4 million as of December 31, 2025 and 2024, respectively, and is excluded from the estimate of credit losses.

The following table summarizes the contractual maturities of the Company's marketable securities at estimated fair value (in thousands):


	December 31,
	2025		2024
Due in one year or less	$	440,895	$	338,442
Due in 1 - 2 years	229,917		175,223
Total marketable securities	$	670,812	$	513,665

The Company may sell investments at any time for use in current operations even if they have not yet reached maturity. As a result, the Company classifies marketable securities, including securities with maturities beyond twelve months, as current assets.

Stock-Based Compensation - Schedule of Employee Restricted Stock Activity (Details) - Restricted Common Stock - Employees	12 Months Ended
	Dec. 31, 2025 $ / shares shares
Shares
Unvested (in shares) \| shares	115,398
Vested (in shares) \| shares	(38,466)
Unvested (in shares) \| shares	76,932
Weighted Average Grant Date Fair Value
Unvested (in dollars per share) \| $ / shares	$ 18.17
Vested (in dollars per share)) \| $ / shares	18.17
Unvested (in dollars per share) \| $ / shares	$ 18.17

Asset Acquisition

12 Months Ended

Dec. 31, 2025

Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract]

Asset Acquisition

On June 22, 2023, the Company acquired Pre-Merger Spyre pursuant to the Acquisition Agreement, by and among the Company, First Merger Sub, Second Merger Sub and Pre-Merger Spyre. Pursuant to the Acquisition Agreement, First Merger Sub merged with and into Pre-Merger Spyre, pursuant to which Pre-Merger Spyre was the surviving corporation and became the Company's wholly owned subsidiary (the “First Merger”). Immediately following the First Merger, Pre-Merger Spyre merged with and into Second Merger Sub, pursuant to which Second Merger Sub became the surviving entity. Pre-Merger Spyre was a pre-clinical stage biotechnology company that was incorporated on April 28, 2023 under the direction of Peter Harwin, a Managing Member of Fairmount, for the purpose of holding rights to certain intellectual property being developed by Paragon. Fairmount is a founder of Paragon.

With respect to the Asset Acquisition, the Company determined that Aeglea was the acquirer for accounting purposes under ASC 805. The primary factors considered were a) the relative voting rights in the combined entity not resulting in a change of control, b) legacy members of the Company's Board of Directors maintained control of the Board of Directors, and c) the only change in the composition of senior management was the appointment of a new Chief Operating Officer. Next, the Company considered whether the Asset Acquisition should be defined as a business under ASC 805. ASC 805-10-55-5A through 55-5C describe a screen test to determine whether an acquired set of assets and activities is not a business. We determined that substantially all (greater than 90%) of the fair value of the assets acquired were concentrated in a single asset, Spyre’s Option to license intellectual property rights related to SPY001, SPY002, SPY003 and an additional research program pursuant to the Paragon Agreement. Accordingly, the Company treated the Asset Acquisition as an asset acquisition for accounting purposes. Even if the transaction would have failed the screen test, Pre-Merger Spyre lacked the financial resources to have inputs, processes, and outputs to constitute a business under ASC 805.

The Company completed the Asset Acquisition of Pre-Merger Spyre, in accordance with the terms of the Acquisition Agreement. Under the terms of the Acquisition Agreement, the Company issued 517,809 shares of common stock and 364,887 shares of Series A Preferred Stock to former Pre-Merger Spyre security holders. In addition, outstanding and unexercised stock options to purchase 2,734 shares of common stock were assumed from the Amended and Restated Spyre 2023 Equity Incentive Plan.

At the acquisition date, the Company recorded forward contracts to represent the obligation to issue shares of the Company's common stock and shares of Series A Preferred Stock. The forward contract related to the common stock was recorded as Additional paid-in capital as the instrument is indexed to the Company's common stock. The forward contract related to the Series A Preferred Stock was recorded as a liability, as the underlying stock has a cash redemption feature. On July 7, 2023, both the shares of common stock and Series A Preferred Stock were issued and the forward contract liability associated with the Series A Preferred Stock was settled accordingly.

The Company concluded that the arrangement meets the definition of an asset acquisition rather than a business combination, as substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset, the Option to exclusively license IPR&D. The Company determined that the Option to license IPR&D was a single asset as the Company's strategy relies on developing the entire portfolio of individual treatments to create combination treatments that simultaneously address different mechanisms of

irritable bowel disease with a single treatment. The Company also determined that the pipeline candidates within the portfolio are similar in nature and risk profile. In addition, the Company did not obtain any substantive processes, assembled workforce, or employees capable of producing outputs in connection with the Asset Acquisition.

The Company determined that the cost to acquire the asset was $113.2 million which was recorded as acquired IPR&D. The fair value of the consideration issued consisted of the 364,887 shares of Series A Preferred Stock (14,595,480 shares of common stock on an as-converted basis) and 517,809 shares of common stock, valued at $291.08 per share and $7.277 per share, respectively.

The Asset Acquisition costs are shown on the following table (in millions):


	June 22, 2023
Consideration transferred in Series A Preferred Stock and common stock	$	110.0
Transaction costs incurred by the Company	3.2
Total cost to acquire asset	$	113.2

The allocation of the purchase price to net assets acquired is as a follows:


	June 22, 2023
Acquired in-process research and development	$	130.2
Cash acquired	3.0
Assumed liabilities	(20.0)
Total cost to acquire asset	$	113.2

The Company and Basis of Presentation	12 Months Ended
The Company and Basis of Presentation	Dec. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company and Basis of Presentation	The Company and Basis of Presentation Spyre Therapeutics, Inc., formerly Aeglea BioTherapeutics, Inc., (“Spyre” or the “Company”) is a clinical stage biotechnology company focused on developing next generation therapeutics for patients living with inflammatory bowel disease and other immune-mediated diseases. The Company was formed as a Limited Liability Company ("LLC") in Delaware on December 16, 2013 under the name Aeglea BioTherapeutics Holdings, LLC and was converted from a Delaware LLC to a Delaware corporation on March 10, 2015. On November 27, 2023, the Company completed its corporate rebranding, changing the name of the Company to Spyre Therapeutics, Inc. The Company operates in one segment and has its principal offices in Waltham, Massachusetts. On September 8, 2023, the Company effected a reverse stock split of its common stock at a ratio of 1-for-25 (the “Reverse Split”). Except as indicated otherwise, all share numbers related to the Company's common stock disclosed in these financial statements have been adjusted on a post-Reverse Split basis. On April 12, 2023, based on the review of the inconclusive interim results from the Company's Phase 1/2 clinical trial of pegtarviliase for the treatment of Classical Homocystinuria and other business considerations, the Company announced that it had initiated a process to explore strategic alternatives to maximize stockholder value and engaged an independent exclusive financial advisor to support this process. As a result, in April 2023, the Company implemented a restructuring plan resulting in an approximate 83% reduction of the Company’s existing headcount. On June 22, 2023, the Company acquired, in accordance with the terms of the Agreement and Plan of Merger (the "Acquisition Agreement"), the assets of Spyre Therapeutics, Inc. (“Pre-Merger Spyre”) as disclosed in Note 7 and 8, a privately held biotechnology company advancing a pipeline of antibody therapeutics with the potential to transform the treatment of inflammatory bowel disease through a research and development option agreement ("Paragon Agreement") with Paragon Therapeutics ("Paragon"). The asset acquisition was accomplished through a two-step reverse triangular merger whereby Aspen Merger Sub I, Inc., a Delaware corporation and a wholly owned subsidiary of the Company ("First Merger Sub"), merged with and into Pre-Merger Spyre, which existed at the time the Acquisition Agreement was entered into, became a wholly owned subsidiary of the Company in accordance with the terms of the Acquisition Agreement. Immediately following this merger, Pre-Merger Spyre merged with and into Sequoia Merger Sub II, LLC, a Delaware limited liability company and a wholly subsidiary of the Company (“Second Merger Sub”), in accordance with the terms of the Acquisition Agreement and Pre-Merger Spyre ceased to exist. Subsequently, Aeglea BioTherapeutics, Inc. was renamed Spyre Therapeutics, Inc. and is a different entity than Pre-Merger Spyre, which ceased to exist upon merging with Second Merger Sub. The transaction was structured as a stock-for-stock transaction pursuant to which all of Pre-Merger Spyre's outstanding equity interests were exchanged based on a fixed exchange ratio of 0.5494488 to 1 for consideration from the Company of 517,809 shares of common stock and 364,887 shares of Series A non-voting convertible preferred stock, par value of $0.0001 per share ("Series A Preferred Stock") (convertible on a 40 to 1 basis), in addition to the assumption of outstanding and unexercised stock options to purchase 2,734 shares of common stock from the Amended and Restated Spyre 2023 Equity Incentive Plan (the "Asset Acquisition"). The common stock and Series A Preferred Stock related to the Asset Acquisition were issued to the Pre-Merger Spyre stockholders on July 7, 2023. For additional information, see Note 7. In connection with the Asset Acquisition, on June 26, 2023, the Company completed a private placement of shares of Series A Preferred Stock (the “June 2023 PIPE” and, together with the Asset Acquisition, the "June 2023 Transactions") to a group of investors (the “June 2023 Investors”). The Company sold an aggregate of 721,452 shares of Series A Preferred Stock (the “June 2023 PIPE Securities”) at $291.08 per share for net proceeds of $197.3 million after deducting approximately $12.7 million of placement agent and other offering expenses. For additional information, see Note 12. In connection with the Asset Acquisition, a non-transferable contingent value right ("CVR") was distributed to stockholders of record of the Company as of the close of business on July 3, 2023 (the "Legacy Stockholders"), but was not distributed to the holders of shares of common stock or Series A Preferred Stock issued to the former stockholders of Pre-Merger Spyre or June 2023 Investors in the June 2023 Transactions. Holders of the CVRs will be entitled to receive certain cash payments from proceeds received by the Company prior to the third anniversary of the CVR Agreement, if any, related to the disposition or monetization of its legacy assets during the one-year period following the closing of the Asset Acquisition. For additional information, see Note 3. On November 21, 2023, the Company's stockholders approved the conversion of the Company's Series A non-voting convertible preferred stock to common stock. For additional information, see Note 12. On December 11, 2023, the Company completed a private placement of shares of common stock and Series B non-voting convertible preferred stock, par value of $0.0001 per share ("Series B Preferred Stock") (convertible on a 40 to 1 basis) (collectively, the “December 2023 PIPE”) to a group of investors (the “December 2023 PIPE Investors”). The Company sold an aggregate of 6,000,000 shares of its common stock at an offering price of $15.00 per share and 150,000 shares of Series B Preferred Stock (the “December 2023 PIPE Securities”) at $600.00 per share for net proceeds of approximately $169.1 million after deducting approximately $10.9 million of placement agent and other offering expenses. For additional information, see Note 12. On March 20, 2024, the Company completed a private placement of Series B Preferred Stock (convertible on a 40 to 1 basis) (the “March 2024 PIPE”) to a group of investors. The Company sold 121,625 shares of Series B Preferred Stock at $1,480 per share. The net proceeds from this offering were approximately $168.9 million after deducting placement and offering costs of $11.2 million. On April 23, 2024, the Company entered into an exchange agreement with Fairmount Healthcare Fund II L.P. (the “Stockholder”), pursuant to which the Stockholder agreed to exchange an aggregate of 90,992 shares of Series A Preferred Stock, for an aggregate of 3,639,680 shares of the Company's common stock (the “April 2024 Exchange”). The common stock issued in connection with the April 2024 Exchange was issued without registration under the Securities Act of 1933, as amended (the “Securities Act”) in reliance on the exemption from registration contained in Section 3(a)(9) of the Securities Act. The April 2024 Exchange closed on April 25, 2024, with 346,045 shares of Series A Preferred Stock remaining outstanding following the April 2024 Exchange. On May 14, 2024, the Company's stockholders approved the issuance of its common stock upon conversion of the Company's Series B Preferred Stock to common stock. A total of 254,958 shares of Series B Preferred Stock automatically converted to 10,198,320 shares of common stock; 16,667 shares of Series B Preferred Stock did not automatically convert and remained outstanding as of December 31, 2025. On September 6, 2024, the Company filed a new shelf registration statement on Form S-3 that was declared effective by the SEC for the potential offering, issuance and sale by the Company of up to $500.0 million of its common stock, preferred stock, debt securities, warrants and/or units consisting of all or some of these securities. Concurrent with the filing of the shelf-registration statement, the Company entered into a sales agreement, dated September 6, 2024, with TD Securities (USA) LLC (“TD Cowen”) ("Sales Agreement"), as its sales agent, pursuant to which the Company may issue and sell shares of its common stock for an aggregate offering price of up to $200.0 million under an at-the-market (“ATM”) offering program included in the shelf registration. During the year ended December 31, 2024, the Company sold an aggregate of 777,432 shares of common stock under the ATM resulting in aggregate net proceeds of approximately $20.5 million after deducting commissions paid to TD Cowen as sales agent and other offering costs. On November 18, 2024, the Company entered into an underwriting agreement (the "November 2024 Underwriting Agreement") with Jefferies LLC, Goldman Sachs & Co. LLC, Evercore Group L.L.C. and Guggenheim Securities, LLC as representatives of the several underwriters (collectively, the "November 2024 Underwriters"), pursuant to which the Company sold an aggregate of 8,366,250 shares of its common stock, inclusive of 1,091,250 shares pursuant to the full exercise of the November 2024 Underwriters' over-allotment option, at a public offering price per share of $27.50, resulting in net proceeds of approximately $215.9 million after deducting approximately $14.2 million of underwriting discounts and other offering costs (the "November 2024 Offering"). The November 2024 Offering closed on November 20, 2024 and the over-allotment option was exercised in full on November 26, 2024 and closed on November 29, 2024. In February 2025, the Company filed a new shelf registration statement on Form S-3 (the "February 2025 Shelf Registration Statement") that was declared effective by the SEC for the potential offering, issuance and sale of up to $500.0 million of shares of common stock, preferred stock, debt securities, warrants and/or units consisting of all or some of these securities. Concurrent with the effectiveness of the February 2025 Shelf Registration Statement, the offering of unsold securities under a previous shelf registration statement on Form S-3 (File No. 333-281975), which was initially filed with the SEC on September 6, 2024 and became effective on September 18, 2024, was deemed terminated pursuant to Rule 415(a)(6) under the Securities Act. The February 2025 Shelf Registration Statement contains a sales agreement prospectus supplement covering the offering, issuance and sale by the Company of up to $179.1 million of shares of common stock that may be issued and sold under the Sales Agreement in connection with the ATM offering program. During the three and twelve months ended December 31, 2025, the Company sold an aggregate of 445,668 shares of common stock under the ATM offering program at an average price per share of $33.772 resulting in net proceeds of $14.8 million, after deducting sales agent commissions and other offering costs of $0.3 million. As of December 31, 2025, $164.1 million remained available for sale under the Sales Agreement. Subsequent to December 31, 2025 through February 12, 2026 the Company sold an aggregate of 296,396 shares of common stock under the ATM offering program at an average price per share of $33.566 resulting in net proceeds of $9.7 million after deducting sales agent commissions and other offering costs of $0.2 million. On October 13, 2025, the Company entered into an underwriting agreement (the "October 2025 Underwriting Agreement") with Jefferies LLC, TD Securities (USA) LLC, Leerink Partners LLC and Stifel, Nicolaus & Company, Incorporated as representatives of the several underwriters (collectively, the "October 2025 Underwriters"), pursuant to which the Company sold an aggregate of 17,094,594 shares of its common stock, inclusive of 2,229,729 shares pursuant to the full exercise of the October 2025 Underwriters' over-allotment option, at a public offering price per share of $18.50, resulting in net proceeds of approximately $296.4 million after deducting approximately $19.9 million of underwriting discounts and other offering costs (the "October 2025 Offering"). The over-allotment option was exercised in full on October 14, 2025 and the transaction closed on October 15, 2025. Liquidity The Company is a clinical stage biotechnology company with a limited operating history, and due to its significant research and development expenditures, the Company has generated operating losses since its inception and has not generated any revenue from the commercial sale of any products. There can be no assurance that profitable operations will ever be achieved, and, if achieved, whether profitability can be sustained on a continuing basis. Since its inception and through December 31, 2025, the Company has funded its operations by raising an aggregate of approximately $1.6 billion of gross proceeds from the sale and issuance of convertible preferred stock and common stock, pre-funded warrants, the collection of grant proceeds, and the licensing of its product rights for commercialization of pegzilarginase in Europe and certain countries in the Middle East. As of December 31, 2025, Spyre had an accumulated deficit of $1.1 billion, and cash, cash equivalents, and marketable securities of $756.5 million. Based on current operating plans, the Company has sufficient resources to fund operations for at least one year from the issuance date of these financial statements with existing cash, cash equivalents, and marketable securities. The Company will need to secure additional financing in the future to fund additional research and development, and before a commercial drug can be produced, marketed and sold. If the Company is unable to obtain additional financing or generate license or product revenue, the lack of liquidity could have a material adverse effect on the Company. Basis of Presentation The consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States (“U.S. GAAP”) as defined by the Financial Accounting Standards Board (“FASB”) and include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

Novation of Manufacturing Agreements	12 Months Ended
Novation of Manufacturing Agreements	Dec. 31, 2025
Commitments and Contingencies Disclosure [Abstract]
Novation of Manufacturing Agreements	Novation of Manufacturing Agreements Pursuant to a Novation Agreement dated September 19, 2023 (the “Novation Agreement”), by and between the Company, Paragon and WuXi Biologics (Hong Kong) Limited (“WuXi Biologics”), the Company novated (i) a Biologics Master Services Agreement (the “WuXi Biologics MSA”) and (ii) a Cell Line License Agreement (the “Cell Line License Agreement”). Biologics Master Services Agreement In April 2023, Paragon and WuXi Biologics entered into the WuXi Biologics MSA, which was subsequently novated to the Company by Paragon on September 19, 2023 pursuant to the Novation Agreement. The WuXi Biologics MSA was subsequently amended and restated in October 2024. The WuXi Biologics MSA governs certain development activities and GMP manufacturing and testing for the SPY001, SPY002, and SPY003 programs, as well as potential future programs, on a work order basis. Under the WuXi Biologics MSA, the Company is obligated to pay WuXi Biologics a service fee and all non-cancellable obligations in the amount specified in each work order associated with the agreement for the provision of services. The WuXi Biologics MSA terminates on the later of (i) October 14, 2029 or (ii) the completion of services under all work orders executed by the parties prior to October 14, 2029, unless terminated earlier. The term of each work order terminates upon completion of the services under such work order, unless terminated earlier. The Company can terminate the WuXi Biologics MSA or any work order at any time upon 30 days' prior written notice and immediately upon written notice if WuXi Biologics fails to obtain or maintain required material governmental licenses or approvals. The Company can also terminate the WuXi Biologics MSA, or any work order, in the event that any law is enacted that has, or could be reasonably expected to have, a material adverse effect on the Company or any of its products that is the subject of the WuXi Biologics MSA, in each case, as a result of WuXi Biologics providing services under the WuXi Biologics MSA or the Company being a party to the WuXi Biologics MSA. Either party may terminate a work order (i) at any time upon six months prior notice with reasonable cause, provided however that if WuXi Biologics terminates a work order in such manner, no termination or cancellation fees shall be paid by the Company and (ii) immediately for cause upon (a) the other party’s material breach that remains uncured for 30 days after notice of such breach, (b) the other party’s bankruptcy or (c) a force majeure event that prevents performance for a period of at least 90 days. Cell Line License Agreement In April 2023, Paragon and WuXi Biologics entered into the Cell Line License Agreement, which was subsequently novated to the Company by Paragon pursuant to the Novation Agreement. The Cell Line License Agreement was subsequently amended and restated in October 2024. Under the Cell Line License Agreement, the Company received a non-exclusive, worldwide, sublicensable license to certain of WuXi Biologics’s know-how, cell line, biological materials (the “WuXi Biologics Licensed Technology”) and media and feeds to make, have made, use, sell and import certain therapeutic products produced through the use of the cell line licensed by WuXi Biologics under the Cell Line License Agreement (the “WuXi Biologics Licensed Products”). Specifically, the WuXi Biologics Licensed Technology is used in certain manufacturing activities in support of the SPY001, SPY002, and SPY003 programs. In consideration for the license, the Company agreed to pay WuXi Biologics a non-refundable license fee of $0.2 million. Additionally, if the Company manufactures all of its commercial supplies of bulk drug product with a manufacturer other than WuXi Biologics or its affiliates, the Company is required to make royalty payments to WuXi Biologics of less than one percent of global net sales of WuXi Biologics Licensed Products manufactured by a third-party manufacturer (the “Royalty”). If the Company manufactures part of its commercial supplies of the WuXi Biologics Licensed Products with WuXi Biologics or its affiliates, then the Royalty will be reduced accordingly on a pro rata basis. Subject to the terms of the Cell Line License Agreement, royalties owed under the Cell Line License Agreement may be bought out on a product-by-product basis for a lump-sum payment. The Cell Line License Agreement will continue indefinitely unless terminated (i) by the Company upon six months prior written notice and our payment of all undisputed amounts due to WuXi Biologics through the effective date of termination, (ii) by WuXi Biologics for a material breach by the Company that remains uncured for 60 days after written notice, (iii) by WuXi Biologics if the Company fails to make a payment and such failure continues for 30 days after receiving notice of such failure, or (iv) by either party upon the other party’s bankruptcy.

