Voyager Therapeutics, Inc.

Voyager Therapeutics, Inc. (the “Company”) is a biotechnology company whose mission is to leverage the power of human genetics to modify the course of and ultimately cure neurological diseases. Its pipeline includes programs for Alzheimer’s disease (“AD”); Friedreich’s ataxia (“FA”); Parkinson’s disease (“PD”); and multiple other diseases of the central nervous system (“CNS”). Its pipeline includes programs it wholly owns and programs which it is advancing with licensees and collaborators including Alexion, AstraZeneca Rare Disease, or Alexion; Novartis Pharma AG, or Novartis; and Neurocrine Biosciences, Inc., or Neurocrine.

Many of its programs are derived from the Company’s TRACER™ (Tropism Redirection of AAV by Cell-type-specific Expression of RNA) adeno-associated virus (“AAV”) capsid discovery platform, which it has used to generate novel capsids (“TRACER Capsids”) and identify associated receptors to potentially enable high brain penetration with genetic medicines following intravenous (“IV”) dosing. TRACER is a broadly applicable, RNA-based screening platform that enables rapid discovery of AAV capsids with robust penetration of the blood-brain barrier (“BBB”) and enhanced CNS tropism in multiple species, including non-human primates. The Company is also developing a second non-viral therapeutics platform focused on non-viral receptor-mediated transport across the BBB, the Voyager NeuroShuttle TM platform.

Despite reporting net income for the year ended December 31, 2023, the Company has a history of incurring significant losses. As of December 31, 2025, the Company had an accumulated deficit of $445.9 million. The Company has not generated any product revenue and has financed its operations primarily through public offerings and private placements of its equity securities and funding from fees, milestone payments, and cost reimbursements associated with its prior and current collaborations and license agreements.

As of December 31, 2025, the Company had cash, cash equivalents, and marketable securities of $201.7 million. Based upon its current operating plan, the Company expects that its existing cash, cash equivalents, and marketable securities at December 31, 2025 to be sufficient to meet the Company’s planned operating expenses and capital expenditure requirementsfor at least twelve months from the issuance of these consolidated financial statements.

There can be no assurance that the Company will be able to obtain additional debt or equity financing on terms acceptable to the Company or generate product revenue or revenue from collaboration partners, on a timely basis or at all. The failure of the Company to obtain sufficient funds on acceptable terms when needed could have a material adverse effect on the Company’s business, results of operations, and financial condition.

Basis of presentation

The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) for reporting on Form 10-K. The Company’s consolidated financial statements include the accounts of Voyager Therapeutics, Inc. and its wholly-owned subsidiary, Voyager Securities Corporation. All intercompany balances and transactions have been eliminated.

Use of Estimates

The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates, which include, but are not limited to, estimates related to revenue recognition, research and development accrued expenses, stock-based compensation expense, and income taxes. The Company bases its estimates on historical experience and other market specific or other

relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions.

Fair Value of Financial Instruments

Accounting Standards Codification (“ASC”) Topic 820,Fair Value Measurement (“ASC 820”), establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability, and are developed based on the best information available in the circumstances.

ASC 820 identifies fair value as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tier fair value hierarchy that distinguishes between the following:

To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.

The carrying amounts reflected in the balance sheets for cash and cash equivalents, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values, due to their short-term nature.

Cash and Cash Equivalents

The Company considers all highly liquid investments purchased with original maturities of 90 days or less at acquisition to be cash equivalents. Cash and cash equivalents include cash held in banks and amounts held in money market funds.

Marketable Securities

The Company classifies marketable securities with a remaining maturity of greater than three months when purchased as available-for-sale. Marketable securities with a remaining maturity date greater than one year are classified as non-current where the Company has the intent and ability to hold these securities for at least the next 12 months.

All available-for-sale debt securities are carried at fair value with the unrealized gains and losses included in other comprehensive (loss) income as a component of stockholders’ equity until realized. Any premium or discount arising at purchase is amortized and/or accreted to interest income and/or expense. Realized gains and losses are determined using the specific identification method and are included in other income.

If any adjustment to fair value reflects a decline in value of the investment, the Company uses a forward-looking approach based on expected losses to estimate credit losses on certain types of financial instruments, including available-for-sale debt securities. No credit losses have been recognized.

The Company reviews investments whenever the fair value of an investment is less than the amortized cost and evidence indicates that an investment’s carrying amount is not recoverable within a reasonable period of time. In connection with these investments, the Company evaluates whether the decline in fair value has resulted from credit losses or other factors, considering 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, the present value of cash flows expected to be collected from the security is compared to the amortized cost basis of the security. If the present value of cash flows expected to be collected is less than the amortized cost basis, a credit loss exists and an allowance for credit losses is recorded for the credit loss on the consolidated balance sheet, limited by the amount that the fair value is less than the amortized cost basis. Any impairment that is not related to credit is recognized in other comprehensive (loss) income. Changes in the allowance for credit losses are recorded as a provision for (or reversal of) credit loss expense in general and administrative expenses within the consolidated statement of operations and comprehensive (loss) income. Losses are charged against the allowance when the Company believes the uncollectability of an available-for-sale security is confirmed or when either of the criteria regarding intent or requirement to sell is met.

Cash equivalents and marketable securities as of December 31, 2025 and 2024 consist of the following:

All of the Company’s marketable securities at December 31, 2025 and 2024 have a contractual maturity oftwo years or less.

As of December 31, 2025, the Company held 20 marketable securities that were in an unrealized loss position, representing $26.6 million in fair value. As of December 31, 2024, the Company held 97 marketable securities that were in an unrealized loss position, representing $156.3 million in fair value. The unrealized losses at December 31, 2025, and December 31, 2024, were attributable to changes in interest rates and the unrealized losses do not represent credit losses. The Company does not intend to sell these securities, and it is not likely that it will be required to sell them before recovery of their amortized cost basis.

Restricted Cash

As of December 31, 2025 and 2024, the Company maintained restricted cash totaling approximately $2.7 million and $2.9 million, respectively, held in the form of money market accounts as collateral for the Company’s facility lease obligations. The following table provides a reconciliation of cash, cash equivalents, and restricted cash within the consolidated balance sheets that sum to the total of the same such amounts shown in the statements of cash flows:

Property and Equipment, net

Property and equipment consists of laboratory equipment, furniture and office equipment, and leasehold improvements and is stated at cost, less accumulated depreciation. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed to operations as incurred; while costs of major additions and betterments are capitalized. Depreciation is calculated over the estimated useful lives of the assets using the straight-line method.

Impairment of Long-Lived Assets

The Company evaluates long-lived assets for potential impairment when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparing the book values of the assets to the expected future net undiscounted cash flows that the assets are expected to generate. If such assets are impaired, the impairment to be recognized is measured by the amount by which the book values of the assets exceed their fair value. During the year ended December 31, 2024, the Company recorded an impairment loss of $2.8 million as a result of the carrying value of the leased office and laboratory space asset group in Cambridge, Massachusetts exceeding the undiscounted cash flows projected from a planned sublease of the facility. The Company did not record any impairment losses on long-lived assets during the years ended December 31, 2025 and 2023.

Revenue Recognition

The Company enters into license, option, and collaboration agreements which are within the scope of ASC Topic 606,Revenue from Contracts with Customers (“ASC 606”), under which the Company licenses or provides options to license certain of the Company’s product candidates and, in certain cases, performs research and development services. The terms of these arrangements typically include payment of one or more of the following: non-refundable, upfront fees; reimbursement of research and development costs; option exercise fees; development, regulatory, and commercial milestone payments; and royalties on net sales of licensed products.

The promised goods or services in the Company’s arrangements typically consist of license rights to the Company’s intellectual property and research and development services. The Company provides options to additional items in the contracts, which are accounted for as separate contracts when the customer elects to exercise such options, unless the option provides a material right to the customer. The Company evaluates the customer options for material rights, or options to acquire additional goods or services for free or at a discount. If the customer options are determined to represent a material right, the material right is recognized as a separate performance obligation at the outset of the arrangement. Performance obligations are promised goods or services in a contract to transfer a distinct good or service to the customer and are considered distinct when (a) the customer can benefit from the good or service on its own or together with other readily available resources and (b) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised goods or services are distinct, the Company considers factors such as the stage of development of the underlying intellectual property, the capabilities of the customer to develop the

intellectual property on its own or whether the required expertise is readily available and whether the goods or services are integral or dependent to other goods or services in the contract.

The Company estimates the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration or variable consideration. At the inception of each arrangement that includes variable consideration, the Company evaluates the amount of potential payments and the likelihood that the payments will be received. The Company utilizes either the most likely amount method or expected value method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration that is included in the transaction price may be constrained and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period.

The Company’s contracts often include development and regulatory milestone payments that are assessed under the most likely amount method and constrained if it is probable that a significant revenue reversal would occur. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of such development and regulatory milestones 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, which would affect collaboration revenue in the period of adjustment.

For arrangements that include sales-based royalties, including milestone payments based on the level of sales, in which the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (a) when the related sales occur, or (b) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any consideration related to sales-based royalty revenue resulting from any of the Company’s collaboration or license arrangements.

The Company allocates the transaction price based on the estimated stand-alone selling price of each of the performance obligations. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price for service obligations, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs to satisfy the performance obligation. Additionally, in determining the standalone selling price for material rights, the Company utilizes comparable transactions, clinical trial success probabilities, and estimates of option exercise likelihood. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts the Company would expect to receive for the satisfaction of each performance obligation.

The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations which consist of licenses and other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition.

Upfront payments and fees are recorded as contract liabilities within deferred revenue on the consolidated balance sheets until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. A portion of revenue recognized from the 2019 Neurocrine Collaboration Agreement and the 2023 Neurocrine Collaboration Agreement relate to performance obligations pursuant to which revenue is recognized using a proportional performance model. Revenue is recognized using input-based measurements, which involves the measurement of progress toward each performance obligation based on the actual costs incurred compared to total expected costs. The Company estimates the expected remaining costs to complete the research and development services for each performance obligation. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure and related revenue recognition. In

general, the uncertainty associated with expected costs to complete the research and development services decreases as the remaining services near the end of their contractual term.

Research and Development

Research and development costs are charged to expense as incurred. The costs include employee compensation costs, external research, consultant costs, sponsored research, license fees, process development and facilities costs. Facilities costs primarily include the allocation of rent, utilities and depreciation.

Leases

The Company determines if an arrangement is or contains a lease at inception under ASC Topic 842Leases. For leases with a term of 12 months or less, the Company does not recognize a right-of-use asset or lease liability. The Company's operating leases are recognized on its consolidated balance sheets as operating lease right-of-use asset and operating lease liabilities. The Company does not have any finance leases.

Right-of-use 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. Operating lease right-of-use assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. As the Company’s leases typically do not provide an implicit rate, the Company uses an estimate of its incremental borrowing rate based on the information available at the lease commencement date in determining the present value of lease payments. Operating lease right-of-use assets also include the effect of any lease prepayments or deferred lease payments and are reduced by lease incentives. The lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense is recognized on a straight-line basis over the lease term.

The Company has lease agreements with lease and non-lease components, which are generally accounted for separately. Non-lease components as it pertains to the Company's leased premises generally refer to common area maintenance charges related to the premises.

