Annual Report for Fiscal Year Ending December 31, 2025 (Form 10-K)

Management's Discussion and Analysis of Financial Condition and Results of Operations.

You should read the following discussion and analysis of our financial condition and results of operations together with our financial statements and the related notes included elsewhere in this Annual Report on Form 10-K (this "report"). This discussion and analysis and other parts of this report contain forward-looking statements based upon current beliefs, plans and expectations related to future events and our future financial performance that involve risks, uncertainties and assumptions, such as statements regarding our intentions, plans, objectives, expectations, forecasts and projections. Our actual results and the timing of selected events could differ materially from those anticipated in these forward-looking statements as a result of several factors, including those set forth under the section titled "Risk Factors" and elsewhere in this report.

Overview

We are a leading late-stage biotechnology company advancing durable and disease-targeted therapeutics with potential to transform treatment paradigms and provide unprecedented benefits to patients. Our primary focus is advancing 4D-150 for wet age-related macular degeneration ("wet AMD") and diabetic macular edema ("DME") through late-stage studies and potential commercialization and advancing our other pipeline programs, 4D-175 for geographic atrophy, 4D-710 for CF lung disease, and 4D-725 for A1AT lung disease primarily through external funding including strategic partnerships. We believe we are well positioned to discover, develop, manufacture and if approved, commercialize targeted genetic medicines with the potential to transform the lives of patients suffering from debilitating diseases.

Our lead product candidate 4D-150 utilizes our proprietary R100 vector and a transgene encoding anti-VEGF biologics: aflibercept and an RNA interference (RNAi) approach targeting VEGF-C. The goal for our development and potential commercialization of 4D-150 is to transform the standard of care for large market retinal vascular diseases with a safe, in-office, and durable lifelong backbone therapy substantially reducing treatment burden and improving long-term vision outcomes. 4D-150 is initially being developed for the treatment of wet AMD and DME.

In March 2025, we initiated 4FRONT-1, our first Phase 3 trial of 4D-150 in wet AMD. Subsequently in February 2026, we announced enrollment completion within an approximately 11-month period, ahead of initial projections, with the clinical trial overenrolled and expected to exceed 500 patients randomized, reflecting strong interest from investigators and patients. We anticipate topline data with the 52-week primary endpoint in the first half of 2027.

Additionally, 4FRONT-2, our second Phase 3 trial of 4D-150 in wet AMD, was initiated in June 2025. 4FRONT-2 is a global clinical trial and is enrolling both treatment-naïve and recently diagnosed, treatment-experienced patients. We expect 52-week topline data for 4FRONT-2 in the second half of 2027.

In November 2025, we announced positive long-term interim results from the ongoing 4D-150 PRISM Phase 1/2 clinical trial in wet AMD. 4D-150 demonstrated consistent and durable benefit across all three patient cohorts as evidenced by maintenance of visual acuity, control of retinal anatomy and reduction of treatment burden at all time points with 1.5 to 2 years of follow-up. In addition, a consistent dose response was observed between 3E10 vg/eye, the selected Phase 3 dose, and the lower dose of 1E10 vg/eye. The Phase 3 dose achieved clinically meaningful reductions in treatment burden. No new cases of intraocular inflammation were reported during this follow-up period with up to approximately 3.5 years of follow-up.

In July 2025, we presented positive 60-week results from the 4D-150 SPECTRA clinical trial in DME where 4D-150 continued to be well tolerated with no intraocular inflammation observed at any timepoint or dose level. In addition, 4D-150 demonstrated durable and dose-dependent clinical activity with sustained gains in visual acuity and anatomic control between 3E10 vg/eye, the selected Phase 3 dose, and lower doses. The Phase 3 dose achieved clinically meaningful 78% reduction in treatment burden vs. projected on-label aflibercept 2mg Q8W. The FDA and EMA are aligned on a proposed single Phase 3 clinical trial being acceptable for possible future licensure for 4D-150 in DME.