Net Loss Per Share - Schedule of Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Numerator
Allocation of losses	$ (155,203)	$ (208,018)	$ (338,790)
Series A Preferred Stock
Numerator
Allocation of losses	$ (27,344)	$ (47,624)	$ (239,158)
Denominator
Weighted-average shares outstanding (in shares)	346,045	374,387	434,612
Weighted average pre-funded warrants outstanding (in shares)		0	0
Number of shares used in per share computation, basic (in shares)	346,045	374,387	434,612
Number of shares used in per share computation, diluted (in shares)	346,045	374,387	434,612
Net loss per share, basic (in dollars per share)	$ (79.02)	$ (127.21)	$ (550.28)
Net loss per share, diluted (in dollars per share)	$ (79.02)	$ (127.21)	$ (550.28)
Series B Preferred Stock
Numerator
Allocation of losses	$ (1,317)	$ (10,839)	$ (4,749)
Denominator
Weighted-average shares outstanding (in shares)	16,667		8,630
Weighted average pre-funded warrants outstanding (in shares)		0	0
Number of shares used in per share computation, basic (in shares)	16,667	85,208	8,630
Number of shares used in per share computation, diluted (in shares)	16,667	85,208	8,630
Net loss per share, basic (in dollars per share)	$ (79.02)	$ (127.21)	$ (550.29)
Net loss per share, diluted (in dollars per share)	$ (79.02)	$ (127.21)	$ (550.29)
Common Stock
Numerator
Allocation of losses	$ (126,541)	$ (149,555)	$ (94,883)
Denominator
Weighted-average shares outstanding (in shares)	64,056,442	46,940,206	6,201,954
Weighted average pre-funded warrants outstanding (in shares)		87,432	695,111
Number of shares used in per share computation, basic (in shares)	64,056,442	47,027,638	6,897,065
Number of shares used in per share computation, diluted (in shares)	64,056,442	47,027,638	6,897,065
Net loss per share, basic (in dollars per share)	$ (1.98)	$ (3.18)	$ (13.76)
Net loss per share, diluted (in dollars per share)	$ (1.98)	$ (3.18)	$ (13.76)

Cash Equivalents and Marketable Securities - Schedule of Available-for-Sale Securities in an Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Fair Value
Less Than 12 Months	$ 180,961	$ 249,264
12 Months or Longer	0	0
Total	180,961	249,264
Unrealized Losses
Less Than 12 Months	(116)	(493)
12 Months or Longer	0	0
Total	(116)	(493)
Commercial paper
Fair Value
Less Than 12 Months	99,837	67,200
12 Months or Longer	0	0
Total	99,837	67,200
Unrealized Losses
Less Than 12 Months	(80)	(77)
12 Months or Longer	0	0
Total	(80)	(77)
Corporate bonds
Fair Value
Less Than 12 Months	58,296	42,916
12 Months or Longer	0	0
Total	58,296	42,916
Unrealized Losses
Less Than 12 Months	(23)	(48)
12 Months or Longer	0	0
Total	(23)	(48)
U.S. government treasury securities
Fair Value
Less Than 12 Months		126,588
12 Months or Longer		0
Total		126,588
Unrealized Losses
Less Than 12 Months		(296)
12 Months or Longer		0
Total		(296)
U.S. government agency securities
Fair Value
Less Than 12 Months	22,828	12,560
12 Months or Longer	0	0
Total	22,828	12,560
Unrealized Losses
Less Than 12 Months	(13)	(72)
12 Months or Longer	0	0
Total	$ (13)	$ (72)

Related Party Transactions (Tables)

12 Months Ended

Dec. 31, 2025

Schedule of Expenses related to Related Party which were Settled in Cash

The following is the summary of expenses related to the Paragon Agreement and License Agreements, which are ultimately settled in cash (in millions) and recorded within Research and development in the consolidated statement of operations for the periods presented:


	Year Ended December 31,
	2025		2024		2023
Reimbursable costs under the Paragon Agreement	$	0.1	$	15.3	$	37.1
License Agreements milestone and sublicensing fees	10.4		10.2		—
Total related party expense (excludes stock comp)	$	10.5	$	25.5	$	37.1

The following is the summary of Related party accounts payable and other current liabilities (in millions):


	December 31,
	2025		2024
Reimbursable costs under the Paragon Agreement	$	—	$	0.1
License Agreements development milestone liability (see Note 9)	—		0.5
Total related party accounts payable	$	—	$	0.6

Related Party Transactions - Narrative (Details)			1 Months Ended	12 Months Ended
Related Party Transactions - Narrative (Details)	Nov. 22, 2023 installment $ / shares shares	Jun. 22, 2023 USD ($)	May 31, 2023 USD ($)	Dec. 31, 2025 USD ($) seat shares	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Mar. 31, 2024
Related Party Transaction [Line Items]
Stock-based compensation				$ 37,614,000	$ 44,833,000	$ 25,675,000
Options granted (in shares) \| shares				2,623,217
Private Placement
Related Party Transaction [Line Items]
Proceeds from issuance of private placement, net				$ 180,000,000.0
Parapyre Option Obligation
Related Party Transaction [Line Items]
Stock-based compensation				0
Related Party
Related Party Transaction [Line Items]
Development cost reduction percentage							50.00%
Stock-based compensation				1,000,000.0	15,600,000	11,500,000
Related Party \| Parapyre Option Obligation
Related Party Transaction [Line Items]
Stock-based compensation				0	14,500,000	11,400,000
Paragon Agreement
Related Party Transaction [Line Items]
Related party expenses incurred prior to asset acquisition		$ 19,000,000.0
Related party expenses unpaid prior to asset acquisition		19,000,000.0
Paragon Agreement \| Related Party
Related Party Transaction [Line Items]
Research initiation fees		3,000,000.0	$ 3,000,000.0
Reimbursable research costs		$ 16,000,000.0
Amount of related party transaction				$ 200,000	31,800,000	39,500,000
Reduction in research and development expense					5,900,000
Common stock, shares outstanding, percentage available to purchase on a diluted basis				1.00%
Appoint of Board Members
Related Party Transaction [Line Items]
Number of board seats held by related party \| seat				2
Paragon Agreement, Subsequent to Asset Acquisition \| Related Party
Related Party Transaction [Line Items]
Amount of related party transaction				$ 100,000	29,800,000	48,500,000
Sale of Stock, December 2023 PIPE \| Related Party
Related Party Transaction [Line Items]
Proceeds from issuance of private placement, net				10,000,000.0
Consulting Agreement \| Related Party
Related Party Transaction [Line Items]
Options granted (in shares) \| shares	477,000
Exercise price (in dollars per share) \| $ / shares	$ 10.39
Number of monthly installments \| installment	48
Stock-based compensation expense				$ 1,000,000.0	$ 1,100,000	$ 100,000
Consulting Agreement \| Related Party \| Share-Based Payment Arrangement, Tranche One
Related Party Transaction [Line Items]
Vesting percentage	25.00%
Awards granted, vesting period	1 year
Paragon Therapeutics Inc \| Maximum \| Paragon Agreement \| Related Party
Related Party Transaction [Line Items]
Percentage of ownership by noncontrolling owner				5.00%
Fairmount Funds Management LLC \| Minimum \| Paragon Agreement \| Related Party
Related Party Transaction [Line Items]
Percentage of ownership by noncontrolling owner				5.00%
Percentage of ownership held in third party				5.00%

Consolidated Statements of Operations - USD ($)

12 Months Ended

Dec. 31, 2025

Dec. 31, 2024

Dec. 31, 2023

Revenue:

Total revenue

$ 0

$ 886,000

Operating expenses:

Research and development

^[1]

171,653,000

162,790,000

89,504,000

General and administrative

^[2]

47,909,000

45,776,000

39,946,000

Acquired in-process research and development

130,188,000

Gain on sale of in-process research and development asset

(10,000,000)

(16,449,000)

Total operating expenses

209,562,000

208,566,000

243,189,000

Loss from operations

(209,562,000)

(208,566,000)

(242,303,000)

Other income (expense):

Interest income

24,885,000

21,312,000

6,147,000

Other income (expense), net

29,459,000

(20,713,000)

(19,130,000)

Total other income (expense)

54,344,000

599,000

(96,513,000)

Loss before income tax expense

(155,218,000)

(207,967,000)

(338,816,000)

Income tax benefit (expense)

15,000

(51,000)

26,000

Net loss

(155,203,000)

(208,018,000)

(338,790,000)

Forward Contract Liability

Other income (expense):

Change in fair value of forward contract liability

(83,530,000)

Series A Non-Voting Convertible Preferred Stock

Other income (expense):

Net loss

$ (27,344,000)

$ (47,624,000)

$ (239,158,000)

Net loss per share, basic (in dollars per share)

$ (79.02)

$ (127.21)

$ (550.28)

Net loss per share, diluted (in dollars per share)

$ (79.02)

$ (127.21)

$ (550.28)

Weighted-average common shares outstanding, basic (in shares)

346,045

374,387

434,612

Weighted-average common shares outstanding, diluted (in shares)

346,045

374,387

434,612

Series B Non-Voting Convertible Preferred Stock

Other income (expense):

Net loss

$ (1,317,000)

$ (10,839,000)

$ (4,749,000)

Net loss per share, basic (in dollars per share)

$ (79.02)

$ (127.21)

$ (550.29)

Net loss per share, diluted (in dollars per share)

$ (79.02)

$ (127.21)

$ (550.29)

Weighted-average common shares outstanding, basic (in shares)

16,667

85,208

8,630

Weighted-average common shares outstanding, diluted (in shares)

16,667

85,208

8,630

Common Stock

Other income (expense):

Net loss

$ (126,541,000)

$ (149,555,000)

$ (94,883,000)

Net loss per share, basic (in dollars per share)

$ (1.98)

$ (3.18)

$ (13.76)

Net loss per share, diluted (in dollars per share)

$ (1.98)

$ (3.18)

$ (13.76)

Weighted-average common shares outstanding, basic (in shares)

64,056,442

47,027,638

6,897,065

Weighted-average common shares outstanding, diluted (in shares)

64,056,442

47,027,638

6,897,065

Development fee and royalty

Revenue:

Total revenue

$ 0

$ 886,000

[1]	Includes $10.5 million, $40.1 million and $48.5 million in related party expenses for the years ended December 31, 2025, 2024 and 2023, respectively.
[2]	Includes $1.0 million, $1.1 million and $0.1 million in related party expenses for the years ended December 31, 2025, 2024 and 2023, respectively.

Cybersecurity Risk Management and Strategy Disclosure	12 Months Ended
Cybersecurity Risk Management and Strategy Disclosure	Dec. 31, 2025
Cybersecurity Risk Management, Strategy, and Governance [Line Items]
Cybersecurity Risk Management Processes for Assessing, Identifying, and Managing Threats [Text Block]	In the ordinary course of business, we collect, use, store, and transmit digitally confidential, sensitive, proprietary, personal, and health-related information. The secure maintenance of this information and our information technology systems is important to our operations and business strategy. To this end, we have implemented processes using the cybersecurity risk framework published by the NIST designed to assess, identify, and manage risks from potential unauthorized occurrences on or through our information technology systems that may result in adverse effects on the confidentiality, integrity, and availability of these systems and the data residing therein. These processes are managed and monitored by a dedicated information technology team, which is led by our Vice President, Information Technology ("IT"), and include mechanisms, controls, technologies, systems, and other processes designed to prevent or mitigate data loss, theft, misuse, or other security incidents or vulnerabilities affecting the data and maintain a stable information technology environment. Our cybersecurity risk management processes also incorporate the use of automated and data-driven tools provided by third-party vendors to support threat detection, monitoring, and incident response, and are designed to address evolving cybersecurity threats, including those that may be enabled by artificial intelligence. Specific measures include regular penetration and vulnerability testing, data recovery testing, security audits, and ongoing risk assessments. We conduct due diligence on and audits of key technology vendors, contract research organizations (CROs), and other third-party contractors and suppliers. Additionally, we conduct employee training that covers identifying threats (phishing, social engineering), secure practices (strong passwords, multi-factor authentication, safe internet use, data handling), and incident response (reporting procedures), turning employees into the first line of defense through regular, engaging education on topics like malware, remote work security, physical security, cloud security, mobile devices, and social media risks. We also regularly consult with outside advisors and experts. Their assistance helps us assess, identify, and manage cybersecurity risks, anticipate future threats and trends, and understand their potential impact on our risk environment.
Cybersecurity Risk Management Processes Integrated [Flag]	true
Cybersecurity Risk Management Processes Integrated [Text Block]	The secure maintenance of this information and our information technology systems is important to our operations and business strategy. To this end, we have implemented processes using the cybersecurity risk framework published by the NIST designed to assess, identify, and manage risks from potential unauthorized occurrences on or through our information technology systems that may result in adverse effects on the confidentiality, integrity, and availability of these systems and the data residing therein.
Cybersecurity Risk Management Third Party Engaged [Flag]	true
Cybersecurity Risk Third Party Oversight and Identification Processes [Flag]	true
Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Flag]	false
Cybersecurity Risk Board of Directors Oversight [Text Block]	The Board of Directors, as a whole and at the committee level, has oversight for the most significant risks facing us and for our processes to identify, prioritize, assess, manage, and mitigate those risks.
Cybersecurity Risk Board Committee or Subcommittee Responsible for Oversight [Text Block]	The Audit Committee, which is comprised solely of independent directors, has been designated by our Board to oversee cybersecurity risks.
Cybersecurity Risk Process for Informing Board Committee or Subcommittee Responsible for Oversight [Text Block]	The Audit Committee receives regular updates on cybersecurity and information technology matters and related risk exposures from our Vice President, IT, as well as other members of the senior leadership team. The Board also receives updates from management and the Audit Committee on cybersecurity risks on at least an annual basis.
Cybersecurity Risk Role of Management [Text Block]	To this end, we have implemented processes using the cybersecurity risk framework published by the NIST designed to assess, identify, and manage risks from potential unauthorized occurrences on or through our information technology systems that may result in adverse effects on the confidentiality, integrity, and availability of these systems and the data residing therein. These processes are managed and monitored by a dedicated information technology team, which is led by our Vice President, Information Technology ("IT"), and include mechanisms, controls, technologies, systems, and other processes designed to prevent or mitigate data loss, theft, misuse, or other security incidents or vulnerabilities affecting the data and maintain a stable information technology environment.
Cybersecurity Risk Management Positions or Committees Responsible [Flag]	true
Cybersecurity Risk Management Positions or Committees Responsible [Text Block]	Our Vice President, IT, who reports directly to our Chief Financial Officer, has over 26 years of experience managing information technology and cybersecurity matters and is certified as a Certified Information Systems Security Professional. Together with other members of our senior leadership team, our Vice President, IT is responsible for assessing and managing cybersecurity risks.
Cybersecurity Risk Management Expertise of Management Responsible [Text Block]	Our Vice President, IT, who reports directly to our Chief Financial Officer, has over 26 years of experience managing information technology and cybersecurity matters and is certified as a Certified Information Systems Security Professional.
Cybersecurity Risk Process for Informing Management or Committees Responsible [Text Block]	The Audit Committee receives regular updates on cybersecurity and information technology matters and related risk exposures from our Vice President, IT, as well as other members of the senior leadership team. The Board also receives updates from management and the Audit Committee on cybersecurity risks on at least an annual basis.
Cybersecurity Risk Management Positions or Committees Responsible Report to Board [Flag]	true

Leases (Tables)

12 Months Ended

Dec. 31, 2025

Leases [Abstract]

Schedule of Lease Cost

The following table summarizes the lease costs pertaining to the Company’s operating leases (in thousands):


	Year Ended December 31,
	2025		2024		2023
Operating lease cost	$	—	$	—	$	455
Variable lease cost	—		—		471
Total lease cost	$	—	$	—	$	926

Restructuring Charges - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
	Jun. 30, 2023	Jun. 30, 2023	Jun. 30, 2023	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Aug. 31, 2023
Restructuring Cost and Reserve [Line Items]
Employee workforce, termination percentage			83.00%
Cash severance payments and other employee-related costs						$ 6,400
Cash payments for employee related restructuring charges						5,300
Non-cash stock-based compensation expense related to accelerated vesting of stock-based awards						$ 1,000
Restructuring Charges, Statement of Income or Comprehensive Income [Extensible Enumeration]						Research and development
Total consideration from disposal of long lived assets	$ 500	$ 500	$ 500
Loss on disposal of long-lived assets				$ 0	$ 0	$ 915
Lease asset impairment	900
Impairment on leasehold improvements	$ 1,700
Termination fee amount							$ 2,000
Research and Development Expense
Restructuring Cost and Reserve [Line Items]
Loss on disposal of long-lived assets		700
General and Administrative Expense
Restructuring Cost and Reserve [Line Items]
Loss on disposal of long-lived assets		$ 200

Summary of Significant Accounting Policies - Schedule of Useful Lives of Property and Equipment (Details)	Dec. 31, 2025
Laboratory equipment
Property Plant And Equipment [Line Items]
Useful lives of the property and equipment	5 years
Furniture and office equipment
Property Plant And Equipment [Line Items]
Useful lives of the property and equipment	5 years
Computer equipment
Property Plant And Equipment [Line Items]
Useful lives of the property and equipment	3 years
Software
Property Plant And Equipment [Line Items]
Useful lives of the property and equipment	3 years

Stock-Based Compensation - Schedule of Employee and Non-Employee Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Shares Issuable Under Options
Outstanding, beginning balance (in shares)	9,253,158
Granted (in shares)	2,623,217
Exercised (in shares)	(307,673)
Forfeited (in shares)	(198,455)
Outstanding, ending balance (in shares)	11,370,247	9,253,158
Options vested and expected to vest (in shares)	11,370,247
Options exercisable (in shares)	5,164,959
Weighted Average Exercise Price
Outstanding, beginning balance (in dollars per share)	$ 15.08
Granted (in dollars per share)	19.98
Exercised (in dollars per share)	8.68
Forfeited (in dollars per share)	33.38
Outstanding, ending balance (in dollars per share)	16.06	$ 15.08
Options vested and expected to vest (in dollars per share)	16.06
Options exercisable (in dollars per share)	$ 14.50
Weighted Average Remaining Contractual Term
Outstanding	8 years 1 month 28 days	8 years 9 months 18 days
Options vested and expected to vest	8 years 1 month 28 days
Options exercisable	7 years 11 months 12 days
Aggregate Intrinsic Value
Outstanding	$ 191,198	$ 90,016
Options vested and expected to vest	191,198
Options exercisable	$ 95,153

Consolidated Statements of Changes in Convertible Preferred Stock and Stockholders’ Equity - USD ($) $ in Thousands	Total	Series A Non-Voting Convertible Preferred Stock	Series B Non-Voting Convertible Preferred Stock	Common Stock	Preferred Stock Series A Non-Voting Convertible Preferred Stock	Preferred Stock Series B Non-Voting Convertible Preferred Stock	Common Stock	Common Stock Series A Non-Voting Convertible Preferred Stock	Common Stock Common Stock	Additional Paid-in Capital	Additional Paid-in Capital Series A Non-Voting Convertible Preferred Stock	Additional Paid-in Capital Common Stock	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2022						0
Beginning balance at Dec. 31, 2022						$ 0
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of Series B non-voting convertible preferred stock in connection with private placement, net of financing costs (in shares)						150,000
Issuance of Series B non-voting convertible preferred stock in connection with private placement, net of financing costs						$ 84,555
Ending balance (in shares) at Dec. 31, 2023						150,000
Ending balance at Dec. 31, 2023						$ 84,555
Beginning balance (in shares) at Dec. 31, 2022					0	0
Beginning balance (in shares) at Dec. 31, 2022							2,614,000
Beginning balance at Dec. 31, 2022	$ 50,305				$ 0	$ 0	$ 6			$ 475,971			$ (48)	$ (425,624)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock in connection with private placement, net of financing costs (in shares)					721,000				6,000,000
Issuance of stock in connection with private placement, net of financing costs		$ 197,364		$ 84,555	$ 197,364							$ 84,555
Issuance of Series A non-voting convertible preferred stock in connection with the asset acquisition of Spyre and settlement of related forward contract (in shares)					365,000
Issuance of Series A non-voting convertible preferred stock in connection with the asset acquisition of Spyre and settlement of related forward contract		189,741			$ 189,741
Conversion of non-voting convertible preferred stock into common stock (in shares)					(649,000)			25,972,000
Conversion of non-voting convertible preferred stock into common stock		0			$ (202,178)			$ 3			$ 202,175
Issuance of common stock in connection with the asset acquisition of Spyre (in shares)							518,000
Issuance of common stock in connection with the asset acquisition of Spyre	3,768						$ 1			3,767
Issuance of common stock in connection with exercise of pre-funded warrants (in shares)							905,000
Issuance of common stock in connection with exercise of stock options and employee stock purchase plan (in shares)							48,000
Issuance of common stock in connection with exercise of stock options and employee stock purchase plan	405									405
CVR distribution to common stockholders	(29,500)									(29,500)
Stock-based compensation expense	14,347									14,347
Issuance of Parapyre Option Obligation warrants	11,471									11,471
Foreign currency translation adjustment	37												37
Unrealized gain (loss) on marketable securities	313												313
Net loss	(338,790)	$ (239,158)	$ (4,749)	(94,883)										(338,790)
Ending balance (in shares) at Dec. 31, 2023		437,037			437,000	0
Ending balance (in shares) at Dec. 31, 2023							36,057,000
Ending balance at Dec. 31, 2023	184,016				$ 184,927	$ 0	$ 10			763,191			302	(764,414)
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of Series B non-voting convertible preferred stock in connection with private placement, net of financing costs (in shares)						122,000
Issuance of Series B non-voting convertible preferred stock in connection with private placement, net of financing costs						$ 168,850
Stockholder approval of the issuance of common stock upon conversion of Series B convertible non-voting preferred stock (in shares)						(272,000)
Stockholder approval of the issuance of common stock upon conversion of Series B convertible non-voting preferred stock						$ (253,405)
Ending balance (in shares) at Dec. 31, 2024						0
Ending balance at Dec. 31, 2024						$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of non-voting convertible preferred stock into common stock (in shares)						(255,000)	10,198,000
Conversion of non-voting convertible preferred stock into common stock	0					$ (244,010)	$ 1			244,009
Issuance of common stock in connection with exercise of pre-funded warrants (in shares)							250,000
Issuance of common stock in connection with exercise of pre-funded warrants	1									1
Issuance of common stock in connection with exercise of stock options and employee stock purchase plan (in shares)							931,000
Issuance of common stock in connection with exercise of stock options and employee stock purchase plan	7,511									7,511
CVR distribution to common stockholders (in shares)							38,000
Stock-based compensation expense	30,374									30,374
Issuance of Parapyre Option Obligation warrants	14,459									14,459
Foreign currency translation adjustment	4												4
Unrealized gain (loss) on marketable securities	(126)												(126)
Stockholder approval of the issuance of common stock upon conversion of Series B convertible non-voting preferred stock (in shares)						272,000
Stockholder approval of the issuance of common stock upon conversion of Series B convertible non-voting preferred stock	253,405					$ 253,405
Exchange of Series A non-voting convertible preferred stock for common stock (in shares)					(91,000)		3,640,000
Exchange of Series A non-voting convertible preferred stock for common stock	0				$ (38,502)		$ 1			38,501
Issuance of common stock in connection with at-the-market offering program, net of financing costs (in shares)							777,000
Issuance of common stock in connection with at-the-market offering program, net of financing costs	20,504									20,504
Issuance of common stock in connection with follow-on offering, net of financing costs (in shares)							8,366,000
Issuance of common stock in connection with follow-on offering, net of financing costs	215,674						$ 1			215,673
Net loss	$ (208,018)	$ (47,624)	$ (10,839)	(149,555)										(208,018)
Ending balance (in shares) at Dec. 31, 2024		346,045	16,667		346,000	17,000
Ending balance (in shares) at Dec. 31, 2024	60,257,023						60,257,000
Ending balance at Dec. 31, 2024	$ 517,804				$ 146,425	$ 9,395	$ 13			1,334,223			180	(972,432)
Ending balance (in shares) at Dec. 31, 2025						0
Ending balance at Dec. 31, 2025						$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with exercise of stock options and employee stock purchase plan (in shares)							354,000
Issuance of common stock in connection with exercise of stock options and employee stock purchase plan	3,306									3,306
Stock-based compensation expense	37,614									37,614
Foreign currency translation adjustment	(22)												(22)
Unrealized gain (loss) on marketable securities	711												711
Issuance of common stock in connection with at-the-market offering program, net of financing costs (in shares)							446,000
Issuance of common stock in connection with at-the-market offering program, net of financing costs	14,745									14,745
Issuance of common stock in connection with follow-on offering, net of financing costs (in shares)							17,095,000
Issuance of common stock in connection with follow-on offering, net of financing costs	296,281						$ 2			296,279
Vesting of restricted stock units (in shares)							38,000
Net loss	$ (155,203)	$ (27,344)	$ (1,317)	$ (126,541)										(155,203)
Ending balance (in shares) at Dec. 31, 2025		346,045	16,667		346,000	17,000
Ending balance (in shares) at Dec. 31, 2025	78,189,811						78,190,000
Ending balance at Dec. 31, 2025	$ 715,236				$ 146,425	$ 9,395	$ 15			$ 1,686,167			$ 869	$ (1,127,635)