Research Contract Costs and Accruals

The Company has entered into various research and development contracts with research institutions and other companies. These agreements are generally cancelable. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Judgments and estimates may be required in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.

Patent Costs

The Company expenses patent application and related legal costs as incurred and classifies such costs as general and administrative expenses in the accompanying statements of operations.

Stock-Based Compensation Expense

The Company accounts for its stock-based compensation awards in accordance with ASC Topic 718Compensation—Stock Compensation (“ASC 718”). ASC 718 requires all stock-based payments to employees, directors, and other service providers, referred to as non-employees, including grants of restricted stock units and stock options, to be recognized as expense in the consolidated statements of operations and comprehensive (loss) income based on their grant date fair values. The Company estimates the fair value of options granted using the Black-Scholes option pricing model. The Company uses the fair value of its common stock to determine the fair value of restricted stock awards and restricted stock units.

The Black-Scholes option pricing model requires inputs based on certain assumptions, including (a) the expected stock price volatility, (b) the expected term of the award, (c) the risk-free interest rate and (d) expected dividends. The Company bases the estimate of expected volatility on the historical volatility of its common stock. The historical volatility is calculated based on the Company’s historical volatility over a period of time commensurate with the expected term assumption. The Company uses the simplified method as prescribed by the SEC Staff Accounting Bulletin No. 107,Share-Based Payment, to calculate the expected term for stock options granted to employees as it does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term. For stock options granted to non-employees, the Company utilizes the contractual term of the arrangement as the basis for the expected term assumption. The risk-free interest rate is based on a treasury instrument whose term is consistent with the expected term of the stock options. The expected dividend yield is assumed to bezero as the Company has never paid dividends and has no current plans to pay any dividends on its common stock.

The Company expenses the fair value of its stock-based compensation awards on a straight-line basis over the derived service period, which is generally the period in which the related services are received, adjusted for actual forfeitures of unvested awards as they occur.

The Company records the expense for stock-based compensation awards subject to performance conditions over the remaining service period when management determines that achievement of the performance condition is probable. Management evaluates when the achievement of a performance condition is probable based on the expected satisfaction of the performance conditions as of the reporting date.

Income Taxes

Income taxes are recorded in accordance with ASC Topic 740,Income Taxes (“ASC 740”), which provides for deferred taxes using an asset and liability approach. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial reporting and the tax reporting basis of assets and liabilities and are measured using the enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. The Company provides a valuation allowance against net deferred tax assets unless, based upon the weight of available evidence, it is more likely than not that the deferred tax assets will be realized.

The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. As of December 31, 2025, the Company does not have any significant uncertain tax positions.

Comprehensive (Loss) Income

Comprehensive (loss) income is comprised of net (loss) income and other comprehensive income or loss. Other comprehensive income or loss consists of unrealized gains or losses on marketable securities.

Net (Loss) Income Per Share

Basic net (loss) income per share is calculated by dividing the net (loss) income by the weighted-average number of shares of common stock outstanding during the period, without consideration for potentially dilutive securities. Pre-funded warrants are included within the weighted-average number of shares of common stock outstanding during the period given their nominal exercise price. Diluted net (loss) income per share is computed by dividing the net (loss) income by the weighted-average number of shares of common stock and potentially dilutive securities outstanding for the period determined using the treasury-stock and if-converted methods.

For purposes of the diluted net (loss) income per share calculation, unvested restricted common stock and outstanding stock options are considered to be potentially dilutive securities. Unvested restricted common stock and outstanding stock options were excluded from the calculation of diluted net loss per share in the years ended December 31, 2025 and 2024, because their effect would be anti-dilutive and therefore, basic and diluted net loss per

share were the same for the years ended December 31, 2025 and 2024. Certain unvested restricted common stock and outstanding options were also excluded from the calculation of diluted net income per share in the year ended December 31, 2023, because their effect would be anti-dilutive.

The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net (loss) income per share because to do so would be anti-dilutive:

Basic net (loss) income and diluted weighted-average shares outstanding are as follows for the years ended December 31, 2025, 2024, and 2023:

Concentrations of Credit Risk and Significant Suppliers

The Company hasno financial instruments with off-balance sheet risk such as foreign exchange contracts, option contracts or other foreign currency hedging arrangements. Financial instruments that potentially subject the Company to a concentration of credit risk are cash and cash equivalents, marketable securities and accounts receivable. The Company’s cash, cash equivalents and marketable securities are held in accounts at financial institutions that may exceed federally insured limits. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds.

During the years ended December 31, 2025, 2024 and 2023, the Company generated all of its revenue from its collaborative research and license agreements. As of December 31, 2025 and 2024, accounts receivable consisted of amounts due from the Company’s principal collaborators. For more information, refer to Note 9, Significant Agreements.

The Company is dependent on third-party manufacturers to supply certain products for research and development activities in its programs. In particular, the Company relies on a sole manufacturer to supply it with specific vectors related to the Company’s research and development programs.

Recently Adopted Accounting Pronouncement

In December 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2023-09, “*Income Taxes (Topic 740) - Improvements to Income Tax Disclosures.”*ASU 2023-09 enhances the transparency and decision usefulness of income tax disclosures by requiring consistent categories and greater disaggregation of information in the rate reconciliation and income taxes paid disaggregated by jurisdiction. The amendments in ASU 2023-09 are effective for fiscal years, and interim periods within those fiscal years, beginning after

December 15, 2024, and is applicable to the Company in fiscal year 2025. The Company retrospectively adopted ASU 2023-09 within its consolidated financial statements for all periods presented and has included the applicable disclosures within Note 14, Income Taxes.

In September 2025, the FASB issued ASU 2025-07, “Derivatives and Hedging (Topic 815) and Revenue from Contracts with Customers (Topic 606): Derivatives Scope Refinements and Scope Clarification for Share-Based Noncash Consideration from a Customer in a Revenue Contract.” ASU 2025-07 excludes from the scope of Topic 815,Derivatives and Hedging, certain contracts that are not traded on an exchange that include underlyings based on the operations or activities of one of the parties to the contract. The guidance also clarifies that an entity receiving share-based noncash consideration from a customer for the transfer of goods or services in a revenue contract is required to apply the noncash consideration guidance in Topic 606,Revenue from Contracts with Customers, unless and until the entity’s right to receive or retain the share-based noncash consideration is unconditional under Topic 606. Effective January 1, 2025, the Company early adopted ASU 2025-07 on a prospective basis. The adoption of this guidance did not have a material impact on the Company’s consolidated financial statements and related disclosures.

Recently Issued Accounting Pronouncement not yet Adopted

In November 2024, the FASB issued ASU No. 2024-03, “*Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Subtopic 220-40).”*The amendments in ASU 2024-03 require disclosure, in the notes to financial statements, of specified information about certain costs and expenses. ASU 2024-03 is effective for annual reporting periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027, for all public entities. Early adoption is permitted. Management is currently evaluating the impact of this update on the Company’s financial statements.

3. Fair value measurements

Assets and liabilities measured at fair value on a recurring basis as of December 31, 2025, and 2024 are as follows:

The Company measures the fair value of money market funds, U.S. Treasury notes and U.S. Government agency securities based on quoted prices in active markets for identical securities. The Company measures the fair value of the Level 2 securities, corporate bonds, certificates of deposit, and commercial paper, based on recent trades of securities in inactive markets or based on quoted market prices of similar instruments and other significant inputs derived from or corroborated by observable market data.

4. Prepaid expenses and other current assets

Prepaid expenses and other current assets consist of the following:

5. Property and equipment, net

Property and equipment, net consists of the following:

The Company recorded $4.1 million, $4.7 million, and $4.4 million in depreciation expense during the years ended December 31, 2025, 2024, and 2023, respectively.

6. Accrued expenses

Accrued expenses consist of the following:

During the year ended December 31, 2025, the Company recognized $4.3 million in severance costs related to restructurings in June 2025 and December 2025. Of this amount, $1.9 million is accrued as of December 31, 2025 and included within “employee compensation costs” above.

7. Lease obligation

Operating Leases

As of December 31, 2025, the Company has a lease for laboratory and office space at 75 Hayden Avenue in Lexington, Massachusetts through January 31, 2031, and a lease for additional office and laboratory space at 64 Sidney Street in Cambridge, Massachusetts (the “Cambridge Facility”) through November 30, 2026.

In August 2023, the Company entered into a first amendment (the “First Amendment”) to its existing lease for laboratory and office space at 75 Hayden Avenue in Lexington, Massachusetts, pursuant to which the Company agreed to lease approximately 61,307 square feet of additional office and laboratory space. The commencement date for the First Amendment occurred on February 1, 2024. The expected contractual obligation under the First Amendment to the Company’s existing lease is approximately $35.4 million, to be paid over the 7-year term of the lease.

The Company’s lease agreements require the Company to maintain a cash deposit or irrevocable letter of credit in the aggregate amount of $2.7 million payable to its landlords as security for the performance of its obligations under the leases. These amounts are recorded as restricted cash in the accompanying consolidated balance sheets.

In June 2024, the Company vacated its leased office and laboratory space in Cambridge, Massachusetts. The Company recorded an impairment charge of $2.8 million to operating expenses during the second quarter of 2024 as a result of the carrying value of the leased office and laboratory space asset group exceeding the undiscounted cash flows projected from a planned sublease of the facility. The impairment charge reduced the carrying value of the leased office and laboratory space asset group by $2.8 million. In August 2024, the Company executed the sublease of the Cambridge Facility (the “Sublease Agreement”). Payments received under the Sublease Agreement are included in other income in the consolidated statements of operations and comprehensive (loss) income.

Total lease cost for operating leases of approximately $7.5 million, $10.0 million, and $3.6 million was incurred during the years ended December 31, 2025, 2024, and 2023, respectively. This includes $2.8 million in impairment charges recognized during the year ended December 31, 2024. As of December 31, 2025, the weighted average remaining lease term was 3.7 years, and the weighted average incremental borrowing rate used to determine the operating lease liability was 6.5%. As of December 31, 2024, the weighted average remaining lease term was 4.7 years, and the weighted average incremental borrowing rate used to determine the operating lease liability was 6.8%.

The following table summarizes the operating sublease income generated under the Sublease Agreement for the years ended December 31, 2025, 2024, and 2023:

Future minimum lease payments due under operating leases are as follows:

8. Commitments, contingencies, and other liabilities

Other Agreements

In 2016, the Company entered into a research and development funding arrangement with a non-profit organization that provided up to $4.0 million in funding to the Company upon the achievement of clinical and development milestones. The agreement as amended in 2022 provides that the Company is obligated to repay amounts received under certain circumstances, including termination of the agreement, and to pay an amount up to 2.6 times the funding received upon successful development and commercialization of any products developed. In 2017, the Company earned a milestone payment of $1.0 million. The Company evaluated the arrangement and concluded that it represents a research and development financing arrangement as it is probable that the Company will repay amounts received under the arrangement. As a result, the $1.0 million is recorded as a non-current liability in the consolidated balance sheet.