Cash Equivalents and Marketable Securities - Schedule of Estimated Fair Value of Cash Equivalents and Marketable Securities and the Gross Unrealized Gains and Losses (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Cash equivalents:
Amortized Cost	$ 83,991	$ 87,734
Gross Unrealized Gains	0	6
Gross Unrealized Losses	0	0
Estimated Fair Value	83,991	87,740
Marketable securities:
Amortized Cost	669,942	513,507
Gross Unrealized Gains	986	651
Gross Unrealized Losses	(116)	(493)
Estimated Fair Value	670,812	513,665
Money market funds
Cash equivalents:
Amortized Cost	74,004	65,902
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	74,004	65,902
Commercial paper
Cash equivalents:
Amortized Cost	9,987	21,832
Gross Unrealized Gains	0	6
Gross Unrealized Losses	0	0
Estimated Fair Value	9,987	21,838
U.S. government treasury securities
Cash equivalents:
Amortized Cost		0
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Estimated Fair Value		0
Commercial paper
Marketable securities:
Amortized Cost	184,423	143,265
Gross Unrealized Gains	25	104
Gross Unrealized Losses	(80)	(77)
Estimated Fair Value	184,368	143,292
Corporate bonds
Marketable securities:
Amortized Cost	100,753	56,471
Gross Unrealized Gains	60	25
Gross Unrealized Losses	(23)	(48)
Estimated Fair Value	100,790	56,448
U.S. government treasury securities
Marketable securities:
Amortized Cost	265,316	227,155
Gross Unrealized Gains	748	385
Gross Unrealized Losses	0	(296)
Estimated Fair Value	266,064	227,244
U.S. government agency securities
Marketable securities:
Amortized Cost	119,450	86,616
Gross Unrealized Gains	153	137
Gross Unrealized Losses	(13)	(72)
Estimated Fair Value	$ 119,590	$ 86,681

Licensing Agreements	12 Months Ended
Licensing Agreements	Dec. 31, 2025
Licensing Agreements [Abstract]
Licensing Agreements	Licensing Agreements On July 12, 2023, December 14, 2023, and June 5, 2024, the Company exercised the Option available under the Paragon Agreement with respect to the SPY001, SPY002, and SPY003 research programs, respectively. On May 14, 2024, the Company and Paragon entered into (i) a license agreement (the “SPY001 License Agreement”), pursuant to which Paragon granted the Company a royalty-bearing, world-wide, exclusive license to develop, manufacture, commercialize or otherwise exploit certain antibodies and products targeting α4ß7 integrin and (ii) a license agreement (the “SPY002 License Agreement”), pursuant to which Paragon granted the Company a royalty-bearing, world-wide, exclusive license to develop, manufacture, commercialize or otherwise exploit certain antibodies and products targeting TL1A, respectively. On October 11, 2024, the Company and Paragon entered into a license agreement (the "SPY003 License Agreement" and, together with the SPY001 License Agreement and the SPY002 License Agreement, the "License Agreements"), pursuant to which Paragon granted the Company a royalty-bearing, world-wide, exclusive license to develop, manufacture, commercialize or otherwise exploit certain antibodies and products targeting IL-23 in the field of IBD. On February 24, 2025, the SPY003 License Agreement was amended and restated to, among other things, clarify each party's rights and obligations with respect to license exclusivity and patent prosecution and correct certain clerical errors. Under the terms of each License Agreement, the Company is obligated to pay Paragon up to $22.0 million based on specific development, regulatory and clinical milestones for the first product under each agreement, respectively, that achieves such specified milestones, including a milestone payment of $3.0 million upon the first dosing of a human patient in a Phase 2 trial. In addition, the following summarizes other key terms of each License Agreement: •Paragon will provide the Company with an exclusive license (such license, with respect to the SPY003 License Agreement only, being limited to the field of IBD) to its patents covering the related antibody, the method of use and its method of manufacture. •Paragon will not conduct any new campaigns that generate anti-α4ß7 or anti-TL1A monospecific antibodies in any field or anti-IL-23 monospecific antibodies in the field of IBD, in each case for at least 5 years. •The Company will pay Paragon a low single-digit percentage royalty for single antibody products and a mid single-digit percentage royalty for products containing more than one antibody from Paragon. •There is a royalty step-down of 1/3rd if there is no Paragon patent in effect during the royalty term. •The royalty term ends on the later of (i) the last-to-expire licensed patent or Company patent directed to the manufacture, use or sale of a licensed antibody in the country at issue or (ii) 12 years from the date of first sale of a Company product. •Agreement may be terminated on 60 days’ notice by the Company; on material breach without cure; and to the extent permitted by law, on a party’s insolvency or bankruptcy. •With respect to the SPY002 License Agreement only, on a product by product basis, the Company will pay sublicensing fees of up to approximately $20.0 million upon the achievement of mostly commercial milestones. The Company recognizes the expense associated with each milestone when the achievement of the milestone is deemed probable. During the years ended December 31, 2025 and 2024, the Company recognized expense of $8.5 million and $9.5 million, respectively, related to Paragon license milestone payments recorded within Research and development expenses in the accompanying condensed statement of operations. There was no such expense for the year ended December 31, 2023. For the years ended December 31, 2025 and 2024, the Company made cash milestone payments to Paragon totaling $8.5 million and $9.5 million. There were no such payments for the year ended December 31, 2023. As of December 31, 2025 and 2024, there were no Paragon license milestone payments outstanding and payable to Paragon. Additionally, the Company recognized $1.9 million and $0.7 million related to sublicensing fees and which was recorded as Research and development expenses in the accompanying statement of operations for the year ended December 31, 2025 and 2024, respectively. There was no such expense for the year ended December 31, 2023. For the year ended December 31, 2025 and 2024, the Company made sublicensing fees payments to Paragon totaling $2.4 million and $0.2 million. There were no such payments for the year ended December 31, 2023. As of December 31, 2025 and 2024, nil and $0.5 million in sublicensing fees were outstanding and payable to Paragon, respectively.

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2025	Dec. 31, 2024
Convertible preferred stock, par value (in dollars per share)	$ 0.0001
Convertible preferred stock, authorized (in shares)	10,000,000
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, authorized (in shares)	400,000,000	400,000,000
Common stock, issued (in shares)	78,189,811	60,257,023
Common stock, outstanding (in shares)	78,189,811	60,257,023
Series A Non-Voting Convertible Preferred Stock
Convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Convertible preferred stock, authorized (in shares)	1,086,341	1,086,341
Convertible preferred stock, issued (in shares)	346,045	346,045
Convertible preferred stock, outstanding (in shares)	346,045	346,045
Series B Non-Voting Convertible Preferred Stock
Convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Convertible preferred stock, authorized (in shares)	271,625	271,625
Convertible preferred stock, issued (in shares)	16,667	16,667
Convertible preferred stock, outstanding (in shares)	16,667	16,667
Preferred Stock, Excluding Non-Voting Stock
Convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Convertible preferred stock, authorized (in shares)	8,642,034	8,642,034
Convertible preferred stock, issued (in shares)	0	0
Convertible preferred stock, outstanding (in shares)	0	0

Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2025

Fair Value Disclosures [Abstract]

Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis

The following tables set forth the fair value of the Company’s financial assets and liabilities at fair value on a recurring basis based on the three-tier fair value hierarchy (in thousands):


	December 31, 2025
	Level 1		Level 2		Level 3		Total
Financial Assets
Money market funds	$	74,004	$	—	$	—	$	74,004
U.S. government treasury securities	266,064		—		—		266,064
U.S. government agency securities	—		119,590		—		119,590
Commercial paper	—		194,355		—		194,355
Corporate bonds	—		100,790		—		100,790
Total financial assets	$	340,068	$	414,735	$	—	$	754,803

Liabilities:
CVR liability	$	—	$	—	$	26,680	$	26,680
Total liabilities	$	—	$	—	$	26,680	$	26,680


	December 31, 2024
	Level 1		Level 2		Level 3		Total
Financial Assets
Money market funds	$	65,902	$	—	$	—	$	65,902
U.S. government treasury securities	227,244		—		—		227,244
U.S. government agency securities	—		86,681		—		86,681
Commercial paper	—		165,130		—		165,130
Corporate bonds	—		56,448		—		56,448
Total financial assets	$	293,146	$	308,259	$	—	$	601,405

Liabilities:
CVR liability	$	—	$	—	$	61,700	$	61,700
Total liabilities	$	—	$	—	$	61,700	$	61,700

Schedule of Changes in Derivative Liabilities

The following table presents changes in the forward contract liability for the periods presented (in millions):


	Forward Contract Liability
Beginning balance as of June 22, 2023	$	106.2
Change in fair value	83.5
Issuance of Series A Preferred Stock on July 7, 2023	(189.7)
Ending balance as of December 31, 2023	$	—

The following table presents changes in the CVR liability for the periods presented (in thousands):


	CVR Liability
Beginning balance as of December 31, 2024	$	61,700

Changes in the fair value of the CVR liability	(29,769)
Payments	(5,251)
Ending Balance as of December 31, 2025	$	26,680

Schedule of Significant Inputs used to Estimate the Fair Value of Derivative Liabilities

The significant inputs used to estimate the fair value of the CVR liability were as follows:


			December 31, 2025
Estimated cash flow dates			05/15/26 - 08/15/29
Estimated probability of success			0% - 72%
Estimated reimbursement rate compared to reimbursement target			45% - 55%
Risk-adjusted discount rates			9.85% - 9.97%

Property and Equipment, Net	12 Months Ended
Property and Equipment, Net	Dec. 31, 2025
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net The Company did not have any property, plant, and equipment assets as of December 31, 2025 and 2024. Depreciation and amortization expense for the years ended December 31, 2023 was $0.7 million. There was no depreciation and amortization expense for the year ended December 31, 2025 and 2024. All of the Company’s long-lived assets were located in the United States. Sale of Assets On April 12, 2023, based on the review of the inconclusive interim results from the Company's Phase 1/2 clinical trial of pegtarviliase for the treatment of classical homocystinuria and other business considerations, the Company announced that it had initiated a process to explore strategic alternatives to maximize stockholder value and engaged an independent exclusive financial advisor to support this process. As a result, the Company implemented a restructuring plan resulting in an approximate 83% reduction of the Company’s existing headcount by June 30, 2023. During the second quarter of 2023, the Company sold various lab equipment, consumables, and furniture and fixtures for total consideration of $0.5 million. After recording the disposal of all the Company's property and equipment net of proceeds, the Company recorded a $0.7 million and $0.2 million loss on disposal of long-lived assets which is included in Research and development and General and administrative expenses, respectively.

Paragon Agreement	12 Months Ended
Paragon Agreement	Dec. 31, 2025
Related Party Transactions [Abstract]
Paragon Agreement	Paragon Agreement In May 2023, Pre-Merger Spyre entered into the original Paragon Agreement with Paragon and Parapyre Holding LLC ("Parapyre"), which was subsequently amended and restated on September 29, 2023 and May 14, 2024. Pursuant to the Paragon Agreement, the Option provided for the right to acquire the intellectual property rights related to four research programs from Paragon in accordance with a license agreement to be entered into following each exercise of the Option. Under the Paragon Agreement, the terms of such license agreement would be consistent with the economics and other terms set out in the Paragon Agreement and, in the event of failure to reach an agreement on the definitive terms, the matter would be resolved via arbitration. In consideration for the Option granted under the Paragon Agreement, Pre-Merger Spyre was obligated to pay Paragon an upfront cash amount of $3.0 million in research initiation fees. In addition, Pre-Merger Spyre was obligated to compensate Paragon on a quarterly basis for its services performed under each research program based on the actual costs incurred with mark-up costs pursuant to the terms of the Paragon Agreement. As of the date of the Asset Acquisition, Pre-Merger Spyre had incurred total expenses of $19.0 million under the Paragon Agreement since inception, which included the $3.0 million research initiation fee and $16.0 million of historical reimbursable expenses owed to Paragon. As of June 22, 2023, $19.0 million was unpaid and was assumed by the Company through the Asset Acquisition. Furthermore, the Paragon Agreement provided for an annual equity grant of options to purchase 1% of the then outstanding shares of Spyre’s common stock, on a fully diluted basis, on the last business day of each calendar year, during the term of the Paragon Agreement, at the fair market value determined by the board of directors of Spyre (the "Parapyre Option Obligation"). As a result of the Asset Acquisition, the Company assumed the rights and obligations of Pre-Merger Spyre under the Paragon Agreement, including the Parapyre Option Obligation. Pursuant to the Paragon Agreement, on a research program-by-research program basis following the finalization of the research plan for each respective research program, the Company is required to pay Paragon a nonrefundable fee in cash of $0.8 million. In September 2023, the Company amended the Paragon Agreement to amend and restate certain terms of the option grant pertaining to the Parapyre Option Obligation, including but not limited to (i) defining that the annual equity grant of warrants is based on the outstanding shares of the Company’s common stock on a fully-diluted basis, (ii) establishing the grant date as the last business day of 2023 and 2024, and (iii) defining the term of the warrants granted as ten years. In May 2024, the Company, Paragon and Parapyre entered into a second amended and restated antibody discovery and option agreement that amends and restates that certain amended and restated antibody discovery and option agreement, dated September 29, 2023, by and between Paragon, Parapyre and Spyre Therapeutics, LLC, in order to, among other things, (i) replace the Company’s subsidiary with the Company as a party to the agreement and (ii) amend certain terms related to the SPY003 research program, including without limitation, (a) establishing an SPY003 antibody selection process pursuant to which the Company and Paragon shall alternate in turn to select a project antibody to be included and excluded, respectively, from the Company’s rights under its option to license certain intellectual property rights related to SPY003 from Paragon until all project antibodies under the SPY003 research program have been selected; (b) reducing the development costs invoiced to the Company for the SPY003 research program incurred from and after April 1, 2024 through completion of the SPY003 antibody selection process by 50%; (c) requiring Paragon to reimburse the Company for 50% of the development costs for the SPY003 research program incurred prior to April 1, 2024; provided, that Paragon receives rights to at least one SPY003 project antibody following completion of the SPY003 antibody selection process; (d) obligating the Company to exercise its option to license the intellectual property rights to SPY003 project antibodies and technology following the completion of the SPY003 antibody selection process; and (e) establishing a license agreement term sheet for the SPY003 research program with substantially similar milestone payment terms and royalty payment terms as the SPY001 License Agreement. See Note 9 for disclosures related to the License Agreements entered into with Paragon.

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2025 shares
Trading Arrangements, by Individual
Non-Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Terminated	false
Scott Burrows [Member]
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	On November 10, 2025, Scott Burrows, our Chief Financial Officer, terminated a trading plan dated April 15, 2024 intended to satisfy Rule 10b5-1(c) to sell up to 180,000 shares of our common stock over a period ending November 19, 2026, subject to certain conditions, and adopted a trading plan intended to satisfy Rule 10b5-1(c) to sell up to 180,000 shares of our common stock over a period ending February 3, 2028, subject to certain conditions.
Scott Burrows November 2025 Plan [Member] \| Scott Burrows [Member]
Trading Arrangements, by Individual
Name	Scott Burrows
Title	Chief Financial Officer
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	November 10, 2025
Expiration Date	February 3, 2028
Arrangement Duration	815 days
Aggregate Available	180,000
Scott Burrows April 2024 Plan [Member] \| Scott Burrows [Member]
Trading Arrangements, by Individual
Name	Scott Burrows
Title	Chief Financial Officer
Rule 10b5-1 Arrangement Terminated	true
Termination Date	November 10, 2025
Aggregate Available	180,000

Income Taxes - Schedule of (Loss) Income Before Income Tax Expense by Jurisdiction (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Domestic	$ (155,255)	$ (207,965)	$ (338,942)
Foreign	37	(2)	126
Loss before income tax expense	$ (155,218)	$ (207,967)	$ (338,816)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
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Reference 3: http://www.xbrl.org/2003/role/exampleRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
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-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 7: http://www.xbrl.org/2003/role/exampleRef
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-URI https://asc.fasb.org/1943274/2147482785/280-10-55-48

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 270
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-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 280
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-Subparagraph (ee)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 12: http://fasb.org/us-gaap/role/ref/otherTransitionRef
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-Name Accounting Standards Codification
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-Paragraph 32
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
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-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.7-04(11))
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-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 14: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
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-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-31

Reference 15: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 16: http://fasb.org/us-gaap/role/ref/legacyRef
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+ Details

Defined Contribution Plan	12 Months Ended
Defined Contribution Plan	Dec. 31, 2025
Retirement Benefits [Abstract]
Defined Contribution Plan	Defined Contribution Plan The Company sponsors a 401(k) retirement plan in which substantially all of its full-time employees are eligible to participate. Participants may contribute a percentage of their annual compensation to this plan, subject to statutory limitations. During the years ended December 31, 2025, 2024, 2023, the Company provided $0.8 million, $0.5 million, and $0.2 million, respectively, in contributions to the plan.

Net Loss Per Share - Schedule of Weighted-Average Equity Instruments Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Options to purchase common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	1,785,568	3,212,734	2,583,226
Unvested restricted stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	27,806	68,027	4,240
Outstanding Parapyre Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	1,532,591	686,724	5,625

Fair Value Measurements - Schedule of Significant Inputs used to Estimate the Fair Value of Derivative Liability (Details) - Level 3 - CVR Liability	Dec. 31, 2025
Minimum \| Estimated probability of success
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative liability, measurement input	0
Minimum \| Estimated reimbursement rate compared to reimbursement target
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative liability, measurement input	0.45
Minimum \| Risk-adjusted discount rates
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative liability, measurement input	0.0985
Maximum \| Estimated probability of success
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative liability, measurement input	0.72
Maximum \| Estimated reimbursement rate compared to reimbursement target
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative liability, measurement input	0.55
Maximum \| Risk-adjusted discount rates
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative liability, measurement input	0.0997

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2025

Income Tax Disclosure [Abstract]

Schedule of (Loss) Income Before Income Tax Expense by Jurisdiction

The following table summarizes the (loss) income before income tax expense by jurisdiction for the periods indicated (in thousands):


	Year Ended December 31,
	2025		2024		2023
Domestic	$	(155,255)	$	(207,965)	$	(338,942)
Foreign	37		(2)		126
Loss before income tax expense	$	(155,218)	$	(207,967)	$	(338,816)

Schedule of Effective Income Tax Rate Reconciliation

The difference between the Company's provision for income taxes and the amounts computed by applying the statutory federal income tax rate to income before income taxes for the year ended December 31, 2025 is as follows (in thousands):


	Year Ended December 31, 2025
	Amount		%
Income taxes (benefit) at statutory federal rate	$	(32,596)	21.00	%
State and local taxes, net of federal income tax effect	—		—	%
Foreign tax effects
Other foreign	(23)		0.01	%
Changes in valuation allowance	37,622		(24.24)	%
Non-taxable or nondeductible items
Stock compensation	773		(0.50)	%
Change in fair market value of contingent value right	(6,251)		4.03	%
Limitation on officers' compensation	2,860		(1.84)	%
Permanent and other items	114		(0.07)	%
Other
Other	10		(0.01)	%
Stock based compensation - deferred only	(2,524)		1.63	%
Provision / (benefit) for income taxes	$	(15)	0.01	%

As disclosed for the years ended December 31, 2024 and 2023, prior to the adoption of ASU 2023-09, the difference between the Company's provision for income taxes and the amounts computed by applying the statutory federal income tax rate to income before income taxes is as follows (in thousands):


	Year Ended December 31,
	2024		2023
Tax provision derived by applying the federal statutory rate to income before income taxes	$	(43,673)	$	(71,151)
Loss on forward contract valuation	—		17,541
Acquired IPR&D	—		27,340
Loss on CVR revaluation	4,290		3,987
Other permanent differences	1,865		4,472
Federal tax credits	(91)		(1)

Effect of tax rate on foreign jurisdiction	(2)		(53)
Other, net	191		—
Change in the valuation allowance	37,471		17,839
Income tax (benefit) expense	$	51	$	(26)

Schedule of Cash Income Taxes Paid

The amounts of cash income taxes paid by the company are as follows:


	Year Ended December 31, 2025
Federal	$	—
State	—
Foreign	(15)
Total	$	(15)

Schedule of Components of Deferred Tax Assets and Liabilities

The components of the deferred tax assets and liabilities consist of the following (in thousands):


	December 31,
	2025		2024		2023
Deferred tax assets
Net operating loss carryforward	$	118,511	$	87,321	$	74,454
Capitalized 174 R&D costs	44,465		45,531		22,532
Intangible assets	4,070		2,117		47

Accrued expense	1,625		1,047		579
Stock-based compensation	12,943		7,114		4,246
Federal tax credits	18,196		18,196		21,914
State tax credits	1,631		1,631		1,631
Other	87		64		88
Total deferred tax assets	201,528		163,021		125,491
Deferred tax liabilities
Unrealized gain	(183)		(92)		—

Total deferred tax liabilities	(183)		(92)		—
Less: Valuation allowance	(201,345)		(162,929)		(125,491)
Deferred tax assets, net	$	—	$	—	$	—

Accrued and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2025

Accrued Liabilities and Other Liabilities [Abstract]

Schedule of Accrued and Other Current Liabilities

Accrued and other current liabilities consist of the following (in thousands):


	December 31,
	2025		2024
Accrued compensation	$	7,940	$	5,688
Accrued contracted research and development costs	17,424		20,861
Accrued professional and consulting fees	1,404		661
Other	179		501
Total accrued and other current liabilities	$	26,947	$	27,711

Fair Value Measurements - Schedule of Changes in Forward Contract Liability (Details) - Forward Contracts $ in Millions	6 Months Ended
	Dec. 31, 2023 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 106.2
Change in fair value	83.5
Issuance of Series A Preferred Stock on July 7, 2023	(189.7)
Ending balance	$ 0.0

Restructuring Charges

12 Months Ended

Dec. 31, 2025

Restructuring and Related Activities [Abstract]

Restructuring Charges

Severance and Stock Compensation

On April 12, 2023, based on the review of the inconclusive interim results from the Company's Phase 1/2 clinical trial of pegtarviliase for the treatment of classical homocystinuria and other business considerations, the Company announced that it had initiated a process to explore strategic alternatives to maximize stockholder value and engaged an independent exclusive financial advisor to support this process.

As a result, the Company implemented a restructuring plan resulting in an approximate 83% reduction of the Company’s existing headcount by June 30, 2023. The Company recognized restructuring expenses consisting of cash severance payments and other employee-related costs of $6.4 million during the year ended December 31, 2023. Cash payments for employee related restructuring charges of $5.3 million were paid as of December 31, 2023. In addition, the Company recognized $1.0 million in non-cash stock-based compensation expense related to the accelerated vesting of stock-based awards for certain employees. The Company recorded these restructuring charges based on each employee’s role to the respective research and development and general and administrative operating expense categories on its consolidated statements of operations and comprehensive loss.

Sale of Assets

During the second quarter of 2023, the Company sold various lab equipment, consumables, and furniture and fixtures for total consideration of $0.5 million. After recording the disposal of all the Company's property and equipment net of proceeds, the Company recorded a $0.7 million and $0.2 million loss on disposal of long-lived assets which is included in Research and development and General and administrative expenses, respectively.

Lease Right-of-use Asset and Leasehold Improvement Impairment

Effective June 30, 2023, the Company abandoned its leased office space in Austin, Texas. As a result, the Company recognized an impairment loss of $0.9 million related to the operating lease right-of-use asset and $1.7 million related to leasehold improvements. On August 7, 2023, the Company terminated its building lease in Austin, Texas. The negotiated termination agreement obligated the Company to pay the lessor a $2.0 million termination fee in exchange for releasing the Company of all further obligations under the lease.

All charges related to the restructuring activities were recognized during the second quarter of 2023. No further restructuring charges will be incurred under the restructuring plan. A summary of the charges related to the restructuring activities is as follows (in thousands):


	Severance Related Expenses		Stock Compensation Expenses		Loss on Disposal of Long-Lived Assets		Lease Asset Impairment		Total Restructuring Costs
Research and development	$	3,182	$	123	$	749	$	1,405	$	5,459
General and administrative	3,266		870		182		1,175		5,493
Total	$	6,448	$	993	$	931	$	2,580	$	10,952

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Amount
Income taxes (benefit) at statutory federal rate	$ (32,596)	$ (43,673)	$ (71,151)
State and local taxes, net of federal income tax effect	0
Other foreign	(23)
Changes in valuation allowance	37,622	37,471	17,839
Stock compensation	773
Change in fair market value of contingent value right	(6,251)
Limitation on officers' compensation	2,860
Permanent and other items	114	1,865	4,472
Other	10	191	0
Stock based compensation - deferred only	(2,524)
Loss on forward contract valuation		0	17,541
Acquired IPR&D		0	27,340
Loss on CVR revaluation		4,290	3,987
Federal tax credits		(91)	(1)
Effect of tax rate on foreign jurisdiction		(2)	(53)
Provision / (benefit) for income taxes	$ (15)	$ 51	$ (26)
Percent
Income taxes (benefit) at statutory federal rate	21.00%
State and local taxes, net of federal income tax effect	0.00%
Other foreign	0.01%
Changes in valuation allowance	(24.24%)
Stock compensation	(0.50%)
Change in fair market value of contingent value right	4.03%
Limitation on officers' compensation	(1.84%)
Permanent and other items	(0.07%)
Other	(0.01%)
Stock based compensation - deferred only	1.63%
Provision / (benefit) for income taxes	0.01%

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Financial Assets
Money market funds	$ 83,991	$ 87,734
Total financial assets	754,803	601,405
Liabilities:
CVR liability	26,680	61,700
Total liabilities	26,680	61,700
Money market funds
Financial Assets
Money market funds	74,004	65,902
U.S. government treasury securities
Financial Assets
Financial Assets	266,064	227,244
U.S. government agency securities
Financial Assets
Financial Assets	119,590	86,681
Commercial paper
Financial Assets
Financial Assets	194,355	165,130
Corporate bonds
Financial Assets
Financial Assets	100,790	56,448
Level 1
Financial Assets
Total financial assets	340,068	293,146
Liabilities:
CVR liability	0	0
Total liabilities	0	0
Level 1 \| Money market funds
Financial Assets
Money market funds	74,004	65,902
Level 1 \| U.S. government treasury securities
Financial Assets
Financial Assets	266,064	227,244
Level 1 \| U.S. government agency securities
Financial Assets
Financial Assets	0	0
Level 1 \| Commercial paper
Financial Assets
Financial Assets	0	0
Level 1 \| Corporate bonds
Financial Assets
Financial Assets	0	0
Level 2
Financial Assets
Total financial assets	414,735	308,259
Liabilities:
CVR liability	0	0
Total liabilities	0	0
Level 2 \| Money market funds
Financial Assets
Money market funds	0	0
Level 2 \| U.S. government treasury securities
Financial Assets
Financial Assets	0	0
Level 2 \| U.S. government agency securities
Financial Assets
Financial Assets	119,590	86,681
Level 2 \| Commercial paper
Financial Assets
Financial Assets	194,355	165,130
Level 2 \| Corporate bonds
Financial Assets
Financial Assets	100,790	56,448
Level 3
Financial Assets
Total financial assets	0	0
Liabilities:
CVR liability	26,680	61,700
Total liabilities	26,680	61,700
Level 3 \| Money market funds
Financial Assets
Money market funds	0	0
Level 3 \| U.S. government treasury securities
Financial Assets
Financial Assets	0	0
Level 3 \| U.S. government agency securities
Financial Assets
Financial Assets	0	0
Level 3 \| Commercial paper
Financial Assets
Financial Assets	0	0
Level 3 \| Corporate bonds
Financial Assets
Financial Assets	$ 0	$ 0

Restructuring Charges - Schedule of Charges Related to the Restructuring Activities (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Jun. 30, 2023	Jun. 30, 2023	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Restructuring Cost and Reserve [Line Items]
Severance Related Expenses					$ 6,400
Loss on Disposal of Long-Lived Assets			$ 0	$ 0	$ 915
Lease Asset Impairment	$ 900
Research and development
Restructuring Cost and Reserve [Line Items]
Loss on Disposal of Long-Lived Assets		$ 700
General and administrative
Restructuring Cost and Reserve [Line Items]
Loss on Disposal of Long-Lived Assets		200
Restructuring Activities
Restructuring Cost and Reserve [Line Items]
Severance Related Expenses		6,448
Stock Compensation Expenses		993
Loss on Disposal of Long-Lived Assets		931
Lease Asset Impairment		2,580
Total Restructuring Costs		10,952
Restructuring Activities \| Research and development
Restructuring Cost and Reserve [Line Items]
Severance Related Expenses		3,182
Stock Compensation Expenses		123
Loss on Disposal of Long-Lived Assets		749
Lease Asset Impairment		1,405
Total Restructuring Costs		5,459
Restructuring Activities \| General and administrative
Restructuring Cost and Reserve [Line Items]
Severance Related Expenses		3,266
Stock Compensation Expenses		870
Loss on Disposal of Long-Lived Assets		182
Lease Asset Impairment		1,175
Total Restructuring Costs		$ 5,493

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

Net Loss Per Share

12 Months Ended

Dec. 31, 2025

Earnings Per Share [Abstract]

Net Loss Per Share

The Company computes net loss per share of common stock, Series A Preferred Stock, and Series B Preferred Stock using the two-class method required for multiple classes of common stock and other participating securities.

The two-class method is an earnings (loss) allocation method under which earnings (loss) per share is calculated for each class of common stock. The Company has determined that the Series A Preferred Stock and Series B Preferred Stock do not have preferential rights when compared to the Company's common stock and therefore it must allocate losses to these other classes of common stock, as illustrated in the table below.

Basic and diluted net loss per share is computed by dividing the net loss by the weighted-average number of shares and pre-funded warrants outstanding during the period, without consideration of potential dilutive securities. The pre-funded warrants are included in the computation of basic net loss per share as the exercise price is negligible and they are fully vested and exercisable. For periods in which the Company generated a net loss, the Company does not include potential shares of common stock in diluted net loss per share when the impact of these items is anti-dilutive. The Company has generated a net loss for all periods presented, therefore diluted net loss per share is the same as basic net loss per share since the inclusion of potential shares of common stock would be anti-dilutive.

The following table sets forth the computation of basic and diluted net loss per share of common stock, Series A Preferred Stock, and Series B Preferred Stock (in thousands, except share and per share amounts):


	Year Ended December 31, 2025
	Series A Preferred Stock		Series B Preferred Stock		Common Stock
Net loss per share, basic and diluted:
Numerator
Allocation of losses	$	(27,344)	$	(1,317)	$	(126,541)
Denominator
Weighted-average shares outstanding	346,045		16,667		64,056,442


Net loss per share, basic and diluted	$	(79.02)	$	(79.02)	$	(1.98)

	Year Ended December 31, 2024
	Series A Preferred Stock		Series B Preferred Stock		Common Stock
Net loss per share, basic and diluted:
Numerator
Allocation of losses	$	(47,624)	$	(10,839)	$	(149,555)
Denominator
Weighted-average shares outstanding	374,387		85,208		46,940,206
Weighted-average pre-funded warrants outstanding	—		—		87,432
Number of shares used in per share computation	374,387		85,208		47,027,638
Net loss per share, basic and diluted	$	(127.21)	$	(127.21)	$	(3.18)

	Year Ended December 31, 2023
	Series A Preferred Stock		Series B Preferred Stock		Common Stock
Net loss per share, basic and diluted:
Numerator
Allocation of losses	$	(239,158)	$	(4,749)	$	(94,883)
Denominator
Weighted-average shares outstanding	434,612		8,630		6,201,954
Weighted-average pre-funded warrants outstanding	—		—		695,111
Number of shares used in per share computation	434,612		8,630		6,897,065
Net loss per share, basic and diluted	$	(550.28)	$	(550.29)	$	(13.76)

The following weighted-average equity instruments were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive for the periods presented:


	Year Ended December 31,
	2025	2024	2023
Options to purchase common stock	1,785,568	3,212,734	2,583,226
Unvested restricted stock units	27,806	68,027	4,240
Outstanding Parapyre Warrants	1,532,591	686,724	5,625.00

Licensing Agreements (Details) - Related Party - USD ($)			12 Months Ended
	Oct. 11, 2024	May 14, 2024	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Reimbursable costs under the Paragon Agreement
Related Party Transaction [Line Items]
Campaign timeline, minimum term			5 years
Royalty step-down percentage			33.00%
Royalty term expiration period			12 years
Termination notice period			60 days
Sublicensing fee			$ 1,900,000	$ 700,000	$ 0
Milestone expense recognized			8,500,000	9,500,000	0
Milestone payments, outstanding and payable			0	0
Milestone payments			8,500,000	9,500,000	0
Sublicensing fee payments			2,400,000	200,000	$ 0
SPY001 License Agreement
Related Party Transaction [Line Items]
Milestone payments		$ 3,000,000.0
SPY002 License Agreement
Related Party Transaction [Line Items]
Milestone payments		3,000,000.0
SPY003 License Agreement
Related Party Transaction [Line Items]
Milestone payments	$ 3,000,000.0
License Agreements milestone and sublicensing fees
Related Party Transaction [Line Items]
Sublicensing fees, outstanding and payable			0	$ 500,000
Maximum \| SPY001 License Agreement
Related Party Transaction [Line Items]
Contingent obligation based on milestones		22,000,000.0
Maximum \| SPY002 License Agreement
Related Party Transaction [Line Items]
Contingent obligation based on milestones		$ 22,000,000.0
Sublicensing fee			$ 20,000,000.0
Maximum \| SPY003 License Agreement
Related Party Transaction [Line Items]
Contingent obligation based on milestones	$ 22,000,000.0

Segment Reporting - Schedule of Significant Expenses Provided to the CODM on a Regular Basis (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Revenue	$ 0	$ 0	$ 886
Less:
Share-based compensation	37,614	44,833	25,675
Net loss	155,203	208,018	338,790
Reconciliation of net loss
Adjustments and reconciling items	155,203	208,018	338,790
Net loss	155,203	208,018	338,790
Increase (decrease) in fair value of contingent value right liability	(29,800)	20,400	18,900
Related Party
Less:
Share-based compensation	1,000	15,600	11,500
Research and development, excluding compensation and stock-based compensation	10,500	25,500	37,100
Reportable Segment
Less:
Net loss	155,203	208,018	338,790
Reconciliation of net loss
Adjustments and reconciling items	155,203	208,018	338,790
Net loss	155,203	208,018	338,790
Reportable Segment \| Operating Segments
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Revenue	0	0	886
Less:
Compensation	34,794	21,780	22,590
Share-based compensation	37,614	44,833	25,675
Research and development, excluding compensation and stock-based compensation	132,490	127,491	65,282
Other segment items	(49,695)	13,914	226,129
Net loss	155,203	208,018	338,790
Reconciliation of net loss
Adjustments and reconciling items	155,203	208,018	338,790
Net loss	155,203	208,018	338,790
Reportable Segment \| Adjustments and reconciling items
Less:
Net loss	0	0	0
Reconciliation of net loss
Adjustments and reconciling items	0	0	0
Net loss	$ 0	$ 0	$ 0

Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
Income Taxes - Narrative (Details) - USD ($)	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Income Tax Contingency [Line Items]
Provision or benefit from income taxes	$ (15,000)	$ 51,000	$ (26,000)
Increase in valuation primarily due to operation losses	38,400,000	37,400,000	$ 17,800,000
Net operating loss carryforwards	560,100,000	415,800,000
Net operating loss carryforwards, set to expire if not utilized	58,400,000	58,400,000
Tax credit carryforwards, set to expire if not utilized	20,300,000	20,300,000
Unrecognized tax benefits	0	0
U.S
Income Tax Contingency [Line Items]
Tax credit carryforwards	18,200,000	18,200,000
State
Income Tax Contingency [Line Items]
Tax credit carryforwards	$ 2,100,000	$ 2,100,000

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2025

Accounting Policies [Abstract]

Basis of Presentation

The consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States (“U.S. GAAP”) as defined by the Financial Accounting Standards Board (“FASB”) and include the accounts of the Company and its wholly owned subsidiaries.

Consolidation

All intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

Cash and Cash Equivalents

Marketable Securities

Restricted Cash

Concentration of Credit Risk

Property and Equipment

Impairment of Long-Lived Assets

Accrued Research and Development Costs

License Agreements Contingent Milestone Payments

Leases

Fair Value of Financial Instruments

The three levels of inputs that may be used to measure fair value are as follows:


Level 1:			Observable inputs, such as quoted prices in active markets for identical assets or liabilities.

Level 2:			Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

Level 3:			Valuations based on unobservable inputs to the valuation methodology and including data about assumptions that market participants would use in pricing the asset or liability based on the best information available under the circumstances.

Revenue Recognition

The Company assesses its license arrangements within the scope of Topic 606 in accordance with this framework as follows:

License revenue

discretion are generally considered options. The Company assesses if these options provide a material right to the customer and if so, they are considered performance obligations.

Collaborative arrangements

Research and Development Costs

Stock-Based Compensation

Convertible Preferred Stock Issued through PIPE

Contingent Milestone Proceeds

Acquisitions

Contingent Value Rights

Income Taxes

noncurrent along with the related valuation allowance. Due to a lack of earnings history, the net deferred tax assets have been fully offset by a valuation allowance.

Comprehensive Loss

Recently Adopted Accounting Pronouncements and Not Yet Adopted Accounting Pronouncements

Recently Adopted Accounting Pronouncements

Not Yet Adopted Accounting Pronouncements

Net Loss Per Share

Income Taxes

12 Months Ended

Dec. 31, 2025

Income Tax Disclosure [Abstract]

Income Taxes

The following table summarizes the (loss) income before income tax expense by jurisdiction for the periods indicated (in thousands):


	Year Ended December 31,
	2025		2024		2023
Domestic	$	(155,255)	$	(207,965)	$	(338,942)
Foreign	37		(2)		126
Loss before income tax expense	$	(155,218)	$	(207,967)	$	(338,816)


	Year Ended December 31, 2025
	Amount		%
Income taxes (benefit) at statutory federal rate	$	(32,596)	21.00	%
State and local taxes, net of federal income tax effect	—		—	%
Foreign tax effects
Other foreign	(23)		0.01	%
Changes in valuation allowance	37,622		(24.24)	%
Non-taxable or nondeductible items
Stock compensation	773		(0.50)	%
Change in fair market value of contingent value right	(6,251)		4.03	%
Limitation on officers' compensation	2,860		(1.84)	%
Permanent and other items	114		(0.07)	%
Other
Other	10		(0.01)	%
Stock based compensation - deferred only	(2,524)		1.63	%
Provision / (benefit) for income taxes	$	(15)	0.01	%


	Year Ended December 31,
	2024		2023
Tax provision derived by applying the federal statutory rate to income before income taxes	$	(43,673)	$	(71,151)
Loss on forward contract valuation	—		17,541
Acquired IPR&D	—		27,340
Loss on CVR revaluation	4,290		3,987
Other permanent differences	1,865		4,472
Federal tax credits	(91)		(1)

Effect of tax rate on foreign jurisdiction	(2)		(53)
Other, net	191		—
Change in the valuation allowance	37,471		17,839
Income tax (benefit) expense	$	51	$	(26)

The amounts of cash income taxes paid by the company are as follows:


	Year Ended December 31, 2025
Federal	$	—
State	—
Foreign	(15)
Total	$	(15)

The components of the deferred tax assets and liabilities consist of the following (in thousands):


	December 31,
	2025		2024		2023
Deferred tax assets
Net operating loss carryforward	$	118,511	$	87,321	$	74,454
Capitalized 174 R&D costs	44,465		45,531		22,532
Intangible assets	4,070		2,117		47

Accrued expense	1,625		1,047		579
Stock-based compensation	12,943		7,114		4,246
Federal tax credits	18,196		18,196		21,914
State tax credits	1,631		1,631		1,631
Other	87		64		88
Total deferred tax assets	201,528		163,021		125,491
Deferred tax liabilities
Unrealized gain	(183)		(92)		—

Total deferred tax liabilities	(183)		(92)		—
Less: Valuation allowance	(201,345)		(162,929)		(125,491)
Deferred tax assets, net	$	—	$	—	$	—

The Company has established a full federal and state valuation allowance equal to the net deferred tax assets due to uncertainties regarding the realization of the deferred tax asset based on the Company’s lack of earnings history. The valuation allowance increased by $38.4 million, $37.4 million, and $17.8 million during the years ended December 31, 2025, 2024, and 2023, respectively, primarily due to continuing loss from operations.

As of December 31, 2025 and 2024, the Company had U.S. net operating loss carryforwards (“NOL”) of $560.1 million and $415.8 million, respectively.

For the year ended December 31, 2025, the Company had U.S. tax credit carryforwards and state tax credit carryforwards of $18.2 million and $2.1 million, respectively. Of the net operating loss and tax credit carryforwards $58.4 million and $20.3 million will begin to expire in 2033 and 2034, respectively.

For the year ended December 31, 2024, the Company had U.S. tax credit carryforwards and state tax credit carryforwards of $18.2 million and $2.1 million, respectively. Of the net operating loss and tax credit carryforwards $58.4 million and $20.3 million will begin to expire in 2033 and 2034, respectively, if not utilized. Any remaining net operating loss will carry forward indefinitely and can be utilized to offset up to 80% of the taxable income in any tax year. The net operating loss and credit carryforwards are subject to Internal Revenue Service adjustments until the statute closes on the year the net operating loss or tax credits are utilized.

The Company has not completed a study to assess whether an ownership change has occurred or whether there have been multiple ownership changes since the Company’s formation due to the complexity and cost associated with such a study, and the fact that there may be additional such ownership changes in the future. If the Company has experienced an ownership change at any time since its formation, utilization of the NOL or research and development credit carryforwards would be subject to an annual limitation under Section 382 or 383 of the Internal Revenue Code, which is determined by first multiplying the value of the Company’s stock at the time of the ownership change by the applicable long-term, tax-exempt rate, and then could be subject to additional adjustments, as required. Additionally, the separate return limitation year (“SRLY”) rules may apply to losses of the Company’s eight wholly owned U.S. subsidiary corporations that have now been merged with the parent company. The SRLY rules limit the consolidated group’s use of a subsidiary corporation’s net operating losses to the amount of income generated by the subsidiary corporation after it becomes a member of the group. Any limitation may result in expiration of a portion of the NOL or research and development credit carryforwards before utilization. Further, until a study is completed and any limitation known, no amounts are being considered as an uncertain tax position or disclosed as an unrecognized tax benefit.

Additionally, the Company does not expect any unrecognized tax benefits to change significantly over the next twelve months. Due to the existence of the valuation allowance, future changes in the Company’s unrecognized tax benefits will not impact its effective tax rate. Any carryforwards that will expire prior to utilization as a result of such limitations will be removed from deferred tax assets with a corresponding reduction of the valuation allowance.

The Company is subject to examination by taxing authorities in its significant jurisdictions for the year ended 2021 and subsequent years. However, due to NOL and tax attribute carryovers, the taxing authorities have the ability to adjust the NOLs and other tax attributes related to closed years. As of December 31, 2025 and 2024, there were no amounts recorded for uncertain tax positions. As of December 31, 2025, undistributed earnings of the Company’s incorporated foreign subsidiaries are immaterial. Under the Global Intangible Low-Taxed Income (“GILTI”) provisions of the 2017 Tax Cuts and Jobs Act, U.S. income taxes have been incurred on the undistributed earnings of the foreign subsidiaries and therefore, the tax impact upon distribution is limited to state income and withholding taxes and is not material.