In November 2022, the Company and Touchlight IP Limited (“Touchlight”) entered into a license agreement (the “Touchlight License Agreement”) to authorize historical use by the Company of a certain DNA preparation process ( the “Subject DNA Preparation Process”), and to authorize the prospective exploitation of TRACER Capsids created with the use of the Subject DNA Preparation Process. The terms of the Touchlight License Agreement include future milestone payments and low single-digit royalties payable to Touchlight by the Company if the Company or its program collaborators or licensees choose to utilize in a therapeutic product certain TRACER Capsids that were created with the historical use of the Subject DNA Preparation Process. Additionally, the Company is obligated to pay low single-digit royalties to Touchlight on future payments it receives in connection with licensing of certain TRACER Capsids that were created with the historical use of the Subject DNA Preparation Process, excluding the licensing of or collaboration on any of the Company’s therapeutic programs.

In June 2025, the Company and Transition Bio, Inc. (“Transition Bio”) entered into a license agreement (the “Transition Bio License Agreement”) under which Transition Bio is responsible for the discovery and optimization of small molecules targeting TDP-43 until nomination of a development candidate, upon which the Company will have an option to license the worldwide exclusive rights to develop and commercialize the program. The Transition Bio License Agreement contains a termination for convenience clause, which allows for either party to terminate the arrangement for any reason or no reason upon sixty days’ prior written notice. The Transition Bio License Agreement superseded a prior agreement between the Company and Transition Bio dated December 24, 2024. In the event that the Company terminates the Transition Bio License Agreement due to a change in control, the Company is obligated to pay Transition Bio up to $2.0 million in termination fees.

In connection with a prior agreement between the parties, the Company paid Transition Bio a low single-digit million dollar upfront payment, which was expensed as research and development expense in the year ended December 31, 2024. Additionally, during the fourth quarter of 2025, the Company paid Transition Bio a low single-digit million dollar payment for the achievement of a research milestone, which was also expensed as research and development expense during the year ended December 31, 2025. The terms of the Transition Bio License Agreement include future payments based on potential research, development, commercial and net sales milestones. Additionally, the Company is obligated to pay high single-digit to low double-digit royalties to Transition Bio on net sales during the royalty term of up toten years.

Litigation

The Company was not a party to any material legal matters or claims and didnot have contingency reserves established for any litigation liabilities as of December 31, 2025, or 2024.

9. Significant Agreements

2023 Novartis Collaboration Agreement

In December 2023, the Company entered into a License and Collaboration Agreement (the “2023 Novartis Collaboration Agreement”) with Novartis to (a) provide rights to Novartis with respect to certain TRACER Capsids for use in the research, development, and commercialization by Novartis of AAV gene therapy products and product candidates, comprising such TRACER Capsids and payloads intended for the treatment of spinal muscular atrophy (the “Novartis SMA Program”) and (b) collaborate to develop AAV gene therapy products and product candidates intended for the treatment of Huntington’s disease (the “Novartis HD Program”), in each case, leveraging TRACER Capsids and other intellectual property controlled by the Company.

Novartis SMA Program and Novartis HD Program Licenses

Under the terms of the 2023 Novartis Collaboration Agreement, the Company granted Novartis and its affiliates:

The Company and Novartis have agreed to manage the Novartis HD Program through a Joint Steering Committee until dissolved after the first IND application filing for a Novartis HD Program Product. The Company and

Novartis have further agreed that day-to-day activities of both the Novartis SMA Program and the Novartis HD Program shall be managed through designees from each of the Company and Novartis, acting as alliance managers.

Development, Regulatory Approval, Commercialization and Diligence

Under the 2023 Novartis Collaboration Agreement, Novartis is solely responsible for, and has sole decision-making authority with respect to, at its own expense, the exploitation of a Novartis SMA Program Product.

With respect to the Novartis HD Program, the parties have agreed to conduct research and pre-clinical development of Novartis HD Program Products pursuant to a research plan, with Novartis reimbursing the Company for its activities thereunder in accordance with the agreed-to budget. From and after the first IND application filing for the Novartis HD Program, the parties have agreed that Novartis will assume sole responsibility for the development and commercialization of Novartis HD Program Products, including all further preclinical and clinical development and any commercialization of the Novartis HD Program products and product candidates.

With respect to each of the Novartis SMA Program Products and Novartis HD Program Products, Novartis is obligated to use commercially reasonable efforts to develop and obtain regulatory approval for at leastone of each such product in the United States and in certain other international markets specified in the 2023 Novartis Collaboration Agreement.

Unless earlier terminated, with respect to any licensed product(s) under the 2023 Novartis Collaboration Agreement, on a country-by-country basis, the 2023 Novartis Collaboration Agreement expires upon the expiration of the last-to-expire royalty term with respect to such licensed product in such country in the territory (the “2023 Novartis Collaboration Term”). Novartis may terminate the 2023 Novartis Collaboration Agreement, in whole or in part, for any or no reason upon ninety days’ written notice to the Company. The 2023 Novartis Collaboration Agreement may also be terminated by either party under specific circumstances, including the other party’s uncured material breach.

Under the 2023 Novartis Collaboration Agreement, Novartis paid the Company an upfront payment of $80.0 million. The Company is eligible to receive specified development, regulatory, and commercialization milestone payments of up to an aggregate of $200.0 million for the Novartis SMA Program and up to an aggregate of $225.0 million for the Novartis HD Program, in each case for the first corresponding product to achieve the corresponding milestone. The Company is also eligible to receive (a) specified sales milestone payments of up to an aggregate of $400.0 million for the Novartis SMA Program and up to an aggregate of $375.0 million for the Novartis HD Program and (b) tiered, escalating royalties in the high single-digit to low double-digit percentages of annual net sales of the Novartis SMA Program Products and the Novartis HD Program Products. The royalties are subject to potential customary reductions, including patent claim expiration, payments for certain third-party licenses, and biosimilar market penetration, subject to specified limits.

Stock Purchase Agreement

Under the stock purchase agreement with Novartis entered into on December 28, 2023 (the “2023 Novartis Stock Purchase Agreement”), Novartis purchased 2,145,002 shares of common stock of the Company (the “Novartis Shares”) for an aggregate purchase price of approximately $20.0 million.

The Company determined the 2023 Novartis Collaboration Agreement represents a contract with a customer under ASC 606. As discussed below, the 2023 Novartis Collaboration Agreement did not modify the scope or price of the 2022 Novartis Option and License Agreement. Accordingly, the Company determined that the 2023 Novartis Collaboration Agreement should be accounted for separately. The 2023 Novartis Collaboration Agreement includes the

following performance obligations: (i) the development and commercialization license for the Novartis SMA Program, (ii) the development and commercialization license for the Novartis HD Program; and (iii) the research and development services for the Novartis HD Program (“Novartis HD Research Services”). The development and commercialization licenses for the Novartis HD Program and Novartis SMA Program are each distinct, as Novartis can benefit from such licenses on their own or from other resources commonly available in the industry given the stage of development of the product candidates subject to the licenses. Similarly, the research and development services for the Novartis HD Program provide a distinct benefit to Novartis within the context of the contract, separate from the licenses.

The transaction consideration allocated to the performance obligations within the 2023 Novartis Collaboration Agreement includes fixed consideration of $80.0 million, and variable consideration, which is comprised of an estimated $24.2 million of cost reimbursements for Novartis HD Research Services, up to $425.0 million of potential development milestone payments, up to $775.0 million of potential sales milestone payment, and sales-based royalties. The consideration related to the Novartis HD Research Services, becomes due and payable on a quarterly basis as the services are being performed.

The Company estimates variable consideration using the most likely amount approach. At the outset of the contract, the Company has determined this consideration should be constrained. The sales milestone payments and royalties will be recognized in the period the underlying sales occur, as this consideration is related to thetwo development and commercialization licenses, the predominant performance obligations in the contract.

The Company allocated the fixed transaction price to the separate performance obligations based on the relative standalone selling price of each performance obligation. The standalone selling prices for development and commercialization licenses for the Novartis SMA Program and Novartis HD Program were estimated using an adjusted-market approach. The Company allocated the variable consideration related to the Novartis HD Research Services as the consideration becomes payable as the Company delivers the Novartis HD Research Services and allocating the entirety of this consideration to the Novartis HD Research Services reflects the amount the Company expects to be entitled to for performing the services. The development milestone payments, the sales milestone payments and the royalties are allocated to the respective development and commercialization licenses for the Novartis SMA Program and Novartis HD Program as the variable consideration relates directly to those performance obligations.

The Company recognized the $80.0 million fixed transaction price allocated to the development and commercialization licenses for the Novartis SMA Program and Novartis HD Program, as collaboration revenue upon delivery of the development and commercialization licenses to Novartis in December 2023 and such amount was collected in January 2024. The issuance of the Novartis Shares to Novartis pursuant to the 2023 Novartis Stock Purchase Agreement in January 2024 resulted in a premium of $0.7 million. The premium was allocated to the development and commercialization licenses for the Novartis HD Program and Novartis SMA Program and was recognized as collaboration revenue during the first quarter of 2024, upon the issuance of the Novartis Shares under the 2023 Novartis Stock Purchase Agreement. The Novartis HD Research Services commenced in the first quarter of 2024.

During the year ended December 31, 2025, the Company recognized $5.9 million of collaboration revenue associated with research and development services performed during the period and the corresponding cost reimbursement receivable for the Novartis HD Program. Additionally, as of December 31, 2025, there was $1.8 million of accounts receivable related to reimbursable costs expected to be received from Novartis for research and development services performed.

During the year ended December 31, 2024, the Company recognized $4.2 million of collaboration revenue associated with research and development services performed during the period and the corresponding cost reimbursement receivable for the Novartis HD Program. Additionally, as of December 31, 2024, there was $1.5 million of accounts receivable related to reimbursable costs expected to be received from Novartis for research and development services performed.

During the year ended December 31, 2023, the Company recognized $80.0 million of collaboration revenue related to the development and commercialization licenses for the Novartis SMA Program and Novartis HD Program.

The Company incurred approximately $1.9 million of business development costs related to the 2023 Novartis Collaboration Agreement, which were payable only upon the execution of the agreement and therefore are considered incremental costs of obtaining a contract with a customer. Given the substantial value associated with the development and commercialization licenses for the Novartis SMA Program and Novartis HD Program that were delivered in December 2023, the Company recognized the $1.9 million of costs in general and administrative expenses during the year ended December 31, 2023.

2022 Novartis Option and License Agreement

On March 4, 2022, the Company entered into an option and license agreement with Novartis (the “2022 Novartis Agreement”). Pursuant to the 2022 Novartis Agreement, the Company granted Novartis options (the “Novartis License Options”) to license TRACER Capsids (the “Novartis Licensed Capsids”) for exclusive use in programs targeting three specified genes (the “Initial Novartis Targets”), to develop and commercialize AAV gene therapy candidates comprised of Novartis Licensed Capsids and payloads directed to such targets (the “Novartis Initial Licensed Products”). Effective as of March 1, 2023, Novartis exercised its Novartis License Options to license TRACER Capsids for use in gene therapy programs againsttwo undisclosed programs targeting specified genes. Upon Novartis’ exercise of the two Novartis License Options for Initial Novartis Targets, the Company granted Novartis a target-exclusive, worldwide license, with the right to sublicense, under certain of the Company’s intellectual property, the rights to develop and commercialize the applicable Novartis Licensed Capsid as incorporated into Novartis Initial Licensed Products. The Company also agreed to provide certain additional know-how to enable Novartis to exploit the Novartis Licensed Capsid and a payload directed to the applicable Initial Novartis Target for use in a Novartis Initial Licensed Product. Novartis elected not to license a capsid forone Initial Novartis Target prior to the expiration of the applicable Novartis License Option. As a result, the non-exclusive research license that the Company granted to Novartis in connection with this third Initial Novartis Target terminated, and all capsid rights with respect to that Initial Novartis Target returned to the Company.