- Definition

The entire disclosure for income tax.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 740
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
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-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
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-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 10
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-Section 50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12

Reference 5: http://www.xbrl.org/2003/role/exampleRef
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-Section 55
-Paragraph 231
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482663/740-10-55-231

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 10
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-Section 50
-Paragraph 12C
-Publisher FASB
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12B

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
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-Paragraph 1
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
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-URI https://asc.fasb.org/740/tableOfContent

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
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-Section 50
-Paragraph 14
-Publisher FASB
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-21

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
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-Section 50
-Paragraph 17
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-Publisher FASB
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482603/740-30-50-2

+ Details

Strategic License Agreements	12 Months Ended
Strategic License Agreements	Dec. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Strategic License Agreements	Strategic License Agreements Immedica Pharma AB License and Development Agreement On March 21, 2021, the Company entered into an exclusive license and supply agreement with Immedica Pharma AB (“Immedica”). By entering into this agreement, the Company agreed to provide Immedica the following goods and services: i.Deliver an exclusive, sublicensable, license and know-how (the “License”) to develop and commercialize pegzilarginase (the “Product”) in the territory comprising the member states of the European Economic Area, United Kingdom, Switzerland, Andorra, Monaco, San Marino, Vatican City, Turkey, Saudi Arabia, United Arab Emirates, Qatar, Kuwait, Bahrain, and Oman (the “Territory”); ii.Complete the global pivotal PEACE (Pegzilarginase Effect on Arginase 1 Deficiency Clinical Endpoints) Phase 3 trial (“PEACE Trial”) and related Biologics License Application (“BLA”) package to file with the United States Food and Drug Administration (“FDA”), which will be leveraged by Immedica in obtaining the necessary regulatory approvals in the Territory; and iii.Perform a Pediatric Investigation Plan trial (“PIP Trial”) in order for Immedica to be able to receive certain regulatory approvals within the Territory. In addition, the Company and Immedica formed a Joint Steering Committee (“JSC”) to provide oversight to the activities performed under the agreement; however, the substance of the Company’s participation in the JSC does not represent an additional promised service, but rather, a right of the Company to protect its own interests in the arrangement. Further, the Company agreed to supply to Immedica, and Immedica agreed to purchase from the Company, substantially all commercial requirements of the Product. The terms of the agreement do not provide for either (i) an option to Immedica to purchase the Product from the Company at a discount from the standalone selling price or (ii) minimum purchase quantities. Finally, Immedica will bear (i) all costs and expenses for any development or commercialization of the Product in the Territory subject to the License exclusive of the Company’s promised goods and services summarized above and (ii) all costs and fees associated with applying for regulatory approval of the Product in the Territory. In July 2021, the Company modified the agreement with Immedica to provide certain additional services in relation to the PEACE Phase 3 Trial and BLA package performance obligation in exchange for the reimbursement of up to $3.0 million of the actual costs incurred in relation to such incremental services. For the year ended December 31, 2023, the Company recognized revenue of $0.9 million related to the PEACE Trial and BLA package performance obligation using a cost to cost model. On July 27, 2023, the Company announced that it had entered into an agreement to sell the global rights to pegzilarginase to Immedica for $15.0 million in upfront cash proceeds and up to $100.0 million in contingent milestone payments. The sale of pegzilarginase to Immedica superseded and terminated the previous license agreement between the Company and Immedica. On July 27, 2023, the carrying value of the asset was zero as it was internally developed. Accordingly, the Company recognized a $16.4 million gain within Gain on Sale of in-process research and development, which is comprised of $15.0 million in upfront cash proceeds and the reimbursement of $1.8 million in pre-paid manufacturing costs that was contingent upon a favorable opinion being received by the CHMP, net of transaction costs and the derecognition of pegzilarginase related nonfinancial assets and liabilities totaling $0.4 million. The milestone payments are contingent on formal reimbursement decisions by national authorities in key European markets and pegzilarginase approval by the FDA, among other events. The upfront payment and contingent milestone payments if paid, net of expenses and adjustments, will reduce the CVR liability and will be distributed to CVR holders pursuant to the CVR Agreement resulting from the Asset Acquisition. During the twelve months ended December 31, 2025, the Company recognized a gain of $10.0 million within Gain on Sale of in-process research and development, for achieving certain reimbursement decision milestones during the period. As of December 31, 2025, $3.0 million remains outstanding and reflected in Prepaid expenses and other current assets. There was no similar gain during the twelve months ended or similar receivable as of December 31, 2024. Contract Balances from Customer Contract The timing of revenue recognition, billings and cash collections results in contract assets and contract liabilities on the balance sheets. The Company recognizes license and development receivables based on billed services, which are derecognized upon reimbursement. When consideration is received, or such consideration is unconditionally due, from a customer prior to transferring goods or services to the customer under the terms of a contract, a contract liability is recorded. Contract liabilities are recognized as revenue after control of the goods or services is transferred to the customer and all revenue recognition criteria have been met. The Company had no contract assets or liabilities during the years ended December 31, 2025 and 2024.

Income Taxes - Schedule of Cash Income Taxes Paid (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2025 USD ($)
Income Tax Disclosure [Abstract]
Federal	$ 0
State	0
Foreign	(15)
Total	$ (15)

Income Taxes - Schedule of Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Deferred tax assets
Net operating loss carryforward	$ 118,511	$ 87,321	$ 74,454
Capitalized 174 R&D costs	44,465	45,531	22,532
Intangible assets	4,070	2,117	47
Accrued expense	1,625	1,047	579
Stock-based compensation	12,943	7,114	4,246
Other	87	64	88
Total deferred tax assets	201,528	163,021	125,491
Deferred tax liabilities
Unrealized gain	(183)	(92)	0
Total deferred tax liabilities	(183)	(92)	0
Less: Valuation allowance	(201,345)	(162,929)	(125,491)
Deferred tax assets, net	0	0	0
Federal tax credits
Deferred tax assets
Tax credits	18,196	18,196	21,914
State tax credits
Deferred tax assets
Tax credits	$ 1,631	$ 1,631	$ 1,631

Stock-Based Compensation

12 Months Ended

Dec. 31, 2025

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

2016 Equity Incentive Plan

The 2016 Plan became effective in April 2016 and serves as the successor to the 2015 Equity Incentive Plan ("2015 Plan"). Under the 2016 Plan, the Company may grant stock options, stock appreciation rights, restricted stock awards, restricted stock units, performance awards, and stock bonuses. The 2016 Plan

provides for an initial reserve of 44,000 shares of common stock, plus 20,395 shares of common stock remaining under the 2015 Plan, and any share awards that subsequently are forfeited or lapse unexercised under the 2015 Plan. The shares reserved exclude shares of common stock reserved for issuance under the 2015 Plan.

In October 2018, the 2016 Plan was amended to increase the number of shares of common stock reserved for issuance thereunder by 70,384 shares, extend the term of the 2016 Plan through August 7, 2028, and provide for an automatic increase in the number of shares reserved for issuance thereunder on January 1 of each year for the remaining term of the plan equal to (a) 4.0% of the number of issued and outstanding shares of common stock on December 31 of the immediately preceding year, or (b) a lesser amount as approved by the board each year (the "Evergreen Provision").

In November 2023, the 2016 Plan was amended to (i) increase the number of shares of common stock reserved for issuance thereunder by 4,481,152 shares, (ii) revise the annual limit on non-employee director compensation from 4,000 shares to (a) $750,000 in total value or (b) $1,000,000 in the year of the director’s initial service as a non-employee director or in any year a director serves as chairman of the Board of Directors, in either case, applicable to fees paid in both cash and equity, (iii) remove the fixed termination date of the 2016 Plan and, (iv) revise the Evergreen Provision from 4% to 5% of issued and outstanding shares of Company common stock on December 31 of the preceding calendar year and to include shares issuable upon the exercise of pre-funded warrants and the conversion of outstanding shares of non-voting convertible preferred stock in the calculation.

As a result of the Evergreen Provision, on January 1, 2025, 2024, and 2023, an additional 3,814,905, 3,023,650, and 104,561 shares, respectively, became available for issuance under the 2016 Plan.

As of December 31, 2025, the total number of shares reserved for issuance under the 2016 Plan was 10,810,714, of which 4,827,082 shares were subject to outstanding option awards and restricted unit awards.

2018 Equity Inducement Plan

In February 2018, the board of directors approved and adopted the 2018 Equity Inducement Plan (as amended, the “2018 Plan”), which became effective on the same date. The board of directors approved an initial reserve of 44,000 shares of common stock to be used exclusively for individuals who were not previously employees or directors, or following a bona fide period of non-employment, as an inducement material to the individual entering into employment with the Company. Nonqualified stock options or restricted stock units may be granted under the 2018 Plan at the discretion of the Compensation Committee or the board of directors. The Company did not seek stockholder approval of the 2018 Plan pursuant to Nasdaq Rule 5635(c)(4).

The 2018 Plan was amended to increase the number of shares of common stock reserved for issuance by 750,000 and 1,000,000 during the years ended December 31, 2025 and 2024, respectively.

As of December 31, 2025, the total number of shares reserved for issuance under the 2018 Plan was 7,460,440, of which 6,620,097 shares were subject to outstanding awards.

Under the 2016 Plan and 2018 Plan, the Company may grant stock-based awards with service conditions (“service-based” awards), performance conditions (“performance-based” awards), and market conditions (“market-based” awards). Service-based awards granted under the 2018 Plan, 2016 Plan, and 2015 Plan generally vest over four years and expire after ten years, although awards have been granted with vesting terms less than four years.

Spyre 2023 Equity Incentive Plan

On June 22, 2023, in connection with the Asset Acquisition, the Company assumed the Amended and Restated Spyre 2023 Equity Incentive Plan (the "Spyre Equity Plan") and its outstanding and unexercised stock options, which were converted to options to purchase 2,734 shares of the Company's common stock. The acquisition-date fair value of these grants will be recognized as an expense on a pro-rata basis over the vesting period. As of December 31, 2025, none of the stock options under the 2023 Plan remained outstanding.

Parapyre Option Obligation

On June 22, 2023, in connection with the Asset Acquisition, the Company assumed the Parapyre Option Obligation which provided for an annual equity grant of warrants for Parapyre to purchase 1% of the then outstanding shares of Pre-Merger Spyre's common stock, on a fully diluted basis, on the last business day of each calendar year during the term of the Paragon Agreement, at the fair market value determined by the board of directors of Pre-Merger Spyre.

On September 29, 2023, the Company amended the Paragon Agreement to amend and restate certain terms of the option grant pertaining to the Parapyre Option Obligation, including but not limited to (i) defining that the annual equity grant of warrants is based on the outstanding shares of the Company’s common stock, on a fully-diluted basis, (ii) establishing the grant date as the last business day of 2023 and 2024, and (iii) defining the term of the warrants granted as ten years. The Company determined that the 2023 and 2024 grants are two separate grants, as there would be no obligation for the 2024 grant had the Company exercised or terminated all of the options under the Paragon Agreement prior to December 31, 2023. The service inception period for the grant precedes the grant date, with the full award being vested as of the grant date with no post-grant date service requirement. Accordingly, a liability related to the Parapyre Option Obligation was recorded pursuant to the amended Paragon Agreement during the 2023 and 2024 interim periods. The Company settled its 2024 and 2023 obligations under the Parapyre Option Obligation by issuing Parapyre 848,184 and 684,407 warrants, respectively, to purchase the Company's common stock at an exercise price per share per warrant of $23.28 and $21.52, respectively. There was no similar expense for the year ended December 31, 2025.

The following table summarizes stock option activity for the year ended December 31, 2025:


	Shares Issuable Under Options	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term	Aggregate Intrinsic Value
				(in years)	(in thousands)
Outstanding as of December 31, 2024	9,253,158	$	15.08	8.80	$	90,016
Granted	2,623,217	19.98
Exercised	(307,673)	8.68
Forfeited	(198,455)	33.38
Outstanding as of December 31, 2025	11,370,247	$	16.06	8.16	$	191,198
Options vested and expected to vest as of December 31, 2025	11,370,247	$	16.06	8.16	$	191,198
Options exercisable as of December 31, 2025	5,164,959	$	14.50	7.95	$	95,153

The aggregate intrinsic value of options outstanding, exercisable, vested and expected to vest were calculated as the difference between the exercise price of the options and the fair value of the Company’s common stock as of the reporting date.

For the years ended December 31, 2025, 2024, and 2023, the weighted-average grant date fair value of options granted was $19.98, $28.39, and $9.67, per share, respectively. The total intrinsic value of options exercised during the years ended December 31, 2025, 2024 and 2023 was $4.0 million, $22.7 million and $0.4 million, respectively.

There were 10,000 and 477,000 stock options issued to non-employees during the years ended December 31, 2024 and 2023, respectively. There were no stock options issued to non-employees during the year ended December 31, 2025. For the year ended December 31, 2025 and 2024, 119,250 and 139,187 non-employee stock options vested in the period, respectively. There were no non-employee stock options vested during the years ended 2023.

2016 Employee Stock Purchase Plan

The 2016 Employee Stock Purchase Plan (“2016 ESPP”) became effective in April 2016. A total of 6,600 shares of common stock were reserved for issuance under the 2016 ESPP. Eligible employees may purchase shares of common stock under the 2016 ESPP at 85% of the lower of the fair market value of the common stock as of the first or the last day of each offering period. Employees are limited to contributing 15% of the employee’s eligible compensation and may not purchase more than $25,000 of stock during any calendar year. The 2016 ESPP will terminate ten years from the first purchase date under the plan, unless terminated earlier by the board of directors.

In June 2018, the 2016 ESPP was amended to provide for an automatic annual increase in the number of shares reserved for issuance thereunder (the "Evergreen Provision") on January 1 of each year for the remaining term of the year equal to (a) 1.0% of the number of issued and outstanding shares of common stock on December 31 of the immediately preceding year, or (b) a lesser amount as approved by the board of directors each year. As a result of the operation of this provision, on January 1, 2025, 2024 and 2023, an additional 602,570, 360,571, and 26,140 shares, respectively, became available for issuance under the 2016 ESPP. As of December 31, 2025, the reserve remaining and available for future issuance under the 2016 ESPP was 972,775 shares.

In February 2023, the 2016 ESPP was amended to increase the maximum shares purchased during any one period (the "ESPP Limit") from 80 shares to 400 shares or a lesser amount determined by the board of directors and in January 2024, the 2016 ESPP was further amended to increase the ESPP Limit to 2,000 shares or a lesser amount determined by the Compensation Committee.

Effective January 1, 2026, the 2016 ESPP was amended and restated (as amended and restated, the "AR 2016 ESPP") to remove the Evergreen Provision, extend the term of the 2016 ESPP indefinitely and re-establish the offering periods, among other changes. The Company plans to submit the AR 2016 ESPP for stockholder approval at its 2026 Annual Meeting of Stockholders.

For the years ended December 31, 2025 and 2024, stock-based compensation expense related to the 2016 ESPP plan was $0.3 million and $0.1 million for the year ended December 31, 2023.

Restricted Stock Units

The following table summarizes employee restricted stock unit activity for the year ended December 31, 2025:


	Shares	Weighted Average Grant Date Fair Value
Unvested restricted stock units as of December 31, 2024	115,398	$	18.17

Vested	(38,466)	18.17

Unvested restricted stock units as of December 31, 2025	76,932	$	18.17

There were no restricted stock units granted during the year ended December 31, 2025.

Stock-Based Compensation Expense


	Year Ended December 31,
	2025				2024				2023
	Employees		Non- Employees		Employees		Non- Employees		Employees		Non- Employees
Research and development (1)	$	16,270	$	—	$	9,112	$	14,459	$	2,910	$	11,328
General and administrative	20,318		1,026		19,833		1,429		11,327		110
Total stock-based compensation expense (2)	$	36,588	$	1,026	$	28,945	$	15,888	$	14,237	$	11,438

No related tax benefits were recognized for the years ended December 31, 2025, 2024, and 2023 (see Note 18).

All outstanding awards as of December 31, 2025, under the 2016 Plan and 2018 Plan, have service-based vesting conditions only.

As of December 31, 2025, the Company had an aggregate of $81.3 million of unrecognized stock-based compensation expense for options outstanding, which is expected to be recognized over a weighted average period of 2.3 years.

In determining the fair value of the stock-based awards, the Company uses the Black-Scholes option-pricing model and assumptions discussed below. Each of these inputs is subjective and generally requires significant judgment to determine.

Expected Term

The Company’s expected term represents the period that the Company’s stock-based awards are expected to be outstanding and is determined using the simplified method (based on the midpoint between the vesting date and the end of the contractual term). The Company utilizes this method due to lack of historical exercise data and the plain-vanilla nature of the Company’s stock-based awards.

Expected Volatility

The Company has limited relevant company-specific historical data to support its expected volatility since the Company's 2023 strategy and pipeline reset . As such, the Company has used an average of expected volatilities based on the volatilities of a representative group of publicly traded biopharmaceutical companies over a period equal to the expected term of the stock option grants. For purposes of identifying comparable companies, the Company selected companies with comparable characteristics to it, including enterprise value, risk profiles, position within the industry, and with historical share price information sufficient to meet the expected life of the stock-based awards. The historical volatility data was computed using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of the stock-based awards. The Company intends to consistently apply this process using the same or similar comparable entities until a sufficient amount of historical information regarding the volatility of the Company’s own share price post transition becomes available.

Risk-Free Interest Rate

The risk-free interest rate is based on the U.S. Treasury zero coupon issues in effect at the time of grant for periods corresponding with the expected term of option.

Expected Dividend

The Company has never paid dividends on its common stock and has no plans to pay dividends on its common stock. Therefore, the Company used an expected dividend yield of zero.

Valuation of Stock Options and 2016 ESPP

The fair value of the stock options granted under the Company's equity incentive plans, as well as the shares available for purchase under the 2016 ESPP were determined using the Black-Scholes option-pricing model. The following table summarizes the weighted-average assumptions used in calculating the fair value of the awards:


	Year Ended December 31,
	2025		2024		2023
Stock Options Granted
Expected term (in years)	5.99		6.03		5.88
Expected volatility	76	%	105	%	107	%
Risk-free interest	4.33	%	4.06	%	4.37	%
Dividend yield	0	%	0	%	0	%
2016 ESPP
Expected term (in years)	0.44		0.50		0.49
Expected volatility	70	%	84	%	181	%
Risk-free interest	4.22	%	5.16	%	4.99	%
Dividend yield	0	%	0	%	0	%

Consolidated Statements of Operations (Parenthetical) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2025

Dec. 31, 2024

Dec. 31, 2023

Research and development

^[1]

$ 171,653

$ 162,790

$ 89,504

General and administrative

^[2]

47,909

45,776

39,946

Related Party

Research and development

10,500

40,100

48,500

General and administrative

$ 1,000

$ 1,100

$ 100

[1]	Includes $10.5 million, $40.1 million and $48.5 million in related party expenses for the years ended December 31, 2025, 2024 and 2023, respectively.
[2]	Includes $1.0 million, $1.1 million and $0.1 million in related party expenses for the years ended December 31, 2025, 2024 and 2023, respectively.

Convertible Preferred Stock and Stockholders’ Equity (Details)													1 Months Ended			3 Months Ended		12 Months Ended
	Oct. 15, 2025 USD ($) $ / shares shares	Nov. 29, 2024 shares	Nov. 20, 2024 USD ($) $ / shares shares	May 14, 2024 shares	Apr. 23, 2024 shares	Mar. 20, 2024 USD ($) $ / shares shares	Mar. 18, 2024 shares	Dec. 11, 2023 USD ($) $ / shares shares	Dec. 08, 2023	Jul. 07, 2023 shares	Jun. 26, 2023 USD ($) $ / shares shares	Jun. 22, 2023	Feb. 12, 2026 USD ($) $ / shares shares	Jun. 30, 2023 shares	May 31, 2022 $ / shares	Dec. 31, 2025 USD ($) Vote $ / shares shares	Dec. 31, 2023 $ / shares shares	Dec. 31, 2025 USD ($) Vote $ / shares shares	Dec. 31, 2024 USD ($) $ / shares shares	Dec. 31, 2023 $ / shares shares	Feb. 28, 2025 USD ($)	Sep. 06, 2024 USD ($)	Apr. 25, 2024 shares	Dec. 31, 2022 shares
Class Of Stock [Line Items]
Shares authorized (in shares)																410,000,000		410,000,000
Common stock, authorized (in shares)																400,000,000		400,000,000	400,000,000
Preferred stock, authorized (in shares)																10,000,000		10,000,000
Convertible preferred stock, par value (in dollars per share) \| $ / shares																$ 0.0001		$ 0.0001
Common stock, par value (in dollars per share) \| $ / shares																$ 0.0001		$ 0.0001	$ 0.0001
Number of votes for common stock holders \| Vote																1		1
Common stock dividends declared \| $																		$ 0	$ 0
Issuance of Series B non-voting convertible preferred stock in connection with private placement, net of financing costs (in shares)								150,000
Exercise price per warrant (in dollars per share) \| $ / shares															$ 0.0025
Maximum ownership percentage of common stock shares for outstanding warrants to be exercised															4.99%
Ownership percentage for outstanding warrants to purchase shares of common stock to be exercised to certain holders															9.99%
Maximum ownership percentage of common stock shares for outstanding warrants to be exercised upon written notice															19.90%
Revised ownership percentage, period to take effect after notice															61 days
Number of warrants outstanding (in shares)																0		0
Parapyre Warrants
Class Of Stock [Line Items]
Warrants to purchase shares (in shares)																	684,407		848,184	684,407
Exercise price per warrant (in dollars per share) \| $ / shares																	$ 21.52		$ 23.28	$ 21.52
Number of warrants exercised (in shares)																0		0
Common Stock
Class Of Stock [Line Items]
Conversion of non-voting convertible preferred stock into common stock (in shares)																			10,198,000
Exchange of Series A non-voting convertible preferred stock for common stock (in shares)																			3,640,000
Common Stock \| Conversion of Series A Non-Voting Convertible Preferred Stock
Class Of Stock [Line Items]
Conversion of non-voting convertible preferred stock into common stock (in shares)																	25,972,080
Common Stock \| Conversion of Series B Non-Voting Convertible Preferred Stock
Class Of Stock [Line Items]
Conversion of non-voting convertible preferred stock into common stock (in shares)				10,198,320															10,198,320
Series B Non-Voting Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, authorized (in shares)																271,625		271,625	271,625
Convertible preferred stock, par value (in dollars per share) \| $ / shares																$ 0.0001		$ 0.0001	$ 0.0001
Issuance of Series B non-voting convertible preferred stock in connection with private placement, net of financing costs (in shares)						121,625	271,625	150,000
Conversion basis						40		40	40
Preferred stock, outstanding (in shares)																16,667		16,667	16,667
Preferred stock, not automatically converted, outstanding (in shares)																16,667		16,667
Series B Non-Voting Convertible Preferred Stock \| Minimum
Class Of Stock [Line Items]
Beneficial holders owned percentage									0.00%
Series B Non-Voting Convertible Preferred Stock \| Maximum
Class Of Stock [Line Items]
Beneficial holders owned percentage									19.90%
Series B Non-Voting Convertible Preferred Stock \| Preferred Stock
Class Of Stock [Line Items]
Issuance of Series B non-voting convertible preferred stock in connection with private placement, net of financing costs (in shares)																			122,000	150,000
Conversion of non-voting convertible preferred stock into common stock (in shares)																			(255,000)
Preferred stock, outstanding (in shares)																17,000	0	17,000	17,000	0				0
Series B Non-Voting Convertible Preferred Stock \| Preferred Stock \| Conversion of Series B Non-Voting Convertible Preferred Stock
Class Of Stock [Line Items]
Conversion of non-voting convertible preferred stock into common stock (in shares)				254,958															254,958
Common Stock
Class Of Stock [Line Items]
Exchange of Series A non-voting convertible preferred stock for common stock (in shares)					3,639,680
Series A Non-Voting Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, authorized (in shares)																1,086,341		1,086,341	1,086,341
Convertible preferred stock, par value (in dollars per share) \| $ / shares																$ 0.0001		$ 0.0001	$ 0.0001
Preferred stock issued and outstanding percentage												30.00%
Conversion basis												40
Preferred stock, outstanding (in shares)																346,045	437,037	346,045	346,045	437,037			346,045
Series A Non-Voting Convertible Preferred Stock \| Minimum
Class Of Stock [Line Items]
Beneficial holders owned percentage												0.00%
Series A Non-Voting Convertible Preferred Stock \| Maximum
Class Of Stock [Line Items]
Beneficial holders owned percentage												19.90%
Series A Non-Voting Convertible Preferred Stock \| Common Stock
Class Of Stock [Line Items]
Conversion of non-voting convertible preferred stock into common stock (in shares)																				25,972,000
Series A Non-Voting Convertible Preferred Stock \| Preferred Stock
Class Of Stock [Line Items]
Issuance of Series A non-voting convertible preferred stock in connection with the asset acquisition of Spyre and settlement of related forward contract (in shares)										364,887										365,000
Conversion of non-voting convertible preferred stock into common stock (in shares)																				(649,000)
Preferred stock, outstanding (in shares)																346,000	437,000	346,000	346,000	437,000				0
Exchange of Series A non-voting convertible preferred stock for common stock (in shares)																			(91,000)
Series A Non-Voting Convertible Preferred Stock \| Preferred Stock \| Conversion of Series A Non-Voting Convertible Preferred Stock
Class Of Stock [Line Items]
Conversion of non-voting convertible preferred stock into common stock (in shares)					90,992												649,302
Private Placement
Class Of Stock [Line Items]
Sale of stock (in shares)											721,452			721,452
Public offering price (in dollars per share) \| $ / shares											$ 291.08
Aggregate purchase price for stock sold \| $								$ 84,600,000			$ 197,300,000
Offering costs \| $						$ 11,200,000		$ 5,400,000			$ 12,700,000
Private Placement \| Series B Non-Voting Convertible Preferred Stock
Class Of Stock [Line Items]
Public offering price (in dollars per share) \| $ / shares						$ 1,480		$ 600.00
Aggregate purchase price for stock sold \| $						$ 168,900,000		$ 169,100,000
Offering costs \| $						$ 11,200,000		$ 10,900,000
Issuance of Series B non-voting convertible preferred stock in connection with private placement, net of financing costs (in shares)						121,625	271,625	150,000
Private Placement \| Series B Non-Voting Convertible Preferred Stock \| Common Stock
Class Of Stock [Line Items]
Sale of stock (in shares)								6,000,000
Public offering price (in dollars per share) \| $ / shares								$ 15.00
At-The-Market Offering
Class Of Stock [Line Items]
Sale of stock, authorized amount \| $																						$ 500,000,000.0
At-The-Market Offering \| Common Stock
Class Of Stock [Line Items]
Sale of stock (in shares)																445,668		445,668	777,432
Public offering price (in dollars per share) \| $ / shares																$ 33.772		$ 33.772	$ 26.935
Aggregate purchase price for stock sold \| $																$ 14,800,000		$ 14,800,000	$ 20,500,000
Offering costs \| $																300,000		300,000	$ 400,000
Sale of stock, authorized amount \| $																					$ 500,000,000.0
Sale of stock, aggregate offering price \| $																					$ 179,100,000	$ 200,000,000.0
Sale of stock, remaining authorized amount available for sale \| $																$ 164,100,000		$ 164,100,000
At-The-Market Offering \| Common Stock \| Subsequent Event
Class Of Stock [Line Items]
Sale of stock (in shares)													296,396
Public offering price (in dollars per share) \| $ / shares													$ 33.566
Aggregate purchase price for stock sold \| $													$ 9,700,000
Offering costs \| $													200,000
Sale of stock, remaining authorized amount available for sale \| $													$ 154,100,000
November 2024 Underwritten Offering \| Common Stock
Class Of Stock [Line Items]
Sale of stock (in shares)			8,366,250
Public offering price (in dollars per share) \| $ / shares			$ 27.50
Aggregate purchase price for stock sold \| $			$ 215,900,000
Offering costs \| $			$ 14,200,000
Over-Allotment Option \| Common Stock
Class Of Stock [Line Items]
Sale of stock (in shares)	2,229,729	1,091,250
October 2025 Underwritten Offering \| Common Stock
Class Of Stock [Line Items]
Sale of stock (in shares)	17,094,594
Public offering price (in dollars per share) \| $ / shares	$ 18.50
Aggregate purchase price for stock sold \| $	$ 296,400,000
Offering costs \| $	$ 19,900,000