On September 3, 2024, the Company entered into an amendment (the “Novartis Amendment”) to the 2022 Novartis Agreement. Pursuant to the Novartis Amendment, the Company agreed to amend the 2022 Novartis Agreement to incorporate the grant to Novartis of a direct license (the “Novartis Direct License”) to a TRACER Capsid (the “Novartis Direct Licensed Capsid”) for exclusive use with a certain gene (the “Novartis Direct License Target”) to develop and commercialize the Novartis Direct Licensed Capsid as incorporated into AAV gene therapy candidates comprised of the Novartis Direct Licensed Capsid and a payload directed to the Novartis Direct License Target (“Novartis Direct Licensed Products”). Thetwo Initial Novartis Targets for which Novartis has exercised its Novartis License Options and the Novartis Direct License Target collectively are the “Novartis Licensed Targets,” and the Novartis Initial Licensed Products and Novartis Direct Licensed Products collectively are “Novartis Licensed Products”.

In October 2025, Novartis notified the Company of its partial termination of the 2022 Novartis Agreement with respect to (a)one Initial Target and (b) the Direct License Target, in each case effective February 1, 2026 (the “Effective Partial Termination Date”) and as such terms are defined in the 2022 Novartis Agreement. The 2022 Novartis Agreement remains in full force and effect for the remaining program thereunder. Upon the Effective Partial Termination Date, the licenses the Company has granted to Novartis with respect to the undisclosed Initial Target and the undisclosed Direct License Target expired, and all intellectual property rights that the Company licensed to Novartis with respect to such programs reverted to the Company in accordance with the 2022 Novartis Agreement. As of the Effective Partial Termination Date, the Company is no longer be eligible to receive milestone payments or royalties in association with the terminated programs.

Under the terms of the 2022 Novartis Agreement, Novartis paid the Company an upfront payment of $54.0 million. Effective as of March 1, 2023, Novartis exercised its Novartis License Options to license TRACER Capsids for use in gene therapy programs against two undisclosed Initial Novartis Targets. With Novartis’ option exercise on two Initial Novartis Targets, the Company received a $25.0 million option exercise payment in April 2023. Novartis paid the Company a one-time fee of $15.0 million in consideration for the rights granted under the Novartis Amendment, which the Company received in October 2024.

The Company is eligible to receive specified development, regulatory, and commercialization milestone payments of up to an aggregate of $125.0 million for the first Novartis Initial Licensed Product for each Initial Novartis Target for which a Novartis License Option has been exercised to achieve the corresponding milestone. Following the partial termination of the 2022 Novartis Option and License Agreement by Novartis in October 2025, the 2022 Novartis Option and License Agreement remains active with respect to one gene therapy program forone Initial Novartis Target. The Company is eligible to receive (a) specified sales milestone payments of up to an aggregate of $175.0 million per Novartis Initial Licensed Product directed to the Initial Novartis Target and (b) tiered, escalating royalties in the mid- to high-single-digit percentages based on annual net sales of each Novartis Initial Licensed Product directed to the Initial Novartis Target.

Unless earlier terminated, the 2022 Novartis Agreement expires on the expiration of the last-to-expire royalty term with respect to all Novartis Licensed Products in all countries. Novartis may terminate the 2022 Novartis Agreement, in whole or in part, for any or no reason upon ninety days’ written notice to the Company. The 2022 Novartis Agreement may also be terminated by either party under specific circumstances, including the other party’s uncured material breach.

Upon certain terminations for cause by Novartis, the licenses granted by the Company to Novartis under the 2022 Novartis Agreement shall become irrevocable and perpetual, and all milestone payments and royalties that would have otherwise been payable by Novartis under such licenses had the Novartis Agreement remained in effect would be substantially reduced.

At inception, the Company determined the 2022 Novartis Agreement was a contract with a customer under ASC 606. The Company assessed the promised goods and services and determined that the 2022 Novartis Agreement contains three performance obligations consisting ofthree material rights, one for each of the Novartis License Options. The Company concluded that each Novartis License Option provides a material right as consideration for each option is less than the amount that the Company would otherwise have expected to receive outside the context of the contract. The promises at inception do not include the underlying goods or services that would be delivered upon exercise of the option but rather represent the value to the customer of having the right to exercise the Novartis License Option at the specified exercise fee.

The Company received a nonrefundable, upfront payment of $54.0 million as consideration under the 2022 Novartis Agreement, which represents the transaction price at inception. Additional consideration to be paid to the Company upon exercise of the Novartis License Options or upon reaching certain milestones are excluded from the transaction price as they relate to option fees and milestones that could only be achieved subsequent to an option exercise.

The Company allocated the transaction price to thethree material rights based on their relative standalone selling prices. The estimated standalone selling price for each material right was based on an adjusted market assessment approach. The Company concluded that the market would be willing to pay an equal amount for each Novartis License Option on a standalone basis. The Company reached this conclusion after considering (i) the downstream economics including option fees, milestones and royalties related to each Novartis License Option being identical and (ii)

comparable market data. Based on the relative standalone selling price for each of thethree material rights, the allocation of the transaction price to the separate performance obligations is $18.0 million for each material right. The amount allocated to each material right was recorded as deferred revenue and recognized as revenue during the year ended December 31, 2023.

Novartis agreed to pay to the Company a one-time fee of $15.0 million in consideration for the rights granted under the Novartis Amendment, which was received in October 2024. The Company evaluated the Novartis Amendment under ASC 606 and recorded $15.0 million as collaboration revenue during the year ended December 31, 2024, since the consideration reflected the standalone selling price of the license that was delivered on the Novartis Amendment date, and there were no remaining undelivered performance obligations under the original 2022 Novartis Agreement.

The Company is eligible to receive specified development, regulatory, and commercialization milestone payments of up to an aggregate of $125.0 million for the Initial Novartis Target. The Company is also eligible to receive (a) specified sales milestone payments of up to an aggregate of $175.0 million per Novartis Initial Licensed Product directed to the Initial Novartis Target and (b) tiered, escalating royalties in the mid- to high-single-digit percentages based on annual net sales of each Novartis Initial Licensed Product directed to the Initial Novartis Target.

The termination in October 2025 has no impact on the transaction price of the 2022 Novartis Agreement as all variable consideration under the 2022 Novartis Agreement was previously constrained.

The Company didnot recognize any revenue under the 2022 Novartis Agreement during the year ended December 31, 2025. During the year ended December 31, 2024, the Company recognized $15.0 million of collaboration revenue related to the Novartis Amendment from the one-time fee received in October 2024 discussed above.

During the year ended December 31, 2023, the Company recognized $79.0 million in collaboration revenue related to the 2022 Novartis Agreement. Of this $79.0 million, $54.0 million is attributable to material rights discussed above. The remaining $25.0 million represents the option exercise fee, which was received by the Company during the second quarter of 2023.

2023 Neurocrine Collaboration Agreement

In January 2023, the Company entered into a collaboration and license agreement with Neurocrine (the “2023 Neurocrine Collaboration Agreement”) for the research, development, manufacture and commercialization of gene therapy products designed to address PD and glucosylceramidase beta 1-mediated diseases (the “GBA1 Program”), and three new programs focused on the research, development, manufacture and commercialization of gene therapies designed to address CNS diseases or conditions associated with rare genetic targets (the “2023 Discovery Programs” and, collectively with the GBA1 Program, the “2023 Neurocrine Programs”). The 2023 Neurocrine Collaboration Agreement became effective on February 21, 2023 (the “Neurocrine Effective Date”).

Under the 2023 Neurocrine Collaboration Agreement, the Company and Neurocrine have agreed to collaborate on the conduct of the 2023 Neurocrine Programs. Subject to the rights retained by the Company under the 2023 Neurocrine Collaboration Agreement, the Company granted to Neurocrine, as of the Neurocrine Effective Date, an exclusive, royalty-bearing, sublicensable, worldwide license, under certain of the Company’s intellectual property rights, to research, develop, manufacture and commercialize gene therapy products (the “2023 Collaboration Products”), arising under the 2023 Neurocrine Programs.

Pursuant to mutually-agreed development plans, during the period beginning on the Neurocrine Effective Date and ending on the third anniversary of the Neurocrine Effective Date (the “2023 Discovery Period”), and as overseen by the Joint Steering Committee for the ongoing collaboration with Neurocrine, the Company was responsible for identifying capsids meeting target criteria, producing development candidates, and conducting other pre-clinical

activities regarding the 2023 Collaboration Products. The 2023 Discovery Period expired on February 21, 2026. With the exception of one preclinical study where the Company agreed to share costs, Neurocrine has agreed to be responsible for all costs the Company incurs in conducting pre-clinical development activities for each 2023 Neurocrine Program, in accordance with JSC agreed upon workplans and budgets. If the Company breaches its responsibilities during this time or, in certain circumstances, upon a change of control, Neurocrine has the right, but not the obligation, to assume the conduct of the Company’s activities under such 2023 Neurocrine Program.

The Company has been granted the option (“2023 Co-Co Option”) to co-develop and co-commercialize 2023 Collaboration Products in the GBA1 Program in the United States upon the occurrence of a specified event (“2023 Co-Co Trigger Event”). Should the Company elect to exercise its 2023 Co-Co Option, the Company and Neurocrine agree to enter into a cost and profit-sharing arrangement (a “2023 Co-Co Agreement”), whereby the Company and Neurocrine agree to jointly develop and commercialize 2023 Collaboration Products in the GBA1 Program (“2023 Co-Co Products”) in the United States and share equally in the GBA1 Program’s costs, profits and losses in the United States, with each party entitled to or responsible for 50% of profits and losses with respect to each 2023 Co-Co Product in the United States, subject to specified exceptions. The parties have agreed that the 2023 Co-Co Agreement will provide the Company the right to terminate the 2023 Co-Co Agreement for any reason upon prior written notice to Neurocrine and provide Neurocrine the right to terminate or amend the 2023 Co-Co Agreement upon a change of control under certain circumstances. In the event the Company exercises its 2023 Co-Co Option, the parties have also agreed that Neurocrine is entitled to receive (in addition to its 50% share of profits)50% of the Company’s share of profits until the Company’s obligation to repay 50% of all development costs incurred by Neurocrine in connection with the GBA1 Program prior to such exercise have been paid off. The 2023 Co-Co Trigger Event is the date on which the Company receives topline data from the first clinical trial for a product candidate being developed for PD pursuant to the GBA1 Program or if none, then another indication under the GBA1 Program.

Candidate Selection

Either party may notify the JSC of any gene therapy product candidate that includes a Company capsid and a payload that is being developed under a 2023 Neurocrine Program (a “Collaboration Candidate”), that it desires to nominate as a development candidate. In such event, the JSC shall determine whether such nominated Collaboration Candidate meets certain development criteria. There will be a maximum offour potential development candidates for which development is being performed under any 2023 Neurocrine Program at any given time during the 2023 Discovery Period, which expired in February 2026. If a Collaboration Candidate fails to meet criteria established by the JSC and is removed from consideration to become a development candidate or is named a development candidate, then a new Collaboration Candidate may be nominated to be a potential development candidate to replace the Collaboration Candidate that has failed or succeeded such that not more than four potential development candidates per program are under consideration at any one time during the 2023 Discovery Period.

The parties have agreed that the applicable development plans shall specify the allocation between the Company and Neurocrine of responsibilities for the manufacturing of Collaboration Candidates associated with the applicable 2023 Neurocrine Program during the 2023 Discovery Period. In accordance with the 2023 Collaboration Agreement, the parties have also agreed that, if the Company conducts any portion of the manufacturing of a Collaboration Candidate, the applicable development plan shall include an obligation for the Company to assist with the technology transfer of such manufacturing responsibilities to Neurocrine or a third-party contract manufacturing organization, as reasonably requested by Neurocrine, on terms to be mutually-agreed by the Company and Neurocrine. Following the end of the 2023 Discovery Period, which expired in February 2026, Neurocrine shall be responsible for the manufacturing of all Collaboration Candidates and products.

Under the terms of the 2023 Neurocrine Collaboration Agreement, Neurocrine paid the Company an upfront payment of approximately $136.0 million and approximately $39.0 million for the purchase of 4,395,588 shares of common stock of the Company at a price of $8.88 per share in February 2023. The 2023 Collaboration Agreement

provides for aggregate development milestone payments from Neurocrine to the Company for 2023 Collaboration Products under (a) the GBA1 Program of up to $985.0 million; and (b) each of thethree 2023 Discovery Programs of up to $175.0 million for each 2023 Discovery Program. The Company may be entitled to receive aggregate commercial milestone payments for up totwo 2023 Collaboration Products under the GBA1 Program of up to $950.0 million per 2023 Collaboration Product and forone 2023 Collaboration Product under each 2023 Discovery Program of up to $275.0 million per 2023 Discovery Program. The Company agreed to a forfeit certain milestones and royalties on net sales in the United States if the Company exercises the 2023 Co-Co Option. The JSC’s selection of the development candidate for the GBA1 Program in April 2024 triggered a $3.0 million milestone payment, which the Company received in May 2024. Additionally, the JSC’s selection of the development candidate for a 2023 Discovery Program in September 2024 triggered a $3.0 million milestone payment, which the Company received in October 2024. An additional development candidate for a 2023 Discovery Program was selected by the JSC in October 2025, triggering another $3.0 million milestone payment, which was received in November 2025.

Neurocrine has also agreed to pay the Company tiered royalties, based on future net sales of the 2023 Collaboration Products. Such royalty percentages, for net sales in and outside the United States, range from (a) for the GBA1 Program, the low double-digits to twenty and the high single-digits to mid-teens, respectively, and (b) for each 2023 Discovery Program, high single-digits to mid-teens and mid-single digits to low double-digits, respectively. On a country-by-country and 2023 Neurocrine Program-by-2023 Neurocrine Program basis, the parties have agreed royalty payments would commence on the first commercial sale of a 2023 Collaboration Product in such country and terminate upon the latest of (a) the expiration, invalidation or the abandonment of the last patent covering the composition of the 2023 Collaboration Product or its approved method of use in such country, (b)ten years from the first commercial sale of the 2023 Collaboration Product in such country and (c) the expiration of regulatory exclusivity in such country (the “2023 Royalty Term”). Royalty payments may be reduced by up to 50% in specified circumstances, including expiration of patent rights related to a 2023 Collaboration Product, approval of biosimilar products in a given country, or required payment of licensing fees to third parties related to the development and commercialization of any 2023 Collaboration Product. Additionally, the licenses granted to Neurocrine shall automatically convert to a fully-paid, perpetual, irrevocable royalty-free license on a country-by-country and 2023 Collaboration Product-by-2023 Collaboration Product basis upon the expiration of the 2023 Royalty Term applicable to the 2023 Collaboration Product in such country.

Unless earlier terminated, the 2023 Neurocrine Collaboration Agreement expires on the later of (a) the expiration of the last-to-expire 2023 Royalty Term with respect to all 2023 Collaboration Products worldwide or (b) the expiration or termination of any 2023 Co-Co Agreement. Neurocrine may terminate the 2023 Neurocrine Collaboration Agreement in its entirety or on a 2023 Neurocrine Program-by-2023 Neurocrine Program and/or country-by-country basis by providing at least (a) 180-day advance notice if such notice is provided prior to the first commercial sale of any 2023 Collaboration Product to which the termination applies or (b) one-year advance notice if such notice is provided after the first commercial sale of any product to which the termination applies. The 2023 Neurocrine Collaboration Agreement may also be terminated by either party under specific circumstances, including the other party’s uncured material breach.

2023 Neurocrine Stock Purchase Agreement

In connection with the execution of the 2023 Neurocrine Collaboration Agreement, Neurocrine and the Company also entered into a stock purchase agreement on January 8, 2023 (“the “2023 Neurocrine Stock Purchase Agreement”), for the sale and issuance of 4,395,588 shares of common stock to Neurocrine at a price of $8.88 per share, for an aggregate purchase price of approximately $39.0 million. In accordance with the terms and conditions of the 2023 Neurocrine Stock Purchase Agreement, the Company issued and sold these shares to Neurocrine in February 2023.

At inception, the Company determined the 2023 Neurocrine Collaboration Agreement was a contract with a customer under ASC 606 and that modification accounting was not required given that the 2023 Neurocrine Collaboration Agreement did not modify the scope or price of the 2019 Neurocrine Collaboration Agreement. The

Company therefore determined that the 2023 Neurocrine Agreement should be accounted for separately. The 2023 Neurocrine Collaboration Agreement includes the following performance obligations: (i) the development and commercialization license for the GBA1 Program, (ii) the research and development services for the GBA1 Program, and (iii) the research and development services for each of the 2023 Discovery Programs combined with a development and commercialization license for each program. The license for the GBA1 Program is distinct as Neurocrine can benefit from such license on its own or from other resources commonly available in the industry given the stage of development of the product candidates subject to the license. Similarly, the research and development services for the GBA1 Program provide a distinct benefit to Neurocrine within the context of the contract, separate from the license. The research and development services for the 2023 Discovery Programs are not distinct as Neurocrine cannot benefit from such licenses on its own or from other resources commonly available in the industry, without the corresponding research services due to the unique and specialized expertise of the Company that is not readily available in the marketplace. The GBA1 license, GBA1 research and development services and the combined licenses and research and development services for the 2023 Discovery Programs are distinct from one another as Neurocrine can benefit from each program separately.

The Company identified $143.9 million of fixed transaction price consisting of the $136.0 million upfront fee, and a premium of $7.9 million related to the $39.0 million equity investment of 4,395,588 shares when measured at fair value on the date of issuance. The Company is also entitled to reimbursement of costs incurred by the Company during the 2023 Discovery Period associated with each of the GBA1 Program and 2023 Discovery Programs.

These amounts are determinable based on development plans, and the Company has a contractual right to the payment of costs incurred under the agreed upon program development plans.

The Company utilizes the most likely amount approach to estimate the cost reimbursement and has concluded this consideration should be constrained. As of December 31, 2025, the Company’s estimate of total variable consideration under the arrangement was $9.8 million. Substantially all of this amount has been recognized as of December 31, 2025. The sales milestone payments and royalties will be recognized in the period the underlying sales occur, as this consideration is related to thetwo development and commercialization licenses, the predominant performance obligations in the contract.

The Company has allocated the fixed transaction price to the separate performance obligations based on the relative standalone selling price of each performance obligation. The estimated standalone selling prices for performance obligations were developed using the estimated selling price of the license for the GBA1 Program and each of the three 2023 Discovery Programs, using primarily adjusted market assessment approaches that considered discounted, probability-weighted cash flow analyses and entity-specific and market factors. The Company did not allocate any of the fixed transaction price to the GBA1 research and development services performance obligation as the consideration for such services reflects a market rate.

The Company concluded that the variable consideration related to the cost reimbursement of each program will be allocated to each respective program as the cost reimbursement relates specifically to the respective program services being performed under the 2023 Neurocrine Collaboration Agreement. The reimbursement of research services is at a market rate and the allocation of the fixed consideration to each of thethree 2023 Discovery Program performance obligations depicts the estimated amounts in which it would expect to receive for these obligations, absent the variable consideration related to the research reimbursement.

In April 2024, the JSC with Neurocrine selected a development candidate for the GBA1 program under the 2023 Neurocrine Collaboration Agreement. The JSC’s selection of a development candidate for the GBA1 Program triggered a $3.0 million milestone payment to the Company. The Company recorded the $3.0 million as collaboration revenue during the second quarter of 2024.

In September 2024, the JSC with Neurocrine selected a development candidate in a gene therapy program for the potential treatment of an undisclosed neurological disease under the 2023 Neurocrine Collaboration Agreement, which triggered a $3.0 million milestone payment to the Company. The Company included the $3.0 million that had previously been constrained in the transaction price allocated to the program’s performance obligation in the three

months ended September 30, 2024, which resulted in a cumulative catch-up adjustment to collaboration revenue of approximately $2.0 million.

In October 2025, the JSC with Neurocrine selected an additional development candidate in a gene therapy program under the 2023 Neurocrine Collaboration Agreement, triggering another $3.0 million milestone payment, which was received in November 2025. Of this amount, $2.8 million was recognized as collaboration revenue during the fourth quarter of 2025 and the remaining $0.2 million was recognized as deferred revenue as of December 31, 2025.

The Company recognized the fixed transaction price allocated to the development and commercialization license for the GBA1 Program as collaboration revenue in the first quarter of 2023, upon delivery of the development and commercialization license for the GBA1 Program to Neurocrine. The Company is recognizing the consideration allocated to each of the three 2023 Discovery Program performance obligations on a proportional performance basis over the period of service using input-based measurements such as costs incurred to date, to estimate proportion performed, and remeasures its progress towards completion at the end of each reporting period. Proportional performance is determined based on the workplan cost and timeline estimates.

During the year ended December 31, 2025, the Company recognized $26.5 million of collaboration revenue associated with the fixed transaction price allocated to thethree 2023 Discovery Programs, $2.8 million of collaboration revenue associated with the selection of a development candidate for an additional development program, and $1.2 million of collaboration revenue associated with research and development services performed during the period and the corresponding cost reimbursement receivable. As of December 31, 2025, there was $1.3 million of deferred revenue related to the 2023 Neurocrine Collaboration Agreement, all of which was classified as current in the accompanying balance sheets based on the period the services are expected to be delivered. Additionally, as of December 31, 2025, there was $0.1 million of related party collaboration receivable related to reimbursable costs expected to be received from Neurocrine for research and development services performed.

During the year ended December 31, 2024, the Company recognized $44.5 million of collaboration revenue associated with the fixed transaction price allocated to thethree 2023 Discovery Programs, $3.0 million of collaboration revenue associated with the selection of a development candidate for the GBA1 Program, and $2.2 million of collaboration revenue associated with research and development services performed during the period and the corresponding cost reimbursement receivable. As of December 31, 2024, there was $27.6 million of deferred revenue related to the 2023 Neurocrine Collaboration Agreement, of which $22.3 million was classified as current and $5.3 million was classified as non-current in the accompanying balance sheets based on the period the services are expected to be delivered. Additionally, as of December 31, 2024, there was $0.3 million of related party collaboration receivable related to reimbursable costs expected to be received from Neurocrine for research and development services performed.