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
CURRENT ASSETS
Cash and cash equivalents	$ 85,721	$ 89,423
Marketable securities	670,812	513,665
Prepaid expenses and other current assets	21,248	5,386
Total current assets	777,781	608,474
Other non-current assets	0	10
TOTAL ASSETS	777,781	608,484
CURRENT LIABILITIES
CVR liability	22,820	25,080
Accrued and other current liabilities	26,947	27,711
Total current liabilities	58,685	54,060
Non-current CVR liability	3,860	36,620
TOTAL LIABILITIES	62,545	90,680
Commitments and Contingencies (Note 8, Note 9)
CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY
Common stock, $0.0001 par value; 400,000,000 shares authorized as of December 31, 2025 and December 31, 2024; 78,189,811 shares and 60,257,023 shares issued and outstanding as of December 31, 2025 and December 31, 2024, respectively.	15	13
Additional paid-in capital	1,686,167	1,334,223
Accumulated other comprehensive income	869	180
Accumulated deficit	(1,127,635)	(972,432)
TOTAL CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY	715,236	517,804
TOTAL LIABILITIES, CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY	777,781	608,484
Series A Non-Voting Convertible Preferred Stock
CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY
Preferred stock	146,425	146,425
Series B Non-Voting Convertible Preferred Stock
CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY
Preferred stock	9,395	9,395
Preferred Stock, Excluding Non-Voting Stock
CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY
Preferred stock	0	0
Nonrelated Party
CURRENT LIABILITIES
Accounts payable	8,904	666
Related Party
CURRENT LIABILITIES
Related party accounts payable	$ 14	$ 603

Related Party Transactions

12 Months Ended

Dec. 31, 2025

Related Party Transactions

Paragon and Parapyre each beneficially own less than 5% of a class of the Company's voting securities through their respective holdings of the Company's common stock. Fairmount Funds Management LLC ("Fairmount") beneficially owns more than 5% of a class of the Company's voting securities, has two seats on the Board (held by Peter Harwin and Tomas Kiselak) and beneficially owns more than 5% of Paragon. Fairmount appointed Paragon's board of directors and has the contractual right to approve the appointment of any executive officers of Paragon. Parapyre is an entity formed by Paragon as a vehicle to hold equity in Spyre

in order to share profits with certain employees of Paragon and will not perform any substantive role under the Paragon Agreement other than to receive warrants granted to Parapyre under the Paragon Agreement.


	Year Ended December 31,
	2025		2024		2023
Reimbursable costs under the Paragon Agreement	$	0.1	$	15.3	$	37.1
License Agreements milestone and sublicensing fees	10.4		10.2		—
Total related party expense (excludes stock comp)	$	10.5	$	25.5	$	37.1

The following is the summary of Related party accounts payable and other current liabilities (in millions):


	December 31,
	2025		2024
Reimbursable costs under the Paragon Agreement	$	—	$	0.1
License Agreements development milestone liability (see Note 9)	—		0.5
Total related party accounts payable	$	—	$	0.6

Paragon Agreement

In connection with the Asset Acquisition, the Company assumed the rights and obligations of Pre-Merger Spyre under the Paragon Agreement. Under the Paragon Agreement, Spyre is obligated to compensate Paragon for its services performed under each research program based on the actual costs incurred with mark-up costs pursuant to the terms of the Paragon Agreement. As of the date of the Asset Acquisition, Pre-Merger Spyre had incurred total expenses of $19.0 million under the Paragon Agreement since inception, which included the $3.0 million research initiation fee and $16.0 million of reimbursable expenses under the Paragon Agreement for historical costs owed to Paragon. As of the acquisition date, $19.0 million was unpaid and was assumed by the Company through the Asset Acquisition. The Paragon Agreement was amended and restated on September 29, 2023 and May 14, 2024. Please refer to Note 8 for additional information on the Paragon Agreement.

On July 12, 2023, December 14, 2023, and June 5, 2024, the Company exercised the Option available under the Paragon Agreement with respect to the SPY001, SPY002 and SPY003 research programs, respectively. The Option with respect to one additional program remains unexercised under the Paragon Agreement. Please refer to Note 9 for additional information on the License Agreements related to the exercised options.

On May 14, 2024, the Company, Paragon and Parapyre entered into a second amended and restated antibody discovery and option agreement that amends and restates that certain amended and restated antibody discovery and option agreement, dated September 29, 2023, by and between Paragon, Parapyre and Spyre Therapeutics, LLC, in order to, among other things, (i) replace the Company’s subsidiary with the Company as a party to the agreement and (ii) amend certain terms related to the SPY003 research program, including without limitation, (a) establishing an SPY003 antibody selection process pursuant to which the Company and Paragon shall alternate in turn to select a project antibody to be included and excluded, respectively, from the Company’s rights under its option to license certain intellectual property rights related to SPY003 from Paragon until all project antibodies under the SPY003 research program have been selected; (b) reducing the development costs invoiced to the Company for the SPY003 research program incurred from and after April 1, 2024 through completion of the SPY003 antibody selection process by 50%; (c) requiring Paragon to reimburse the Company for 50% of the development costs for the SPY003 research program incurred prior to April 1, 2024; provided, that Paragon receives rights to at least one SPY003 project antibody following completion of the SPY003 antibody selection process; (d) obligating the Company to exercise its option to license the intellectual property rights to SPY003 project antibodies and technology following the completion of the SPY003 antibody selection

process; and (e) establishing a license agreement term sheet for the SPY003 research program with substantially similar milestone payment terms and royalty payment terms as the SPY001 License Agreement. Please refer to Note 9 for additional disclosures.

For the years ended December 31, 2025, 2024 and 2023, the Company recognized expenses related to services provided by Paragon subsequent to the Asset Acquisition totaling $0.1 million and $29.8 million and $48.5 million, which included nil , $14.5 million and $11.4 million of stock-based compensation expense, respectively, and were recorded as Research and development expenses in the consolidated statements of operations. Included within the expenses recognized for services provided by Paragon for the year ended December 31, 2024, is a $5.9 million reduction in Research and development expenses related to the reimbursement of 50% of the development costs for the SPY003 research program by Paragon.

For the years ended December 31, 2025, 2024 and 2023, the Company made payments totaling $0.2 million and $31.8 million and $39.5 million, respectively, to Paragon.

Parapyre Option Obligation

Pursuant to the Paragon Agreement, the Company issued Parapyre an annual equity grant of warrants, on the last business day of each of the years ended December 31, 2023 and December 31, 2024, to purchase 1% of the then outstanding shares of the Company's common stock, on a fully diluted basis, during the term of the Paragon Agreement. See Note 15 for disclosures related to the Parapyre Option Obligation.

Paragon License Agreements

See Note 9 for disclosures related to the License Agreements entered into with Paragon.

December 2023 PIPE

On December 11, 2023, the Company completed December 2023 PIPE. The December 2023 PIPE Investors included Fairmount, a related party. Fairmount's participation in the December 2023 PIPE was approved by the Company's board of directors. Fairmount's investment accounted for $10.0 million of the $180.0 million gross proceeds raised in the December 2023 PIPE. See Note 1 for disclosures related to the December 2023 PIPE.

Mark McKenna Option Grant

On February 1, 2024, the Board appointed Mark McKenna as a Class I director. Mr. McKenna and the Company are parties to a consulting agreement, pursuant to which Mr. McKenna agreed to continue to provide consulting services as an independent contractor to the Company, with an effective date of August 1, 2023 (the “Vesting Commencement Date”). As compensation for Mr. McKenna’s consulting services, on November 22, 2023, he was granted non-qualified stock options to purchase 477,000 shares of the Company’s common stock under the Company's equity incentive plan with an exercise price of $10.39 per share, which vest as to 25% on the one year anniversary of the Vesting Commencement Date and thereafter vest and become exercisable in 48th equal monthly installments, subject to Mr. McKenna’s continued service to the Company through each applicable vesting date. For the years ended December 31, 2025, 2024 and 2023, the Company recognized $1.0 million, $1.1 million and $0.1 million, respectively, in stock-based compensation expense related to Mr. McKenna's consulting agreement.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-5

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-6

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(g)(3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(e))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/850/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-6

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

+ Details

Accrued and Other Current Liabilities

12 Months Ended

Dec. 31, 2025

Accrued Liabilities and Other Liabilities [Abstract]

Accrued and Other Current Liabilities

Accrued and other current liabilities consist of the following (in thousands):


	December 31,
	2025		2024
Accrued compensation	$	7,940	$	5,688
Accrued contracted research and development costs	17,424		20,861
Accrued professional and consulting fees	1,404		661
Other	179		501
Total accrued and other current liabilities	$	26,947	$	27,711

Audit Information	12 Months Ended
Audit Information	Dec. 31, 2025
Audit Information [Abstract]
Auditor Firm ID	185
Auditor Name	KPMG LLP
Auditor Location	San Diego, California

Novation of Manufacturing Agreements (Details)	1 Months Ended
Novation of Manufacturing Agreements (Details)	Apr. 30, 2023 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Right to terminate agreement or work order, prior written notice period	30 days
Right to terminate work order, reasonable cause, prior written notice period	6 months
Right to terminate work order by counterparty, reasonable cause, termination amount payable	$ 0
Right to terminate work order, material breach, uncured period	30 days
Right to terminate work order, unusual or infrequent cause, period	90 days
Non-refundable license fee amount	$ 200,000
Royalty percentage (less than)	1.00%
Right to terminate agreement, prior written notice period	6 months
Right to terminate agreement by counterparty, material breach, uncured period	60 days
Right to terminate agreement by counterparty, payments not received, period	30 days

Fair Value Measurements - Narrative (Details) - USD ($)			6 Months Ended	12 Months Ended
Fair Value Measurements - Narrative (Details) - USD ($)	Jul. 07, 2023	Jun. 22, 2023	Dec. 31, 2023	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of liability				$ 26,680,000	$ 61,700,000
Forward Contract Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of liability		$ 106,200,000
Change in fair value of derivative liability				0	0	$ 83,530,000
Increase in fair value of derivative			$ 83,500,000
CVR Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in fair value of derivative liability				(29,769,000)	$ 20,430,000	18,986,000
Increase in fair value of derivative				$ (29,769,000)
Series A Non-Voting Convertible Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Issuance of Series A non-voting convertible preferred stock	$ 189,700,000					$ 189,741,000
Spyre Therapeutics, Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset acquisition, cash payment, threshold period		1 year
Spyre Therapeutics, Inc. \| Series A Non-Voting Convertible Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Shares transferred as equity interest in asset acquisition (in shares)		364,887

Cash Equivalents and Marketable Securities - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Cash Equivalents And Marketable Securities [Line Items]
Unrealized gains (losses) on marketable securities	$ 700,000	$ (100,000)	$ (300,000)
Accrued interest receivable on available-for-sale debt securities	$ 4,500,000	$ 3,400,000
Debt Securities, Available-For-Sale, Accrued Interest, After Allowance For Credit Loss, Statement Of Financial Position, Extensible List, Not Disclosed Flag	Accrued interest receivable on available-for-sale debt securities	Accrued interest receivable on available-for-sale debt securities
US Government Agencies Debt Securities
Cash Equivalents And Marketable Securities [Line Items]
Debt securities, available-for-sale, allowance for credit loss, excluding accrued interest	$ 0	$ 0
Impairment of marketable securities	0	0
Realized gains on marketable securities	$ 0	$ 0	$ 0

Defined Contribution Plan (Details) - USD ($) $ in Millions	12 Months Ended
Defined Contribution Plan (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Retirement Benefits [Abstract]
Defined contribution plan, contribution amount	$ 0.8	$ 0.5	$ 0.2

The Company and Basis of Presentation (Details) $ / shares in Units, $ in Thousands												1 Months Ended		3 Months Ended			12 Months Ended			130 Months Ended
	Oct. 15, 2025 USD ($) $ / shares shares	Nov. 29, 2024 shares	Nov. 20, 2024 USD ($) $ / shares shares	May 14, 2024 shares	Apr. 23, 2024 shares	Mar. 20, 2024 USD ($) $ / shares shares	Mar. 18, 2024 shares	Dec. 11, 2023 USD ($) $ / shares shares	Sep. 08, 2023	Jun. 26, 2023 USD ($) $ / shares shares	Jun. 22, 2023 $ / shares shares	Feb. 12, 2026 USD ($) $ / shares shares	Jun. 30, 2023 shares	Dec. 31, 2025 USD ($) $ / shares shares	Dec. 31, 2023 shares	Jun. 30, 2023	Dec. 31, 2025 USD ($) segment $ / shares shares	Dec. 31, 2024 USD ($) $ / shares shares	Dec. 31, 2023 shares	Dec. 31, 2025 USD ($) $ / shares shares	Feb. 28, 2025 USD ($)	Sep. 06, 2024 USD ($)	Apr. 25, 2024 shares	Dec. 08, 2023	Dec. 31, 2022 shares
Company and Basis of Presentation [Line Items]
Number of operating segments \| segment																	1
Employee workforce, termination percentage																83.00%
Convertible preferred stock, par value (in dollars per share) \| $ / shares														$ 0.0001			$ 0.0001			$ 0.0001
Issuance of Series B non-voting convertible preferred stock in connection with private placement, net of financing costs (in shares)								150,000
Proceeds from raising capital \| $																				$ 1,600,000
Accumulated deficit \| $														$ 1,127,635			$ 1,127,635	$ 972,432		1,127,635
Cash, cash equivalents, and marketable securities \| $														$ 756,500			$ 756,500			$ 756,500
Private Placement
Company and Basis of Presentation [Line Items]
Sale of stock (in shares)										721,452			721,452
Public offering price (in dollars per share) \| $ / shares										$ 291.08
Aggregate purchase price for stock sold \| $								$ 84,600		$ 197,300
Offering costs \| $						$ 11,200		$ 5,400		$ 12,700
At-The-Market Offering
Company and Basis of Presentation [Line Items]
Sale of stock, authorized amount \| $																						$ 500,000
Series A Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Convertible preferred stock, par value (in dollars per share) \| $ / shares														$ 0.0001			$ 0.0001	$ 0.0001		$ 0.0001
Conversion basis											40
Preferred stock, outstanding (in shares)														346,045	437,037		346,045	346,045	437,037	346,045			346,045
Series B Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Convertible preferred stock, par value (in dollars per share) \| $ / shares														$ 0.0001			$ 0.0001	$ 0.0001		$ 0.0001
Conversion basis						40		40																40
Series B non-voting convertible preferred stock, par value (in dollars per share) \| $ / shares								$ 0.0001
Issuance of Series B non-voting convertible preferred stock in connection with private placement, net of financing costs (in shares)						121,625	271,625	150,000
Preferred stock, outstanding (in shares)														16,667			16,667	16,667		16,667
Preferred stock, not automatically converted, outstanding (in shares)														16,667			16,667			16,667
Series B Non-Voting Convertible Preferred Stock \| Private Placement
Company and Basis of Presentation [Line Items]
Public offering price (in dollars per share) \| $ / shares						$ 1,480		$ 600.00
Aggregate purchase price for stock sold \| $						$ 168,900		$ 169,100
Offering costs \| $						$ 11,200		$ 10,900
Issuance of Series B non-voting convertible preferred stock in connection with private placement, net of financing costs (in shares)						121,625	271,625	150,000
Common Stock
Company and Basis of Presentation [Line Items]
Exchange of Series A non-voting convertible preferred stock for common stock (in shares)					3,639,680
Common Stock \| At-The-Market Offering
Company and Basis of Presentation [Line Items]
Sale of stock (in shares)														445,668			445,668	777,432
Public offering price (in dollars per share) \| $ / shares														$ 33.772			$ 33.772	$ 26.935		$ 33.772
Aggregate purchase price for stock sold \| $														$ 14,800			$ 14,800	$ 20,500
Offering costs \| $														300			300	$ 400
Sale of stock, authorized amount \| $																					$ 500,000
Sale of stock, aggregate offering price \| $																					$ 179,100	$ 200,000
Sale of stock, remaining authorized amount available for sale \| $														$ 164,100			$ 164,100			$ 164,100
Common Stock \| At-The-Market Offering \| Subsequent Event
Company and Basis of Presentation [Line Items]
Sale of stock (in shares)												296,396
Public offering price (in dollars per share) \| $ / shares												$ 33.566
Aggregate purchase price for stock sold \| $												$ 9,700
Offering costs \| $												200
Sale of stock, remaining authorized amount available for sale \| $												$ 154,100
Common Stock \| November 2024 Underwritten Offering
Company and Basis of Presentation [Line Items]
Sale of stock (in shares)			8,366,250
Public offering price (in dollars per share) \| $ / shares			$ 27.50
Aggregate purchase price for stock sold \| $			$ 215,900
Offering costs \| $			$ 14,200
Common Stock \| Over-Allotment Option
Company and Basis of Presentation [Line Items]
Sale of stock (in shares)	2,229,729	1,091,250
Common Stock \| October 2025 Underwritten Offering
Company and Basis of Presentation [Line Items]
Sale of stock (in shares)	17,094,594
Public offering price (in dollars per share) \| $ / shares	$ 18.50
Aggregate purchase price for stock sold \| $	$ 296,400
Offering costs \| $	$ 19,900
Common Stock
Company and Basis of Presentation [Line Items]
Reverse stock split, conversion ratio									0.04
Conversion of non-voting convertible preferred stock into common stock (in shares)																		10,198,000
Exchange of Series A non-voting convertible preferred stock for common stock (in shares)																		3,640,000
Common Stock \| Conversion of Series A Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Conversion of non-voting convertible preferred stock into common stock (in shares)															25,972,080
Common Stock \| Conversion of Series B Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Conversion of non-voting convertible preferred stock into common stock (in shares)				10,198,320														10,198,320
Common Stock \| Series A Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Conversion of non-voting convertible preferred stock into common stock (in shares)																			25,972,000
Common Stock \| Series B Non-Voting Convertible Preferred Stock \| Private Placement
Company and Basis of Presentation [Line Items]
Sale of stock (in shares)								6,000,000
Public offering price (in dollars per share) \| $ / shares								$ 15.00
Preferred Stock \| Series A Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Conversion of non-voting convertible preferred stock into common stock (in shares)																			(649,000)
Exchange of Series A non-voting convertible preferred stock for common stock (in shares)																		(91,000)
Preferred stock, outstanding (in shares)														346,000	437,000		346,000	346,000	437,000	346,000					0
Preferred Stock \| Series A Non-Voting Convertible Preferred Stock \| Conversion of Series A Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Conversion of non-voting convertible preferred stock into common stock (in shares)					90,992										649,302
Preferred Stock \| Series B Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Issuance of Series B non-voting convertible preferred stock in connection with private placement, net of financing costs (in shares)																		122,000	150,000
Conversion of non-voting convertible preferred stock into common stock (in shares)																		(255,000)
Preferred stock, outstanding (in shares)														17,000	0		17,000	17,000	0	17,000					0
Preferred Stock \| Series B Non-Voting Convertible Preferred Stock \| Conversion of Series B Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Conversion of non-voting convertible preferred stock into common stock (in shares)				254,958														254,958
Spyre Therapeutics, Inc.
Company and Basis of Presentation [Line Items]
Fixed exchange ratio											0.5494488
Asset acquisition, cash payment, threshold period											1 year
Spyre Therapeutics, Inc. \| Spyre 2023 Equity Incentive Plan
Company and Basis of Presentation [Line Items]
Number of outstanding and unexercised stock options to purchase (in shares)											2,734
Spyre Therapeutics, Inc. \| Series A Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Shares transferred as equity interest in asset acquisition (in shares)											364,887
Convertible preferred stock, par value (in dollars per share) \| $ / shares											$ 0.0001
Conversion basis											40
Spyre Therapeutics, Inc. \| Common Stock
Company and Basis of Presentation [Line Items]
Shares transferred as equity interest in asset acquisition (in shares)											517,809

Fair Value Measurements

12 Months Ended

Dec. 31, 2025

Fair Value Disclosures [Abstract]

Fair Value Measurements

The Company measures and reports certain financial instruments as assets and liabilities at fair value on a recurring basis. The following tables set forth the fair value of the Company’s financial assets and liabilities at fair value on a recurring basis based on the three-tier fair value hierarchy (in thousands):


	December 31, 2025
	Level 1		Level 2		Level 3		Total
Financial Assets
Money market funds	$	74,004	$	—	$	—	$	74,004
U.S. government treasury securities	266,064		—		—		266,064
U.S. government agency securities	—		119,590		—		119,590
Commercial paper	—		194,355		—		194,355
Corporate bonds	—		100,790		—		100,790
Total financial assets	$	340,068	$	414,735	$	—	$	754,803

Liabilities:
CVR liability	$	—	$	—	$	26,680	$	26,680
Total liabilities	$	—	$	—	$	26,680	$	26,680


	December 31, 2024
	Level 1		Level 2		Level 3		Total
Financial Assets
Money market funds	$	65,902	$	—	$	—	$	65,902
U.S. government treasury securities	227,244		—		—		227,244
U.S. government agency securities	—		86,681		—		86,681
Commercial paper	—		165,130		—		165,130
Corporate bonds	—		56,448		—		56,448
Total financial assets	$	293,146	$	308,259	$	—	$	601,405

Liabilities:
CVR liability	$	—	$	—	$	61,700	$	61,700
Total liabilities	$	—	$	—	$	61,700	$	61,700

The Company measures the fair value of money market funds and U.S. government treasury securities on quoted prices in active markets for identical asset or liabilities. The Level 2 assets include U.S. government agency securities, commercial paper and corporate bonds, and are valued based on quoted prices for similar assets in active markets and inputs other than quoted prices that are derived from observable market data.