During the year ended December 31, 2023, the Company recognized $69.5 million of revenue associated with the 2023 Neurocrine Collaboration Agreement related to the delivery of the development and commercialization license for the GBA1 Program. During the year ended December 31, 2023, the Company recognized $5.8 million of collaboration revenue associated with research and development services performed during the period and the corresponding cost reimbursement receivable for the GBA1 Program. During the year ended December 31, 2023, the Company recognized a total of $5.5 million of revenue associated with the fixed transaction price allocated to thethree 2023 Discovery Programs, and for research and development services performed during the period.

The Company incurred approximately $0.4 million of costs to obtain the 2023 Neurocrine Collaboration Agreement which were payable only upon the close of the transaction and therefore considered incremental costs of obtaining a contract with a customer and capitalized. The costs are recorded in prepaid expenses and are being amortized to operating expenses consistent with the manner in which the consideration allocated to the performance obligations is recognized.

2019 Neurocrine Collaboration Agreement

Effective March 2019, the Company entered into a collaboration agreement with Neurocrine (the “2019 Neurocrine Collaboration Agreement”) for the research, development and commercialization of certain of its AAV gene therapy products. Under the 2019 Neurocrine Collaboration Agreement, the Company agreed to collaborate on the conduct of four collaboration programs (the “2019 Neurocrine Programs”) which include: (a) VY-AADC (NBIb-1817) for PD (the “VY-AADC Program”), (b) a program for the treatment of FA (the “FA Program” and, collectively with the VY-AADC Program, the “Legacy Programs”), and (c) two programs to be determined by the Company and Neurocrine at a later date (the “2019 Discovery Programs”).

In February 2021, Neurocrine notified the Company that it had elected to terminate the 2019 Neurocrine Collaboration Agreement solely with regards to the VY-AADC Program, effective August 2, 2021. As a result of the termination, Neurocrine is no longer obligated to reimburse the Company for research and development activities related to the VY-AADC Program and the Company is no longer eligible to receive milestone or royalty payments related to the VY-AADC Program.

On April 30, 2025, as a result of Neurocrine no longer prioritizing thetwo 2019 Discovery Programs, the JSC mutually agreed to discontinue the activities associated with such programs, and to return the rights to the undisclosed targets to the Company. As a result of the discontinuation, the licenses granted by the Company to Neurocrine with respect to the 2019 Discovery Programs terminated and the Company regained worldwide intellectual property rights regarding such programs. Additionally, Neurocrine is no longer obligated to reimburse the Company for research and development activities related to thetwo 2019 Discovery Programs and the Company is no longer eligible to receive milestone or royalty payments related to thetwo 2019 Discovery Programs. The 2019 Neurocrine Collaboration Agreement remains in full force and effect for the FA Program.

Under the terms of the 2019 Neurocrine Collaboration Agreement, the Company has agreed to collaborate with Neurocrine on, and to grant, exclusive, royalty-bearing, non-transferable, sublicensable licenses to certain of its intellectual property rights, for all human and veterinary diagnostic, prophylactic, and therapeutic uses, for the research, development, and commercialization of gene therapy products (the “2019 Collaboration Products”) under the FA Program in the United States and, all countries in the world in which the 2019 Neurocrine Collaboration Agreement remains in effect with respect to the FA Program. As a result of the termination of the 2019 Neurocrine Collaboration Agreement with regards to the VY-AADC Program and the mutual JSC decision to discontinue the activities associated with thetwo undisclosed programs, in accordance with the terms of the 2019 Neurocrine Collaboration Agreement, the licenses granted by the Company to Neurocrine regarding the VY-AADC Program and thetwo undisclosed programs have expired, and the Company has regained worldwide intellectual property rights regarding the VY-AADC Program and thetwo undisclosed programs, in each case as of the corresponding Termination Effective Dates.

Pursuant to development plans agreed by the parties, which are overseen by a JSC, the Company has operational responsibility, subject to certain exceptions, for the conduct of each 2019 Neurocrine Program prior to the occurrence of a specified event for such 2019 Neurocrine Program (a “2019 Transition Event”), as described below, and is required to use commercially reasonable efforts to develop the corresponding 2019 Collaboration Products. Neurocrine has agreed to be responsible for all costs incurred by the Company in conducting these activities for each 2019 Neurocrine Program, in accordance with an agreed budget for each 2019 Neurocrine Program. If the Company breaches its development responsibilities or in certain circumstances upon a change in control, Neurocrine has the right but not the obligation to assume the activities under such 2019 Neurocrine Program.

Upon the occurrence of a 2019 Transition Event for each 2019 Neurocrine Program, Neurocrine has agreed to assume responsibility for development, manufacturing and commercialization activities for such 2019 Neurocrine Program from the Company and to pay milestones and royalties on future net sales as described further below. For the FA Program, the Company was granted the option (the “2019 Co-Co Option”) to co-develop and co-commercialize the

FA Program upon the occurrence of a specified event (the “2019 Co-Co Trigger Event”). The Company agreed, were the Company to exercise the 2019 Co-Co Option, to enter into a cost- and profit-sharing arrangement with Neurocrine (the “2019 Co-Co Agreement”), and (a) jointly develop and commercialize 2019 Collaboration Products for the FA Program (“2019 Co-Co Products”), (b) share in its costs, profits and losses, and (c) forfeit certain milestones and royalties on net sales in the United States during the effective period of the 2019 Co-Co Agreement. The 2019 Transition Event with respect to the FA Program is the Company’s receipt of topline data for the initial Phase 1 clinical trial for an FA Program product candidate. The 2019 Co-Co Trigger Event is the achievement of milestones or metrics specified in the applicable development plan, as determined by the JSC.

Under the 2019 Neurocrine Collaboration Agreement, subject to exceptions specified therein, the Company and Neurocrine agreed that profits and losses under the Company’s 2019 Co-Co Option would be allocated 60% to Neurocrine and 40% to the Company for any FA Collaboration Product. The parties agreed that 2019 Co-Co Agreement would provide the Company the right to terminate for any reason upon prior written notice to Neurocrine and Neurocrine the right to terminate in certain circumstances upon change of control.

The Company’s research and development activities under the 2019 Neurocrine Collaboration Agreement are conducted pursuant to plans agreed to by the parties, on a program-by-program basis, and overseen by the JSC, as detailed in the 2019 Neurocrine Collaboration Agreement.

The 2019 Neurocrine Collaboration Agreement provides for an upfront non-refundable payment of $115.0 million, as well as for aggregate development and regulatory milestone payments from Neurocrine to the Company for 2019 Collaboration Products under the FA Program of up to $195.0 million. The Company may be entitled to receive aggregate commercial milestone payments for each 2019 Collaboration Product of up to $275.0 million, for a total of up to $550.0 million under the FA Program. The JSC’s selection of the development candidate for the FA Program in February 2024 triggered a $5.0 million milestone payment, which the Company received in March 2024. Furthermore, in connection with the 2019 Neurocrine Collaboration Agreement, Neurocrine purchased 4,179,728 shares of the Company’s common stock at a price of $11.9625 per share, for an aggregate purchase price of $50.0 million.

Neurocrine also agreed to pay the Company royalties, based on future net sales of the 2019 Collaboration Products. Such royalty percentages, for net sales in and outside the United States, as applicable, range from the low-teens to high-teens and high-single digits to mid-teens for the FA Program. On a country-by-country and program-by-program basis, royalty payments would commence on the first commercial sale of a 2019 Collaboration Product and terminate on the later of (a) the expiration of the last patent covering the 2019 Collaboration Product or its method of use in such country, (b)ten years from the first commercial sale of the 2019 Collaboration Product in such country and (c) the expiration of regulatory exclusivity in such country (the “2019 Royalty Term”). Royalty payments may be reduced by up to 50% in specified circumstances, including expiration of patents rights related to a 2019 Collaboration Product, approval of biosimilar products in a given country or required payment of licensing fees to third parties related to the development and commercialization of any 2019 Collaboration Product. Additionally, the licenses granted to Neurocrine shall automatically convert to fully paid-up, non-royalty bearing, perpetual, irrevocable, exclusive licenses on a country-by-country and product-by-product basis upon the expiration of the 2019 Royalty Term applicable to such 2019 Collaboration Product in such country.

Unless earlier terminated, the 2019 Neurocrine Collaboration Agreement expires on the later of (a) the expiration of the last to expire 2019 Royalty Term with respect to a 2019 Collaboration Product in all countries in the relevant territory or (b) the expiration or termination of any 2019 Co-Co Agreement. Neurocrine may terminate the 2019 Neurocrine Collaboration Agreement in its entirety or on a program-by-program or country-by-country basis by providing at least (x) 180-day advance notice if such notice is provided prior to the first commercial sale of the 2019 Collaboration Product to which the termination applies or (y) one-year advance notice if such notice is provided after the first commercial sale of the 2019 Collaboration Product to which the termination applies. The 2019 Neurocrine

Collaboration Agreement may also be terminated by either party under specific circumstances, including the other party’s uncured material breach.

At inception, the Company determined the 2019 Neurocrine Collaboration Agreement was a contract with a customer under ASC 606, and included the following performance obligations: (a) research and development services for each Legacy Program combined with a development and commercialization license for each such program and (b) research and development services for each 2019 Discovery Program combined with a development and commercialization license for each program. The research services and license on a program-by-program basis are not distinct as Neurocrine cannot benefit from such license on its own or from other resources commonly available in the industry, without the corresponding research services due to the unique and specialized expertise of the Company that is not readily available in the marketplace.

The Company identified $97.4 million of fixed transaction price consisting of the $115.0 million upfront fee, $5.0 million payment from the June 2019 Modification and $5.0 million payment from the selection of a lead development candidate in February 2024, offset by a discount of $27.6 million related to the $50.0 million equity investment of 4,179,728 shares when measured at fair value on the date of issuance. The Company is also entitled to reimbursement of costs incurred by the Company prior to the 2019 Transition Events associated with each 2019 Neurocrine Program. These amounts are determinable based on program plans and budgets, and the Company has a contractual right to the payment of cost incurred under the agreed upon program plans. The Company utilized the most likely amount approach and estimated the expected cost reimbursement to be $431.1 million at inception. The Company concluded that these amounts do not require a constraint and are included in the transaction price at inception. The Company considers this estimate at each reporting date and updates the estimate based on information available. As of December 31, 2025, the Company estimates the total variable consideration from expected reimbursements to be $82.1 million, which is based on expectations resulting from decisions made during JSC meetings. Substantially all of this amount has been recognized as of December 31, 2025. Additional consideration to be paid to the Company upon reaching certain milestones are excluded from the transaction price at inception due to the uncertainty of achieving the development and regulatory milestones.

The Company allocated the fixed transaction price to the separate performance obligations based on the relative standalone selling price of each performance obligation or in the case of certain variable consideration to one or more performance obligations. The estimated standalone selling prices for performance obligations, which include a license and research services, were developed using the estimated selling price of the license, using comparable and market data, and an estimate of the overall effort to perform the research services along with a reasonable profit for research services.

In February 2024, the JSC with Neurocrine selected a lead development candidate for the FA Program under the 2019 Neurocrine Collaboration Agreement, which triggered a $5.0 million milestone payment to the Company that was received in the first quarter of 2024. The Company included the $5.0 million that had previously been constrained in the transaction price allocated to the FA Program performance obligation in the three months ended March 31, 2024, accordingly, which resulted in a cumulative catch-up adjustment to collaboration revenue of $4.4 million.

The Company recognizes the transaction price associated with each performance obligation on a proportional performance basis over the period of service using input-based measurements such as costs incurred to date, to estimate proportion performed, and remeasures its progress towards completion at the end of each reporting period.

During the years ended December 31, 2025, 2024, and 2023, the Company recognized $3.5 million, $10.4 million, and $9.8 million of revenue, respectively, associated with its collaboration with Neurocrine related to fixed transaction price allocated to the active programs, and research and development services performed during the period and the corresponding cost reimbursement receivable.

As of December 31, 2025, there was $0.3 million of deferred revenue related to the 2019 Neurocrine Collaboration Agreement, all of which is classified as current in the accompanying consolidated balance sheet based on the period the services are expected to be delivered. Additionally, as of December 31, 2025, there was $0.1 million of

collaboration receivable related to reimbursable costs expected to be received from Neurocrine for research and development services performed.

As of December 31, 2024, there was $2.8 million of deferred revenue related to the 2019 Neurocrine Collaboration Agreement, which is classified as either current or non-current in the accompanying consolidated balance sheet based on the period the services are expected to be delivered. Additionally, as of December 31, 2024, there was $0.4 million of collaboration receivable related to reimbursable costs expected to be received from Neurocrine for research and development services performed.

The following table presents changes in the balances of the Company’s related party collaboration receivable and contract liabilities for both the 2023 Neurocrine Collaboration Agreement and the 2019 Neurocrine Collaboration Agreement during the year ended December 31, 2025:

The change in the related party collaboration receivable balance for the year ended December 31, 2025 is primarily driven by amounts owed to the Company for research and development services provided, offset by amounts collected from Neurocrine during the period, for both the 2023 Neurocrine Collaboration Agreement and the 2019 Neurocrine Collaboration Agreement.

Deferred revenue activity for the year ended December 31, 2025, includes the $31.8 million of collaboration revenue recognized on the proportional performance model during the year ended December 31, 2025, for both the 2023 Neurocrine Collaboration Agreement and 2019 Neurocrine Collaboration Agreement.

Alexion Option and License Agreement (Formerly Pfizer Option and License Agreement)

The Company is party to an option and license agreement with Alexion (the “Alexion Agreement”). The Company initially entered into the Alexion Agreement with Pfizer, Inc. (“Pfizer”) in October 2021 (the “Alexion Agreement Effective Date”). However, Alexion (via Alexion Pharma International Operations Limited (“APIO”)) later acquired all of Pfizer’s rights under the Alexion Agreement and became the successor-in-interest to Pfizer thereunder effective upon the closing of a definitive purchase and license agreement between Pfizer and Alexion in September 2023. APIO subsequently assigned the Alexion Agreement to its affiliate AstraZeneca Ireland Limited (“AstraZeneca”). Neither the acquisition by Alexion nor the subsequent assignment from APIO to AstraZeneca impacted the material terms of the Alexion Agreement. Pursuant to the Alexion Agreement, the Company has granted Alexion an exclusive, worldwide license, with the right to sublicense, under certain of its intellectual property, the rights to develop and commercialize AAV gene therapy products for the potential treatment of a rare neurological disease comprised of a TRACER Capsid (the “Alexion Licensed Capsid”), and a specified transgene (the “Alexion Transgene”). Such AAV gene therapy products are referred to as “Alexion Licensed CNS Products.”

Prior to Alexion’s acquisition of all of Pfizer’s rights under the Alexion Agreement, the Company had granted Pfizer the right to exercise up totwo options to license TRACER Capsids to develop and commercialize certain AAV gene therapy candidates comprised of a TRACER capsid and a specified transgene. In September 2022, Pfizer exercised its option with respect to a TRACER Capsid for a specified transgene for potential treatment of a rare neurological disease. All of Pfizer’s rights in connection with such option exercise were transferred to Alexion as discussed above. Pfizer did not exercise its option with respect to any TRACER Capsid for a specified transgene for the potential treatment of a cardiovascular disease. As result, all rights to any TRACER Capsids for that cardiovascular disease reverted to the Company in accordance with the terms of the Alexion Agreement.

Prior to Pfizer’s transfer of its rights under the Alexion Agreement, Pfizer paid the Company an upfront payment of $30.0 million in October 2021, and an additional fee of $10.0 million in connection with its exercise of an option. The Company is also eligible to receive specified development, regulatory, and commercialization milestone payments of up to an aggregate of $115.0 million for the first corresponding Alexion Licensed CNS Product to achieve the corresponding milestone. On an Alexion Licensed CNS Product-by-Alexion Licensed CNS Product basis, the Company is also eligible to receive (a) specified sales milestone payments of up to an aggregate of $175.0 million per Alexion Licensed CNS Product and (b) tiered, escalating royalties in the mid- to high-single-digit percentages of annual net sales of each Alexion Licensed CNS Product. The royalties are subject to potential reductions in customary circumstances including patent claim expiration, payments for certain third-party licenses, and biosimilar market penetration, subject to specified limits.

Unless earlier terminated, the Alexion Agreement expires on the expiration of the last-to-expire royalty term with respect to all Alexion Licensed CNS Products in all countries. Alexion may also terminate the Alexion Agreement, in whole or in part, for any or no reason upon ninety days’ written notice to the Company. The Alexion Agreement may also be terminated by either party under specific circumstances, including the other party’s uncured material breach.

Upon certain terminations for cause by Alexion, the license that the Company has granted to Alexion under the Alexion Agreement shall become irrevocable and perpetual, and all milestone payments and royalties that would have otherwise been payable by Alexion under such license had the Alexion Agreement remained in effect would be substantially reduced.

At inception, the Company determined the Alexion Agreement was a contract with a customer under ASC 606. The Company assessed the promised goods and services under the Alexion Agreement, in accordance with ASC 606, and determined that the Alexion Agreement containstwo performance obligations consisting oftwo material rights, one for each of the options to license a TRACER Capsid.

The Company received a nonrefundable, upfront payment of $30.0 million as consideration under the Alexion Agreement, which represented the transaction price at inception.

The Company allocated the transaction price to the options based on their relative standalone selling prices, or $15.0 million for each material right, both of which were recognized during the year ended December 31, 2022.

No revenue was recognized under the Alexion Agreement for the years ended December 31, 2025, 2024, and 2023.

10. Common stock

As of December 31, 2025, and 2024, the Company had authorized 120,000,000 shares of common stock, at $0.001 par value per share.

The voting, dividend and liquidation rights of the holders of the common stock are subject to and qualified by the rights, powers and preferences of the holders of preferred stock.

The holders of shares of common stock are entitled to share ratably in the Company’s remaining assets available for distribution to its stockholders in the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company or upon occurrence of a deemed liquidation event.

Shares Reserved for Future Issuance

11. Stock-based compensation

2014 Stock Option and Grant Plan

In January 2014, the Company adopted the 2014 Stock Option and Grant Plan (the “2014 Plan”), under which it could grant incentive stock options, non-qualified stock options, restricted stock awards, unrestricted stock awards, or restricted stock units to purchase up to 823,529 shares of common stock to employees, officers, directors and consultants of the Company.

The terms of stock option agreements, including vesting requirements, were determined by the board of directors and were subject to the provisions of the 2014 Plan. Restricted stock awards granted by the Company generally vest based on each grantee’s continued service with the Company during a specified period following grant. Stock options granted to employees generally vest over four years, with 25% vesting on theone-year anniversary and 75% vesting ratably, on a monthly basis, over the remaining three years. Stock options granted to non-employee consultants generally vest monthly over a period ofone tofour years.

2015 Stock Option Plan

In October 2015, the Company’s board of directors and stockholders approved the 2015 Stock Option and Incentive Plan (“2015 Stock Option Plan”), which became effective upon the completion of the Company’s initial public offering (“IPO”). The 2015 Stock Option Plan provides the Company with the flexibility to use various equity-based incentive and other awards as compensation tools to motivate its workforce. These tools include stock options, stock appreciation rights, restricted stock, restricted stock units, unrestricted stock, performance share awards and cash-based awards. The 2015 Stock Option Plan replaced the 2014 Plan. Any options or awards outstanding under the 2014 Plan remained outstanding and effective. The number of shares initially reserved for issuance under the 2015 Stock Option Plan is the sum of (a)1,311,812 shares of common stock and (b) the number of shares under the 2014 Plan that are not needed to fulfill the Company’s obligations for awards issued under the 2014 Plan as a result of forfeiture, expiration, cancellation, termination or net issuances of awards thereunder. The number of shares of common stock that may be issued under the 2015 Stock Option Plan is also subject to increase on the first day of each fiscal year by up to 4% of the Company’s issued and outstanding shares of common stock immediately preceding December 31.

2025 Stock Option Plan

On March 18, 2025, the Company’s board of directors adopted, and on June 3, 2025, the stockholders approved, the 2025 Stock Incentive Plan (the “2025 Stock Option Plan”). Under the 2025 Stock Option Plan, the Company may issue awards for up to a number of shares of common stock equal to the sum of: (i)3,631,952 shares of common stock; and (ii) such additional number of shares of common stock (up to 14,190,976 shares) as is equal to the sum of (x) the number of shares of common stock reserved for issuance under the 2015 Stock Option Plan that remained available for grant thereunder immediately prior to the date that the 2025 Stock Option Plan was approved by the Company’s stockholders and (y) the number of shares of common stock subject to awards granted under the 2015 Stock Option Plan that were outstanding as of the date that the 2025 Stock Option Plan was approved by the Company’s stockholders and which awards expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right (subject, however, in the case of incentive stock options, to any limitations under the Internal Revenue Code of 1986, as amended, and any regulations thereunder).

The Company intends to utilize the 2025 Stock Option Plan to grant equity awards to the Company’s employees, non-employee directors, consultants, and advisors in order to recruit, incentivize, retain and reward those who are critical to the Company’s success. No new awards will be granted under the 2015 Stock Option Plan.

During the year ended December 31, 2025, the Company granted options to purchase 2,302,270 shares of common stock to employees and directors under the 2025 Stock Option Plan. Additionally, the Company granted 1,854,011 restricted stock units to employees under the 2025 Stock Option Plan.

As of December 31, 2025, there were 7,115,477 shares available for future issuance under the 2025 Stock Option Plan.

2015 Employee Stock Purchase Plan

In October 2015, the Company’s board of directors and stockholders approved the 2015 Employee Stock Purchase Plan (the “2015 ESPP”). Under the 2015 ESPP, all full-time employees of the Company are eligible to purchase common stock of the Company twice per year, at the end of eachsix-month payment period. During each payment period, eligible employees who so elect, may authorize payroll deductions in an amount of 1% to 10% (whole percentages only) of the employee’s base pay for each payroll period. At the end of each payment period, the accumulated deductions are used to purchase shares of common stock from the Company at a discount. A total of 262,362 shares of common stock were initially authorized for issuance under this plan.

On March 18, 2025, the Company’s board of directors adopted, and on June 3, 2025, the stockholders approved, the Amended and Restated 2015 Employee Stock Purchase Plan (together with the 2015 ESPP, the “ESPP”) to (i) eliminate the evergreen provision in the 2015 ESPP and (ii) expand the class of eligible employees by eliminating the requirement that participants must have completed six months of employment.