The Company evaluates transfers in and out of Level 3 at the end of each reporting period. There were no transfers in or out of Level 3 during the periods presented.

As of December 31, 2025 and 2024, the Company had $26.7 million and $61.7 million, respectively, of financial liabilities outstanding measured at fair value.

Forward Contract Liability

In connection with the Asset Acquisition, the Company entered into a contract for the issuance of 364,887 shares of Series A Preferred Stock as part of the consideration transferred. This forward contract was classified as a liability because the underlying preferred shares were contingently redeemable. Further, the forward contract liability was considered a Level 2 liability based on observable market data for substantially the full term of the liability and was initially measured at its estimated fair value on the transaction date based on the underlying price per share on an as-converted basis of the June 2023 PIPE Securities issued in the June 2023 PIPE. Subsequent remeasurement of the fair value of the forward contract liability through its settlement date was based on the market price of the Company's common stock, which represents the redemption value of the Series A Preferred Stock.

The fair value of the forward contract at the transaction date, June 22, 2023, was $106.2 million. The liability was settled with the issuance of the Series A Preferred Stock on July 7, 2023 for $189.7 million. For the year ended December 31, 2023, $83.5 million was recorded as Other income (expense) in the consolidated statements of operations in connection with the change in fair value of the forward contract liability. There was no similar expense for the year ended December 31, 2025 and 2024.

The following table presents changes in the forward contract liability for the periods presented (in millions):


	Forward Contract Liability
Beginning balance as of June 22, 2023	$	106.2
Change in fair value	83.5
Issuance of Series A Preferred Stock on July 7, 2023	(189.7)
Ending balance as of December 31, 2023	$	—

CVR Liability

In connection with the Asset Acquisition, a non-transferable contingent value right was distributed to the Legacy Stockholders, but was not distributed to holders of shares of the Company's common stock or Series A Preferred Stock issued to the June 2023 Investors or former stockholders of Pre-Merger Spyre in connection with the June 2023 Transactions. Holders of the CVRs will be entitled to receive certain cash payments from proceeds received by the Company prior to the third anniversary of the CVR Agreement, if any, related to the disposition or monetization of the Company’s legacy assets during the one-year period following the closing of the Asset Acquisition.

The fair value of the CVR liability was determined using the probability weighted discounted cash flow method to estimate future cash flows associated with the sale of the legacy assets. Analogous to a dividend being declared/approved in one period and paid out in another, the liability was recorded at the date of approval, June 22, 2023, as a common stock dividend, returning capital to the Legacy Stockholders. Changes in fair value of the liability will be recognized as a component of Other income (expense) in the consolidated statement of operations and comprehensive loss in each reporting period. The liability value is based on significant inputs not observable in the market such as estimated cash flows, estimated probabilities of regulatory success, and

discount rates, which represent a Level 3 measurement within the fair value hierarchy. The significant inputs used to estimate the fair value of the CVR liability were as follows:


			December 31, 2025
Estimated cash flow dates			05/15/26 - 08/15/29
Estimated probability of success			0% - 72%
Estimated reimbursement rate compared to reimbursement target			45% - 55%
Risk-adjusted discount rates			9.85% - 9.97%

The change in fair value between December 31, 2024 and December 31, 2025 was a $29.8 million decrease, primarily driven by changes in the likelihood of achievement of certain milestones and receipt of certain cash consideration within the CVR term, changes in estimated reimbursement rates compared to reimbursement target rates, changes in estimated cash flow dates, and an increase in risk-adjusted discount rates, partially offset by time value of money adjustments.

The following table presents changes in the CVR liability for the periods presented (in thousands):


	CVR Liability
Beginning balance as of December 31, 2024	$	61,700

Changes in the fair value of the CVR liability	(29,769)
Payments	(5,251)
Ending Balance as of December 31, 2025	$	26,680

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 107
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-107

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 940
-SubTopic 820
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478119/940-820-50-1

+ Details

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
Consolidated Statements of Cash Flows - USD ($)	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (155,203,000)	$ (208,018,000)	$ (338,790,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	0	0	744,000
Stock-based compensation	37,614,000	44,833,000	25,675,000
Acquired in-process research and development	0	0	130,188,000
Gain on sale of in-process research and development asset	(10,000,000)	0	(16,449,000)
Lease ROU asset and leasehold improvement impairment loss	0	0	2,580,000
Loss on disposal of long-lived assets	0	0	915,000
Net (accretion of discount) amortization of premium on marketable securities	(8,090,000)	(11,404,000)	(2,318,000)
Interest proceeds from maturities of zero coupon debt securities	2,130,000	1,283,000	0
Amortization of operating lease assets	0	0	220,000
Other	0	0	15,000
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(12,819,000)	(2,932,000)	3,245,000
Accounts payable	8,238,000	(230,000)	218,000
Deferred revenue	0	0	575,000
Development receivables	0	0	375,000
Operating lease liabilities	0	0	(2,326,000)
Accrued and other liabilities	(764,000)	14,609,000	(4,891,000)
Related party accounts payable	(589,000)	(15,981,000)	(2,402,000)
Net cash used in operating activities	(169,252,000)	(157,410,000)	(99,910,000)
CASH FLOWS FROM INVESTING ACTIVITIES
Cash assumed from asset acquisition of Spyre	0	0	3,035,000
Proceeds from sale of in-process research & development asset	7,000,000	0	15,000,000
Proceeds from the sale of property plant and equipment	0	0	475,000
Purchases of marketable securities	(522,214,000)	(599,252,000)	(166,803,000)
Proceeds from maturities and sales of marketable securities	371,739,000	245,967,000	39,900,000
Net cash (used in) provided by investing activities	(143,475,000)	(353,285,000)	(108,393,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of common stock in connection with at-the-market offering program, net of issuance costs	14,750,000	20,521,000	0
Proceeds from issuance of common stock in connection with follow-on offering, net of issuance costs	296,382,000	215,860,000	0
Payment of deferred offering costs in connection with shelf registration	(162,000)	(407,000)	0
Payment of contingent value rights liability	(5,251,000)	(1,430,000)	(5,786,000)
Proceeds from employee stock option exercises and employee stock plan purchases	3,306,000	7,511,000	405,000
Other financing cash flows	0	1,000	(16,000)
Net cash provided by financing activities	309,025,000	410,906,000	361,077,000
Effect of exchange rate on cash, cash equivalents, and restricted cash	0	(3,000)	25,000
NET (DECREASE) INCREASE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	(3,702,000)	(99,792,000)	152,799,000
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH
Beginning of period	89,423,000	189,215,000	36,416,000
End of period	85,721,000	89,423,000	189,215,000
Supplemental Disclosure of Non-Cash Investing and Financing Information:
Allocation of deferred offering costs against proceeds of issuance of common stock	107,000	204,000	0
Settlement of forward contract liability and issuance of Series A non-voting convertible preferred stock in connection with the asset acquisition of Spyre	0	0	189,741,000
Reconciliation of Cash, Cash Equivalents, and Restricted Cash Reported in the Statement of Financial Position
Cash and cash equivalents	85,721,000	89,423,000	188,893,000
Restricted cash	0	0	322,000
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	85,721,000	89,423,000	189,215,000
Series B Non-Voting Convertible Preferred Stock
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	(1,317,000)	(10,839,000)	(4,749,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of private placement, net	0	168,850,000	84,555,000
Supplemental Disclosure of Non-Cash Investing and Financing Information:
Conversion of non-voting convertible preferred stock into common stock	0	244,010,000	0
Series A Non-Voting Convertible Preferred Stock
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	(27,344,000)	(47,624,000)	(239,158,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of private placement, net	0	0	197,364,000
Supplemental Disclosure of Non-Cash Investing and Financing Information:
Exchange of Series A non-voting convertible preferred stock for common stock	0	38,502,000	0
Conversion of non-voting convertible preferred stock into common stock	0	0	202,178,000
Common Stock
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	(126,541,000)	(149,555,000)	(94,883,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of private placement, net	0	0	84,555,000
CVR Liability
Adjustments to reconcile net loss to net cash used in operating activities:
Change in fair value of derivative liability	(29,769,000)	20,430,000	18,986,000
Forward Contract Liability
Adjustments to reconcile net loss to net cash used in operating activities:
Change in fair value of derivative liability	$ 0	$ 0	$ 83,530,000

Stock-Based Compensation - Schedule of Weighted-Average Assumptions Used in Calculating Fair Value of Awards (Details)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Dividend yield	0.00%	0.00%	0.00%
Stock Options Granted
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Expected term (in years)	5 years 11 months 26 days	6 years 10 days	5 years 10 months 17 days
Expected volatility	76.00%	105.00%	107.00%
Risk-free interest	4.33%	4.06%	4.37%
Dividend yield	0.00%	0.00%	0.00%
2016 ESPP
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Expected term (in years)	5 months 8 days	6 months	5 months 26 days
Expected volatility	70.00%	84.00%	181.00%
Risk-free interest	4.22%	5.16%	4.99%
Dividend yield	0.00%	0.00%	0.00%

Convertible Preferred Stock and Stockholders’ Equity	12 Months Ended
Convertible Preferred Stock and Stockholders’ Equity	Dec. 31, 2025
Equity [Abstract]
Convertible Preferred Stock and Stockholders’ Equity	Convertible Preferred Stock and Stockholders’ Equity The Company is authorized to issue 410,000,000 shares of capital stock of which 400,000,000 shares are designated as common stock and 10,000,000 shares are designated as preferred stock, all with a par value of $0.0001 per share. Each holder of common stock is entitled to one vote for each share of common stock held. The common stock is not entitled to preemptive rights, and is not subject to conversion, redemption or sinking fund provisions. Subject to preferences that may apply to any shares of preferred stock outstanding at the time, the holders of common stock are entitled to receive dividends out of funds legally available if the board of directors, in its discretion, determines to issue dividends and then only at the times and in the amounts that the board of directors may determine. As of December 31, 2025 and 2024, no common stock dividends had been declared by the board of directors. June 2023 PIPE In June 2023, in connection with the Asset Acquisition, the Company issued and sold 721,452 shares of Series A Preferred Stock at $291.08 per share through a private placement to a group of accredited investors. The net proceeds from this offering were approximately $197.3 million, after deducting placement agent fees and offering costs of $12.7 million. December 2023 PIPE In December 2023, the Company issued and sold 6,000,000 shares of common stock at an offering price of $15.00 per share and 150,000 shares of Series B Preferred Stock at $600 per share through a private placement to a group of accredited investors. The net proceeds from this offering were approximately $169.1 million, after deducting placement agent fees and offering costs of $10.9 million. March 2024 PIPE On March 18, 2024, in connection with the March 2024 PIPE, the Company filed a certificate of amendment to its Series B Certificate of Designation to increase the number of authorized shares of Series B Preferred Stock from 150,000 to 271,625. On March 20, 2024, as part of the March 2024 PIPE, the Company completed a private placement of 121,625 shares of Series B Preferred Stock at an offering price of $1,480 per share. The net proceeds from this offering were approximately $168.9 million, after deducting placement agent fees and offering costs of $11.2 million. September 2024 ATM Facility On September 6, 2024, the Company filed a new shelf registration statement on Form S-3 that was declared effective by the SEC for the potential offering, issuance and sale by the Company of up to $500.0 million of the Company's common stock, preferred stock, debt securities, warrants and/or units consisting of all or some of these securities. Concurrent with the filing of the shelf-registration statement, the Company entered into the Sales Agreement, pursuant to which the Company may issue and sell shares of its common stock for an aggregate offering price of up to $200.0 million under an ATM offering program included in the shelf registration. During the twelve months ended December 31, 2024, the Company sold an aggregate of 777,432 shares of common stock under the ATM offering program at an average price per share of $26.935 resulting in net proceeds of $20.5 million, after deducting sales agent commissions and other offering costs of $0.4 million. During the three and twelve months ended December 31, 2025, the Company sold an aggregate of 445,668 shares of common stock under the ATM offering program at an average price per share of $33.772 resulting in net proceeds of $14.8 million, after deducting sales agent commissions and other offering costs of $0.3 million. As of February 12, 2026, $154.1 million remained available for sale under the Sales Agreement. November 2024 Underwritten Offering On November 18, 2024, the Company entered into the November 2024 Underwriting Agreement with the November 2024 Underwriters, pursuant to which the Company sold an aggregate of 8,366,250 shares of common stock, inclusive of 1,091,250 shares pursuant to the full exercise of the underwriters' over-allotment option, at a public offering price per share of $27.50, resulting in net proceeds of approximately $215.9 million after deducting approximately $14.2 million of underwriting discounts and other offering costs. The November 2024 Offering closed on November 20, 2024 and the over-allotment option was exercised in full on November 26, 2024 and closed on November 29, 2024. October 2025 Underwritten Offering On October 13, 2025, the Company entered into the October 2025 Underwriting Agreement with the October 2025 Underwriters, pursuant to which the Company sold an aggregate of 17,094,594 shares of common stock, inclusive of 2,229,729 shares pursuant to the full exercise of the underwriters' over-allotment option, at a public offering price per share of $18.50, resulting in net proceeds of approximately $296.4 million after deducting approximately $19.9 million of underwriting discounts and other offering costs. The over-allotment option was exercised in full on October 14, 2025 and the transaction closed on October 15, 2025. Parapyre Warrants The Company settled its 2024 and 2023 obligations under the Parapyre Option Obligation by issuing Parapyre 848,184 and 684,407 warrants, respectively, to purchase the Company's common stock, at an exercise price per share per warrant of $23.28 and $21.52, respectively. As of December 31, 2025, none of the warrants issued under the Parapyre Option Obligation have been exercised. See Note 15 for additional information on the Parapyre Option Obligation. Pre-Funded Warrants In May 2022, the Company issued pre-funded warrants to purchase shares of its common stock in underwritten public offerings at the offering price of the common stock, less the $0.0025 per share exercise price of each warrant. The warrants were recorded as a component of stockholders’ equity within additional paid-in capital and have no expiration date. Per the terms of the warrant agreements, the outstanding warrants to purchase shares of the Company's common stock may not be exercised if the holder’s ownership of the Company's common stock would exceed 4.99% (“Maximum Ownership Percentage”) or 9.99% for certain holders. By written notice to the Company, each holder may increase or decrease the Maximum Ownership Percentage to any other percentage (not in excess of 19.90% for the majority of such warrants). The revised Maximum Ownership Percentage would be effective 61 days after the notice is received by the Company. As of December 31, 2025, all pre-funded warrants have been exercised and none remain outstanding. Series A Non-Voting Convertible Preferred Stock On June 22, 2023, the Company filed a Certificate of Designation of Preferences, Rights and Limitations of the Series A Preferred Stock with the Secretary of State of the State of Delaware (the “Series A Certificate of Designation”) in connection with the Asset Acquisition and the June 2023 PIPE. Pursuant to the Series A Certificate of Designation, holders of Series A Preferred Stock are entitled to receive dividends on shares of Series A Preferred Stock equal to, on an as-if-converted-to-common stock basis, and in the same form as, dividends actually paid on shares of the Company's common stock. Except as provided in the Series A Certificate of Designation or as otherwise required by law, the Series A Preferred Stock does not have voting rights. However, as long as any shares of Series A Preferred Stock are outstanding, the Company will not, without the affirmative vote of the holders of a majority of the then outstanding shares of the Series A Preferred Stock: (a) alter or change adversely the powers, preferences or rights given to the Series A Preferred Stock, or alter or amend the Series A Certificate of Designation, amend or repeal any provision of, or add any provision to, the Company’s Certificate of Incorporation or its Bylaws, or file any articles of amendment, certificate of designations, preferences, limitations and relative rights of any series of preferred stock, if such action would adversely alter or change the preferences, rights, privileges or powers of, or restrictions provided for the benefit of the Series A Preferred Stock, regardless of whether any of the foregoing actions will be by means of amendment to the Certificate of Incorporation or by merger, consolidation, recapitalization, reclassification, conversion or otherwise, (b) issue further shares of Series A Preferred Stock or increase or decrease (other than by conversion) the number of authorized shares of Series A Preferred Stock, (c) prior to the stockholder approval of the conversion of the Series A Preferred Stock into shares of common stock in accordance with Nasdaq Stock Market Rules (the “Series A Conversion Proposal”) or at any time while at least 30% of the originally issued Series A Preferred Stock remains issued and outstanding, consummate (x) any Fundamental Transaction (as defined in the Series A Certificate of Designation) or (y) any merger or consolidation of the Company with or into another entity or any stock sale to, or other business combination in which our stockholders immediately before such transaction do not hold at least a majority of our capital stock immediately after such transaction or (d) enter into any agreement with respect to any of the foregoing. The Series A Preferred Stock does not have a preference upon any liquidation, dissolution or winding-up of the Company. The Company held a stockholders’ meeting to submit the following matters to its stockholders for their consideration: (i) the approval of the Series A Conversion Proposal, and (ii) if deemed necessary or appropriate by the Company or as otherwise required by law or contract, the approval of an amendment to the Certificate of Incorporation to authorize sufficient shares of common stock for the conversion of the Series A Preferred Stock issued pursuant to the Acquisition Agreement. In connection with these matters, the Company filed with the SEC a definitive proxy statement and other relevant materials. On June 26, 2023, the Company completed a private placement of 721,452 shares of June 2023 PIPE Securities at $291.08 per share in exchange for net proceeds of $197.3 million after deducting placement agent fees and offering costs of $12.7 million. On July 7, 2023, the Company issued 364,887 shares of Series A Preferred Stock as part of its consideration transferred in connection with the Asset Acquisition that closed on June 22, 2023 which settled the related forward contract liability. For additional information, see Note 3. On November 21, 2023, the Company's stockholders approved the Series A Conversion Proposal, among other matters, at a special meeting of stockholders. As a result of the approval of the Series A Conversion Proposal, all conditions that could have required cash redemption of the Series A Preferred Stock were satisfied. Since the Series A Preferred Stock is no longer redeemable, the associated balances of the Series A Preferred Stock were reclassified from mezzanine equity to permanent equity during the fourth quarter of 2023. Following stockholder approval of the Series A Conversion Proposal, each share of Series A Preferred Stock automatically converted into 40 shares of the Company's common stock, subject to certain limitations, including that a holder of Series A Preferred Stock is prohibited from converting shares of Series A Preferred Stock into shares of common stock if, as a result of such conversion, such holder, together with its affiliates, would beneficially own more than a specified percentage (established by the holder between 0.0% and 19.9%) of the total number of shares of common stock issued and outstanding immediately after giving effect to such conversion. 649,302 shares of Series A Preferred Stock automatically converted to 25,972,080 shares of common stock; 437,037 shares of Series A Preferred Stock did not automatically convert and remained outstanding following the conversion. This conversion was recorded as a reclassification between Series A Preferred Stock and common stock based on the historical per-share contributed capital amount of the Series A Preferred Stock. On April 23, 2024, in connection with the April 2024 Exchange, the Stockholder agreed to exchange an aggregate of 90,992 shares of Series A Preferred Stock for an aggregate of 3,639,680 shares of the Company's common stock. This exchange was recorded as a reclassification between Series A Preferred Stock and common stock based on the historical per-share contributed capital amount, inclusive of any forward-contract valuation adjustments, of the Series A Preferred Stock. The April 2024 Exchange closed on April 25, 2024, with 346,045 shares of Series A Preferred Stock remaining outstanding following closing. Series B Non-Voting Convertible Preferred Stock On December 8, 2023, the Company filed a Certificate of Designation of Preferences, Rights and Limitations of Series B Non-Voting Convertible Preferred Stock with the Secretary of State of the State of Delaware (the “Series B Certificate of Designation”) in connection with the December 2023 PIPE. Pursuant to the Series B Certificate of Designation, holders of Series B Preferred Stock are entitled to receive dividends on shares of Series B Preferred Stock equal to, on an as-if-converted-to-common stock basis, and in the same form as, dividends actually paid on shares of Company common stock. Except as provided in the Series B Certificate of Designation or as otherwise required by law, the Series B Preferred Stock does not have voting rights. However, as long as any shares of Series B Preferred Stock are outstanding, the Company will not, without the affirmative vote of the holders of a majority of the then outstanding shares of the Series B Preferred Stock, alter or change adversely the powers, preferences or rights given to the Series B Preferred Stock, or alter or amend the Series B Certificate of Designation, amend or repeal any provision of, or add any provision to, the Company’s Certificate of Incorporation or its Bylaws, or file any articles of amendment, certificate of designations, preferences, limitations and relative rights of any series of preferred stock, if such action would adversely alter or change the preferences, rights, privileges or powers of, or restrictions provided for the benefit of the Series B Preferred Stock, regardless of whether any of the foregoing actions will be by means of amendment to the Certificate of Incorporation or by merger, consolidation, recapitalization, reclassification, conversion or otherwise. The Series B Preferred Stock does not have a preference upon any liquidation, dissolution or winding-up of the Company. On December 11, 2023, as part of the December 2023 PIPE, the Company completed a private placement of 150,000 shares of Series B Preferred Stock at $600 per share in exchange for net proceeds of $84.6 million after deducting placement and offering costs of $5.4 million. On March 18, 2024, in connection with the March 2024 PIPE, the Company filed a certificate of amendment to its Series B Certificate of Designation to increase the number of authorized shares of Series B Preferred Stock from 150,000 to 271,625. On March 20, 2024, as part of the March 2024 PIPE, the Company completed a private placement of 121,625 shares of Series B Preferred Stock at $1,480 per share in exchange for net proceeds of approximately $168.9 million, after deducting placement agent fees and offering costs of $11.2 million. On May 14, 2024, the Company's stockholders approved the issuance of Company common stock upon the conversion of all issued and outstanding Series B Preferred Stock into shares of common stock in accordance with the Nasdaq Stock Market Rules (the "Series B Conversion Proposal"), among other matters, at its 2024 annual meeting of stockholders. As a result of the approval of the Series B Conversion Proposal, all conditions that could have required cash redemption of the Series B Preferred Stock were satisfied. Since the Series B Preferred Stock were no longer redeemable, the associated balances of the Series B Preferred Stock were reclassified from mezzanine equity to permanent equity during the second quarter of 2024. A total of 254,958 shares of Series B Preferred Stock automatically converted to 10,198,320 shares of common stock; 16,667 shares of Series B Preferred Stock did not automatically convert and remained outstanding as of December 31, 2025. Following stockholder approval of the Series B Conversion Proposal, each share of Series B Preferred Stock will automatically convert into 40 shares of the Company's common stock, subject to certain limitations, including that a holder of Series B Preferred Stock is prohibited from converting shares of Series B Preferred Stock into shares of common stock if, as a result of such conversion, such holder, together with its affiliates, would beneficially own more than a specified percentage (established by the holder between 0% and 19.9%) of the total number of shares of common stock issued and outstanding immediately after giving effect to such conversion. 254,958 shares of Series B Preferred Stock automatically converted to 10,198,320 shares of common stock; 16,667 shares of Series B Preferred Stock did not automatically convert and remain outstanding as of December 31, 2025 due to beneficial ownership limitations. This conversion was recorded as a reclassification between Series B Preferred Stock and common stock based on the historical per-share contributed capital amount of the Series B Preferred Stock.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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+ Details

Segment Reporting (Tables)

12 Months Ended

Dec. 31, 2025

Segment Reporting [Abstract]

Schedule of Significant Expenses Provided to the CODM on a Regular Basis

The following table sets forth the significant expenses provided to the CODM on a regular basis (in thousands):


	Year Ended December 31,
	2025		2024		2023
Revenue	$	—	$	—	$	886

Less:
Compensation	$	34,794	$	21,780	$	22,590
Stock-based compensation (1)	37,614		44,833		25,675
Research and development, excluding compensation and stock-based compensation (2) (3)	132,490		127,491		65,282
Other segment items (4) (5)	(49,695)		13,914		226,129
Segment net loss	$	155,203	$	208,018	$	338,790

Reconciliation of net loss
Adjustments and reconciling items	—		—		—
Consolidated net loss	$	155,203	$	208,018	$	338,790

(1)Includes $1.0 million, $15.6 million and $11.5 million in related party expenses for the years ended December 31, 2025, 2024 and 2023, respectively.