The Company issued 201,404 and 148,069 shares of common stock under the ESPP in the years ended December 31, 2025 and 2024. As of December 31, 2025, there were 1,809,493 shares available for future purchase under the ESPP.

Inducement Awards

During the years ended December 31, 2024 and 2023, the Company issued non-statutory stock options to purchase an aggregate of 486,000 and 573,000 shares of the Company’s common stock and restricted stock unit awards for an aggregate of 223,000 and 318,500 shares of the Company’s common stock, respectively, in each case outside of the Company’s 2015 Stock Option Plan and its 2025 Stock Option Plan as an inducement material to certain individuals’ acceptance of an offer of employment with the Company in accordance with Nasdaq Listing Rule 5635(c)(4). The Company did not issue any non-statutory stock options or restricted stock unit awards outside the Company’s 2015 Stock Option Plan and its 2025 Stock Option Plan during the year ended December 31, 2025. The stock options will vest over afour-year period, with 25% of the shares underlying the option award vesting on the first anniversary of the award and the remaining 75% of the shares underlying the award vesting monthly thereafter over the subsequent 36-month period. The restricted stock units vest over athree-year period, with 33% of the restricted stock units vesting on the first anniversary of the award,33% of the restricted stock units vesting on the second anniversary, and the remaining restricted stock units vesting on the third anniversary.

Stock-based Compensation Expense

Total compensation cost recognized for all stock-based compensation awards in the statements of operations and comprehensive (loss) income is as follows:

Restricted Stock Unitsand Performance Restricted Stock Units

A summaryof the status of and changes in restricted stock unit, or RSU, and performance-based restricted stock unit, or PRSU, activity under the Company’s equity award plans for the year ended December 31, 2025, was as follows:

Stock-based compensation for restricted stock units is based on the fair value of the Company’s common stock on the date of grant and is recognized over the vesting period. The restricted stock units granted during the year will vest in equal amounts, annually, over three years.

As of December 31, 2025, the Company had unrecognized stock-based compensation expense related to its unvested restricted stock units (excluding PRSUs) of $5.8 million, which is expected to be recognized over the remaining weighted average vesting period of 1.7 years.

During the year ended December 31, 2025, in connection with the Company’s annual compensation cycle, the Company also granted PRSUs to members of the Company’s senior leadership team to more closely align with long-term performance incentives. The awards vest as to a certain number of PRSUs upon the achievement of specified clinical performance milestones over multiple years. Stock-based compensation for PRSUs is based on the fair value of the Company’s common stock on the date of grant and will be recognized at the time the achievement of the specified performance milestones becomes probable. The Company didnot recognize any stock-based compensation expense in connection with the PRSUs during the year ended December 31, 2025.

As of December 31, 2025, the Company had unrecognized stock-based compensation expense related to its unvested PRSUs of $2.6 million. The Company will recognize a cumulative catch-up adjustment in the period in which the specified performance condition is considered probable.

Stock Options

A summary of the status of, and changes in, stock options was as follows:

Using the Black-Scholes option pricing model, the weighted average fair value of options granted during the years ended December 31, 2025, 2024, and 2023, was $2.82, $5.45, and $6.12, respectively.

The fair value of each option was estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:

As of December 31, 2025, the Company had unrecognized stock-based compensation expense related to its unvested stock options of $11.9 million which is expected to be recognized over the remaining weighted average vesting period of 2.3 years.

**12.**Underwritten public offering

In January 2024, the Company entered into an underwriting agreement relating to an underwritten public offering of 7,777,778 shares of the Company’s common stock, par value $0.001 per share, and, in lieu of common stock to certain investors, pre-funded warrants (the “Pre-Funded Warrants”) to purchase up to 3,333,333 shares of common stock. The underwriters agreed to purchase the Company’s stock at a price of $8.46 and the Pre-Funded Warrants at a price of $8.459 per share underlying each Pre-Funded Warrant. The Company issued 7,777,778 shares of common stock and 3,333,333 Pre-Funded Warrants for net proceeds of approximately $93.5 million after deducting underwriting discounts and commissions and offering expenses pursuant to the underwritten public offering.

During the year ended December 31, 2025, all of the Pre-Funded Warrants were exercised on a cashless basis, resulting in the issuance of 3,332,544 net shares.

13. 401(k) Savings plan

The Company has a defined-contribution savings plan under Section 401(k) of the Internal Revenue Code (the “401(k) Plan”). The 401(k) Plan covers all employees who meet defined minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pretax basis. The Company expensed approximately $1.4 million, $1.4 million, and $1.1 million related to employer contributions made during the years ended December 31, 2025, 2024, and 2023, respectively.

14. Income taxes

The provision for incomes taxes is as follows:

A reconciliation of the expected income tax provision computed using the federal statutory income tax rate at the Company’s effective tax rate is as follows:

(1) State taxes in Massachusetts comprise the majority of the tax effect in this category.

The Company has historically incurred net operating losses (“NOLs”). As of December 31, 2025, the Company had federal and state net operating loss carryforwards of $249.4 million and $236.4 million, respectively. The year-over-year increase in NOLs is primarily driven by provisions of the “One Big Beautiful Bill Act” which the Company availed itself of as discussed further below. The state NOLs will expire beginning in 2041 while the federal NOLs do not expire. As of December 31, 2025, the Company had federal and state research and development tax credit carryforwards of $29.2 million and $18.0 million, respectively, which expire beginning in 2030. As of December 31, 2025, the Company has $0.2 million of state investment credits, which expire beginning in 2026.

The significant components of the Company’s deferred tax assets and (liabilities) are as follows:

Management has evaluated the positive and negative evidence bearing upon the realizability of the Company’s deferred tax assets, which principally comprise NOL carryforwards, tax credit carryforwards, and capitalized research expenses. Management has determined that it is more likely than not that the Company will not recognize the benefits of its federal and state deferred tax assets, and as a result, a valuation allowance of $145.4 million and $105.9 million has been established at December 31, 2025 and 2024, respectively. The valuation allowance increased by $39.6 million for the year ended December 31, 2025. The primary reason for the difference between the income tax provision recorded by the Company and the amount of income tax provision at statutory income tax rates was the change in the valuation allowance.

As of December 31, 2025 and 2024, the Company hadno unrecognized tax benefits.

Cash paid for income taxes, net of refunds consists of the following:

Sections 382 and 383 of the U.S. Internal Revenue Code (“IRC”) impose substantial restrictions on the utilization of net operating losses and other tax attributes in the event of a cumulative “ownership change”. In general, a company would undergo an ownership change if its “5-percent shareholders” (determined under Section 382) increased their collective ownership of the company’s stock by more than 50% over a rolling three-year period. Accordingly, if the Company generates taxable income in the future, changes in stock ownership, including equity offerings and share repurchase programs, as well as other changes that may be outside its control, could potentially result in material limitations on the Company’s ability to use its net operating loss and research tax credit carryforwards. Similar rules may apply under state tax laws. The Company has completed an analysis of IRC Section 382 through December 31, 2023, and the amounts reflected in the tax footnote are net of any limitations on the net operating losses and credits as a result

of this analysis. The Company may have experienced ownership changes in the past, and it may experience ownership changes in the future, some of which are outside of its control. This could limit the amount of net operating losses and research tax credits that the Company can utilize annually to offset future taxable income or tax liabilities. Subsequent statutory or regulatory changes in respect to the utilization of net operating losses and research tax credits for federal or state purposes, such as suspensions or limitations on the use of net operating losses and research tax credits carried forward, or other unforeseen reasons, may result in the Company’s existing net operating losses and research tax credits expiring or otherwise being unavailable to offset future income tax liabilities.

Interest and penalty charges, if any, related to unrecognized tax benefits would be classified as income tax expense in the accompanying statements of operations. As of December 31, 2025, and 2024, the Company hasno accrued interest related to uncertain tax positions. Since the Company is in a loss carryforward position, it is generally subject to examination by the U.S. federal, state, and local income tax authorities for all tax years in which a loss carryforward is available.

On July 4, 2025, President Donald Trump signed the “One Big Beautiful Bill Act” into law, which is considered the enactment date under U.S. GAAP. Key corporate tax provisions include the restoration of 100% bonus depreciation, immediate expensing for domestic research and experimental expenditures, changes to Section 163(j) interest limitations, updates to GILTI and FDII rules, amendments to energy credits, and expanded Section 162(m) aggregation requirements. In accordance with ASC 740, the Company recognized the effects of the new tax law in the period that includes the enactment date.

15. Related-party transactions

During the years ended December 31, 2025, 2024, and 2023, the Company received scientific advisory services from one of its prior executives, Dinah Sah, Ph.D., the Company’s former Chief Scientific Officer. The total amount of fees paid to Dr. Sah for services provided during the years ended December 31, 2025, 2024, and 2023, was $0.4 million, $0.7 million, and $0.7 million, respectively.

Under both the 2019 Neurocrine Collaboration Agreement and the 2023 Neurocrine Collaboration Agreement, the Company and Neurocrine have agreed to conduct research, development and commercialization activities for certain of the Company’s AAV gene therapy products (Note 9). Amounts due from Neurocrine are reflected as related party collaboration receivable. As of December 31, 2025, the Company recorded approximately $0.2 million in related party collaboration receivable relative to the 2019 Neurocrine Collaboration Agreement and the 2023 Neurocrine Collaboration Agreement. As of December 31, 2024, the Company recorded approximately $0.7 million in related party collaboration receivable relative to the 2019 Neurocrine Collaboration Agreement and the 2023 Neurocrine Collaboration Agreement.

16. Segment Information

The Company’s CODM, the Company’s Chief Executive Officer, views the Company’s operations and manages its business as a single operating segment, which is the business of developing and commercializing genetic medicine. The Company therefore hasone reportable segment.

The CODM reviews the segment's profit or loss based on net (loss) income reported on the consolidated statement of operations and comprehensive (loss) income and considers forecast-to-actual variances monthly for expenses that are deemed significant in making resource allocation decisions and assessing performance. Further, the CODM reviews the segment's assets based on total assets reported on the consolidated balance sheets. All long-lived assets are held in the United States.

The CODM views specific categories within research and development expenses and general and administrative expenses in totality as significant. Further, the CODM reviews the external research and development expenses of specific programs as significant given the impact on achieving the Company’s corporate goals. The following table reconciles reported collaboration revenue to net (loss) income under the significant expense principle for the years ended December 31, 2025, 2024, and 2023:

(1)External research and development is allocated to the Company’s programs and platforms, and includes laboratory supplies, and non-employee consultant and contractor costs.

(2)Partnered programs include programs in which the Company is collaborating with partners to develop AAV gene therapy products and product candidates under the Company’s 2019 and 2023 Neurocrine Collaboration Agreements, and the 2023 Novartis Collaboration Agreement.

EXHIBIT INDEX

Management contract or compensatory plan or arrangement filed in response to Item 15(a)(3) of the Instructions to the Annual Report on Form 10-K.

† Confidential treatment has been granted as to certain portions, which portions have been omitted and separately filed with the Securities and Exchange Commission.

• Portions of this exhibit have been omitted pursuant to Item 601(b)(10)(iv) of Regulation S-K.

• The certification furnished in Exhibit 32.1 hereto is deemed to be furnished with this Annual Report on Form 10-K and will not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, except to the extent that the Registrant specifically incorporates it by reference.