(2)Includes non-clinical study expenses, clinical trial expenses and manufacturing costs.

(3)Includes $10.5 million, $25.5 million and $37.1 million in related party expenses for the years ended December 31, 2025, 2024 and 2023, respectively.

(5)Includes a $29.8 million decrease, a $20.4 million increase and a $18.9 million increase in fair value of CVR liability for the years ended December 31, 2025, 2024 and 2023, respectively.

Summary of Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2025 USD ($) bank	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Cash Equivalents And Marketable Securities [Line Items]
Restricted cash	$ 0	$ 0
Number of domestic banking institutions (in banks) \| bank	2
Impairments of long-lived assets	$ 0	0	$ 2,600,000
Impairment, Long-Lived Asset, Held-for-Use, Statement of Income or Comprehensive Income [Extensible Enumeration]			Research and development
Operating and finance lease obligations	0	0
Unrecognized tax benefits	0	0
Interest or penalties incurred	0	0	$ 0
Maximum \| U.S. Banking Institution
Cash Equivalents And Marketable Securities [Line Items]
Cash, FDIC insured amount	$ 250,000	$ 250,000

Stock-Based Compensation - Narrative (Details)		1 Months Ended							12 Months Ended
Stock-Based Compensation - Narrative (Details)	Sep. 29, 2023 grant	Jan. 31, 2024 shares	Nov. 30, 2023 USD ($) shares	Feb. 28, 2023 shares	Oct. 31, 2018 shares	Jun. 30, 2018	Feb. 28, 2018 shares	Apr. 30, 2016 USD ($) shares	Dec. 31, 2025 USD ($) $ / shares shares	Dec. 31, 2024 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) $ / shares shares	Jan. 01, 2025 shares	Jan. 01, 2024 shares	Jun. 22, 2023 shares	Jan. 01, 2023 shares	May 31, 2022 $ / shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding option awards (in shares)									11,370,247	9,253,158
Exercise price per warrant (in dollars per share) \| $ / shares																$ 0.0025
Stock-based compensation \| $									$ 37,614,000	$ 44,833,000	$ 25,675,000
Tax benefits recognized \| $									$ 0	$ 0	$ 0
Dividend yield									0.00%	0.00%	0.00%
Non- Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense \| $									$ 1,026,000	$ 15,888,000	$ 11,438,000
Parapyre Option Obligation
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of annual grant of common stock outstanding for warrants														1.00%
Warrants term	10 years
Number of separate grants \| grant	2
Stock-based compensation \| $									$ 0
Parapyre Warrants
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrants to purchase shares (in shares)										848,184	684,407
Exercise price per warrant (in dollars per share) \| $ / shares										$ 23.28	$ 21.52
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value (in dollars per share) \| $ / shares									$ 19.98	$ 28.39	$ 9.67
Intrinsic value of options exercised \| $									$ 4,000,000.0	$ 22,700,000	$ 400,000
Unrecognized stock-based compensation expense for options \| $									$ 81,300,000
Weighted average period over which unrecognized compensation is expected to be recognized									2 years 3 months 18 days
Stock Options \| Non- Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option issued (in shares)									0	10,000	477,000
Stock option vested (in shares)									119,250	139,187	0
Unvested restricted stock units \| Non- Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted (in shares)									0
2016 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Initial reserves of common stock (in shares)								44,000
Increase in common stock reserved for issuance (in shares)					70,384
Annual percentage of additional shares			5.00%		4.00%
Additional shares authorized (in shares)			4,481,152
Annual limit for non-employee director compensation (in shares)								4,000
Annual limit for non-employee director compensation \| $			$ 750,000
Non-employee director compensation \| $			$ 1,000,000
Additional common stock available for issuance (in shares)												3,814,905	3,023,650		104,561
Shares reserved for issuance (in shares)									10,810,714
Outstanding option awards (in shares)									4,827,082
Dividend yield									0.00%	0.00%	0.00%
2015 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Available for issuance (in shares)								20,395
2018 Equity Inducement Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Initial reserves of common stock (in shares)							44,000
Additional shares authorized (in shares)									750,000	1,000,000
Shares reserved for issuance (in shares)									7,460,440
Outstanding option awards (in shares)									6,620,097
2018 Plan, 2016 Plan and 2015 Plan \| Service Based Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Awards granted, vesting period							4 years
Awards granted, expiration period							10 years
Spyre 2023 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding option awards (in shares)									0					2,734
2016 ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional common stock available for issuance (in shares)												602,570	360,571		26,140
Shares reserved for issuance (in shares)								6,600	972,775
Awards granted, expiration period								10 years
Percentage of fair market value of common stock								85.00%
Percentage of discount through payroll deductions to eligible employees to purchase common stock								15.00%
Maximum purchase value per employee under employee stock purchase plan \| $								$ 25,000
Additional annual percentage increase of common stock						1.00%
Maximum shares purchased under employee stock purchase plan (in shares)		2,000		400				80
Stock-based compensation expense \| $									$ 300,000	$ 300,000	$ 100,000
Dividend yield									0.00%	0.00%	0.00%

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Statement of Comprehensive Income [Abstract]
Net loss	$ (155,203)	$ (208,018)	$ (338,790)
Other comprehensive income (loss):
Foreign currency translation adjustment	(22)	4	37
Unrealized gain (loss) on marketable securities	711	(126)	313
Total comprehensive loss	$ (154,514)	$ (208,140)	$ (338,440)

- Definition

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

+ References + Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Reference 40: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 41: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 42: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 43: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-60B

Reference 44: http://www.xbrl.org/2003/role/disclosureRef
-Topic 205
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483499/205-20-50-7

Reference 45: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 46: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482790/220-10-45-1A

Reference 47: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482790/220-10-45-1B

Reference 48: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 65
-Paragraph 4
-Subparagraph (f)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481538/470-20-65-4

Reference 49: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

+ Details

- Definition

Amount after tax, before reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

+ References + Details

Insider Trading Policies and Procedures	12 Months Ended
Insider Trading Policies and Procedures	Dec. 31, 2025
Insider Trading Policies and Procedures [Line Items]
Insider Trading Policies and Procedures Adopted	true

Asset Acquisition - Schedule of Asset Acquisition Cost (Details) - USD ($) $ in Thousands		12 Months Ended
	Jun. 22, 2023	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Asset Acquisition [Line Items]
Acquired in-process research and development		$ 0	$ 0	$ 130,188
Cash acquired		$ 0	$ 0	$ 3,035
Spyre Therapeutics, Inc.
Asset Acquisition [Line Items]
Consideration transferred in Series A Preferred Stock and common stock	$ 110,000
Transaction costs incurred by the Company	3,200
Acquired in-process research and development	130,200
Cash acquired	3,000
Assumed liabilities	(20,000)
Total cost to acquire asset	$ 113,200

Property and Equipment, Net (Details) - USD ($)	3 Months Ended		12 Months Ended
Property and Equipment, Net (Details) - USD ($)	Jun. 30, 2023	Jun. 30, 2023	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Property Plant And Equipment [Line Items]
Depreciation and amortization			$ 0	$ 0	$ 744,000
Employee workforce, termination percentage		83.00%
Proceeds from the sale of property plant and equipment	$ 500,000		0	0	475,000
Loss on disposal of long-lived assets			0	0	915,000
Research and Development Expense
Property Plant And Equipment [Line Items]
Loss on disposal of long-lived assets	700,000
General and Administrative Expense
Property Plant And Equipment [Line Items]
Loss on disposal of long-lived assets	$ 200,000
Property, Plant and Equipment
Property Plant And Equipment [Line Items]
Depreciation and amortization			$ 0	$ 0	$ 700,000

- Definition

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

+ References + Details

Leases

12 Months Ended

Dec. 31, 2025

Leases [Abstract]

Leases

Prior to the Company's restructuring, as described in Note 17, the Company leased certain office space, laboratory facilities, and equipment. These leases required monthly lease payments that were subject to annual increases throughout the lease term. Certain of these leases also included renewal options at the election of the Company to renew or extend the lease for an additional three to five years. These optional periods were not considered in the determination of the right-of-use assets or lease liabilities associated with these leases as the Company did not consider it reasonably certain it would exercise the options. The Company performed evaluations of its contracts and determined it has both operating and finance leases. Variable lease expense for these leases primarily consisted of common area maintenance and other operating costs.

In April 2019, the Company entered into a lease agreement (the “Las Cimas Lease”) for its corporate headquarters and laboratory space located in Austin, Texas. The Las Cimas Lease included approximately 30,000 square feet and commenced on April 30, 2019, with an expiration on April 30, 2028. The Company posted a customary letter of credit in the amount of $1.5 million as security, which is subject to automatic reductions per the terms of the Las Cimas Lease. A tenant allowance of up to $1.0 million was provided by the lessor and fully reimbursed to the Company.

In August 2023, the Company terminated the Las Cimas Lease. The negotiated termination agreement obligated the Company to pay the lessor a $2.0 million termination fee in exchange for releasing the Company of all further obligations under the lease including terminating the associated letter of credit.

The following table summarizes the lease costs pertaining to the Company’s operating leases (in thousands):


	Year Ended December 31,
	2025		2024		2023
Operating lease cost	$	—	$	—	$	455
Variable lease cost	—		—		471
Total lease cost	$	—	$	—	$	926

Cash paid for amounts included in the measurement of operating lease liabilities during the years ended December 31, 2023 was $0.5 million, respectively, and was included within net cash used in operating activities in the cash flows. There were no such payments for the years ended December 31, 2025 and 2024.

As of December 31, 2025 and 2024, the Company had no operating or finance lease obligations.

Leases

The following table summarizes the lease costs pertaining to the Company’s operating leases (in thousands):


	Year Ended December 31,
	2025		2024		2023
Operating lease cost	$	—	$	—	$	455
Variable lease cost	—		—		471
Total lease cost	$	—	$	—	$	926

As of December 31, 2025 and 2024, the Company had no operating or finance lease obligations.

Cash Equivalents and Marketable Securities - Schedule of Contractual Maturities of Marketable Securities at Estimated Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Cash and Cash Equivalents [Abstract]
Due in one year or less	$ 440,895	$ 338,442
Due in 1 - 2 years	229,917	175,223
Total marketable securities	$ 670,812	$ 513,665

Asset Acquisition (Tables)

12 Months Ended

Dec. 31, 2025

Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract]

Schedule of Asset Acquisition Cost

The Asset Acquisition costs are shown on the following table (in millions):


	June 22, 2023
Consideration transferred in Series A Preferred Stock and common stock	$	110.0
Transaction costs incurred by the Company	3.2
Total cost to acquire asset	$	113.2

The allocation of the purchase price to net assets acquired is as a follows:


	June 22, 2023
Acquired in-process research and development	$	130.2
Cash acquired	3.0
Assumed liabilities	(20.0)
Total cost to acquire asset	$	113.2

Paragon Agreement (Details) $ in Millions		1 Months Ended
Paragon Agreement (Details) $ in Millions	Jun. 22, 2023 USD ($)	May 31, 2023 USD ($) research_program	Mar. 31, 2024	Sep. 29, 2023
Parapyre Option Obligation
Related Party Transaction [Line Items]
Warrants term				10 years
Parapyre Option Obligation
Related Party Transaction [Line Items]
Percentage of annual equity grant of options		1.00%
Related Party
Related Party Transaction [Line Items]
Development cost reduction percentage			50.00%
Paragon Agreement
Related Party Transaction [Line Items]
Number of research programs \| research_program		4
Related party expenses incurred prior to asset acquisition	$ 19.0
Related party expenses unpaid prior to asset acquisition	19.0
Paragon Agreement \| Related Party
Related Party Transaction [Line Items]
Research initiation fees	3.0	$ 3.0
Reimbursable research costs	16.0
Nonrefundable research initiation fee for one program paid in cash	$ 0.8

Leases - Narrative (Details) ft² in Thousands	12 Months Ended
Leases - Narrative (Details) ft² in Thousands	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Aug. 31, 2023 USD ($)	Apr. 30, 2019 USD ($) ft²
Lessee, Lease, Description [Line Items]
Area of land \| ft²					30
Letter of credit					$ 1,500,000
Termination fee amount				$ 2,000,000.0
Operating lease, payments	$ 0	$ 0	$ 500,000
Operating and finance lease obligations	$ 0	$ 0
Minimum
Lessee, Lease, Description [Line Items]
Lessee, operating lease, renewal term	3 years
Maximum
Lessee, Lease, Description [Line Items]
Lessee, operating lease, renewal term	5 years
Tenant improvement allowance (up to)					$ 1,000,000.0

Cash Equivalents and Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2025

Cash and Cash Equivalents [Abstract]

Schedule of Estimated Fair Value of Cash Equivalents and Marketable Securities and the Gross Unrealized Gains and Losses

The following tables summarize the estimated fair value of the Company’s cash equivalents and marketable securities and the gross unrealized gains and losses (in thousands):


	December 31, 2025
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Cash equivalents:
Money market funds	$	74,004	$	—	$	—	$	74,004
Commercial paper	9,987		—		—		9,987

Total cash equivalents	$	83,991	$	—	$	—	$	83,991

Marketable securities:
Commercial paper	$	184,423	$	25	$	(80)	$	184,368
Corporate bonds	100,753		60		(23)		100,790
U.S. government treasury securities	265,316		748		—		266,064
U.S. government agency securities	119,450		153		(13)		119,590
Total marketable securities	$	669,942	$	986	$	(116)	$	670,812


	December 31, 2024
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Cash equivalents:
Money market funds	$	65,902	$	—	$	—	$	65,902
Commercial paper	21,832		6		—		21,838
U.S. government treasury securities	—		—		—		—
Total cash equivalents	$	87,734	$	6	$	—	$	87,740

Marketable securities:
Commercial paper	$	143,265	$	104	$	(77)	$	143,292
Corporate bonds	56,471		25		(48)		56,448
U.S. government treasury securities	227,155		385		(296)		227,244
U.S. government agency securities	86,616		137		(72)		86,681
Total marketable securities	$	513,507	$	651	$	(493)	$	513,665

Schedule of Available-for-Sale Securities in an Unrealized Loss Position


	December 31, 2025
	Less Than 12 Months				12 Months or Longer				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Commercial paper	$	99,837	$	(80)	$	—	$	—	$	99,837	$	(80)
Corporate bonds	58,296		(23)		—		—		58,296		(23)

U.S. government agency securities	22,828		(13)		—		—		22,828		(13)
Total marketable securities	$	180,961	$	(116)	$	—	$	—	$	180,961	$	(116)


	December 31, 2024
	Less Than 12 Months				12 Months or Longer				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Commercial paper	$	67,200	$	(77)	$	—	$	—	$	67,200	$	(77)
Corporate bonds	42,916		(48)		—		—		42,916		(48)
U.S. government treasury securities	126,588		(296)		—		—		126,588		(296)
U.S. government agency securities	12,560		(72)		—		—		12,560		(72)
Total marketable securities	$	249,264	$	(493)	$	—	$	—	$	249,264	$	(493)

Schedule of Contractual Maturities of Marketable Securities at Estimated Fair Value

The following table summarizes the contractual maturities of the Company's marketable securities at estimated fair value (in thousands):


	December 31,
	2025		2024
Due in one year or less	$	440,895	$	338,442
Due in 1 - 2 years	229,917		175,223
Total marketable securities	$	670,812	$	513,665

Strategic License Agreements (Details) - USD ($)		1 Months Ended	12 Months Ended
Strategic License Agreements (Details) - USD ($)	Jul. 27, 2023	Jul. 31, 2021	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Jun. 30, 2023
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue			$ 0	$ 0	$ 886,000
Proceeds from sale of in-process research & development asset			7,000,000	0	15,000,000
Gain on sale of in-process research and development asset			10,000,000	0	16,449,000
Total consideration from disposal of long lived assets						$ 500,000
Contract assets			0	0
Contract liability			0	0
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Global Rights to Pegzilarginase
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Proceeds from sale of in-process research & development asset	$ 15,000,000.0
Contingent consideration	100,000,000.0
Carrying value of assets	0
Gain on sale of in-process research and development asset	16,400,000		10,000,000.0
Contingent reimbursement of pre-paid manufacturing costs	1,800,000
Derecognition of nonfinancial assets and liabilities	$ 400,000
Total consideration from disposal of long lived assets			$ 3,000,000.0	$ 0
Immedica Pharma AB
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Reimbursement		$ 3,000,000.0
Immedica Pharma AB \| PEACE Trial and BLA Package
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue					$ 900,000

Stock-Based Compensation - Schedule of Stock-Based Compensation Expense (Details) - USD ($)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 37,614,000	$ 44,833,000	$ 25,675,000
Related Party
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	1,000,000.0	15,600,000	11,500,000
Employees
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	36,588,000	28,945,000	14,237,000
Stock-based compensation	36,600,000	28,900,000	14,200,000
Non- Employees
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	1,026,000	15,888,000	11,438,000
Legacy Aeglea Employees and Directors
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	0	3,600,000	8,300,000
Research and Development Expense \| Employees
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	16,270,000	9,112,000	2,910,000
Research and Development Expense \| Non- Employees
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	0	14,459,000	11,328,000
General and administrative \| Employees
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	20,318,000	19,833,000	11,327,000
General and administrative \| Non- Employees
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	1,026,000	1,429,000	110,000
Parapyre Option Obligation
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	0
Parapyre Option Obligation \| Related Party
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Stock-based compensation	$ 0	$ 14,500,000	$ 11,400,000

Fair Value Measurements - Schedule of Changes in CVR Liability (Details) - CVR Liability $ in Thousands	12 Months Ended
	Dec. 31, 2025 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 61,700
Changes in the fair value of the CVR liability	(29,769)
Payments	(5,251)
Ending balance	$ 26,680

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2025

Accounting Policies [Abstract]

Schedule of Useful Lives of Property and Equipment

The useful lives of the property and equipment are as follows:


Laboratory equipment			5 years
Furniture and office equipment			5 years
Computer equipment			3 years
Software			3 years
Leasehold improvements			Shorter of remaining lease term or estimated useful life

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2025

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Net Loss Per Share


	Year Ended December 31, 2025
	Series A Preferred Stock		Series B Preferred Stock		Common Stock
Net loss per share, basic and diluted:
Numerator
Allocation of losses	$	(27,344)	$	(1,317)	$	(126,541)
Denominator
Weighted-average shares outstanding	346,045		16,667		64,056,442


Net loss per share, basic and diluted	$	(79.02)	$	(79.02)	$	(1.98)

	Year Ended December 31, 2024
	Series A Preferred Stock		Series B Preferred Stock		Common Stock
Net loss per share, basic and diluted:
Numerator
Allocation of losses	$	(47,624)	$	(10,839)	$	(149,555)
Denominator
Weighted-average shares outstanding	374,387		85,208		46,940,206
Weighted-average pre-funded warrants outstanding	—		—		87,432
Number of shares used in per share computation	374,387		85,208		47,027,638
Net loss per share, basic and diluted	$	(127.21)	$	(127.21)	$	(3.18)

	Year Ended December 31, 2023
	Series A Preferred Stock		Series B Preferred Stock		Common Stock
Net loss per share, basic and diluted:
Numerator
Allocation of losses	$	(239,158)	$	(4,749)	$	(94,883)
Denominator
Weighted-average shares outstanding	434,612		8,630		6,201,954
Weighted-average pre-funded warrants outstanding	—		—		695,111
Number of shares used in per share computation	434,612		8,630		6,897,065
Net loss per share, basic and diluted	$	(550.28)	$	(550.29)	$	(13.76)

Schedule of Weighted-Average Equity Instruments Excluded from Calculation of Diluted Net Loss Per Share

The following weighted-average equity instruments were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive for the periods presented:


	Year Ended December 31,
	2025	2024	2023
Options to purchase common stock	1,785,568	3,212,734	2,583,226
Unvested restricted stock units	27,806	68,027	4,240
Outstanding Parapyre Warrants	1,532,591	686,724	5,625.00