In October 2025, we entered into a Collaboration and License Agreement with Otsuka Pharmaceutical Co., Ltd. (the "Otsuka Collaboration and License Agreement"), pursuant to which we granted Otsuka exclusive rights to develop and commercialize 4D-150 for retinal vascular diseases, including wet AMD and DME, in Japan, China, Australia, and other APAC markets. Otsuka has agreed to lead all regulatory and commercialization activities in its licensed territories. We have agreed to continue to lead all Phase 3 clinical activity globally, including within the APAC region. Otsuka made an upfront cash payment of $85 million and agreed to provide certain cost sharing for global development activities. In addition, we are eligible for up to $335.5 million in potential regulatory and commercial milestone payments and tiered double-digit royalties depending on net sales in Otsuka's licensed territories. We retain full development and commercialization rights for 4D-150 outside the APAC region, including the United States, Latin America, and Europe.

Our other pipeline programs include 4D-710, which we believe is the first known genetic medicine to demonstrate successful delivery and durable expression of the cystic fibrosis transmembrane conductance regulator ("CFTR") transgene in the lungs of people with cystic fibrosis ("CF") and is currently in Phase 2 development. We believe these results will translate into durable clinical improvements in people with CF, including improved lung function and quality of life. In October 2025, we announced a funding agreement with the Cystic Fibrosis Foundation ("CFF") to provide up to $11 million in additional funding, including $7.5 million in an initial tranche, which was completed in October 2025. The proceeds of this funding agreement enabled the start of the Phase 2 stage of the AEROW clinical trial, redosing, and Phase 3 readiness activities. 

We have funded our operations primarily through the sale and issuance of equity securities and to a lesser extent from cash received pursuant to our collaboration and license agreements.

Our net losses were $140.1 million and $160.9 million for the years ended December 31, 2025 and 2024, respectively. As of December 31, 2025, we had an accumulated deficit of $716.3 million. We do not expect positive cash flows from operations in the foreseeable future. Our net losses may fluctuate significantly from quarter-to-quarter and year-to-year, depending on the timing of our clinical trials and our expenditures on other research and development activities.

We do not have any products approved for sale and have not generated any revenue from product sales since our inception. Our ability to generate product revenue will depend on the successful development, regulatory approval and eventual commercialization of one or more of our product candidates, if approved.

We will require substantial additional funding to support our continuing operations and further the development of our product candidates. Until such time as we can generate significant revenue from product sales, if ever, we expect to finance our operations through the sale of equity, debt financings, or other capital sources, which could include income from collaborations, strategic partnerships, or other strategic arrangements, for the foreseeable future. Adequate funding may not be available when needed or on terms acceptable to us, or at all. Our ability to raise additional funds may be adversely impacted by potential worsening global economic conditions and the recent disruptions to, and volatility in, the credit and financial markets in the United States and worldwide resulting from conflicts in the Middle East, the lingering impact of the COVID-19 pandemic, the war in Ukraine, rising interest rates, tariffs, inflation, government shutdowns and otherwise. If we fail to obtain necessary capital when needed on acceptable terms, or at all, it could force us to delay, limit, reduce or terminate our product development programs, commercialization efforts or other operations. Insufficient liquidity may also require us to relinquish rights to product candidates at an earlier stage of development or on less favorable terms than we would otherwise choose. We cannot assure you that we will ever be profitable or generate positive cash flow from operating activities.

Restructuring and Other Charges

On July 2, 2025, we announced a workforce reduction of approximately 25% of current and planned roles, primarily in the areas supporting early-stage research and development and support functions following a strategic pipeline prioritization to focus on the development of 4D-150 and 4D-710. In connection with the workforce reduction, the Company recorded total expense of $3.2 million including severance, benefits and related termination costs during the year ended December 31, 2025. There are no future payments in connection with the workforce reduction.

Components of Results of Operations

Revenue

Our revenue to date has been generated through payments from our collaboration and license agreements, primarily from upfront and milestone payments and expense reimbursement. We have not generated any revenue from the sale of approved products and do not expect to do so for the foreseeable future.

In October 2025, we entered into the Otsuka Collaboration and License Agreement where we granted Otsuka exclusive rights to develop and commercialize 4D-150 for retinal vascular diseases, including wet AMD and DME, in Japan, China, Australia, and other Asia-Pacific markets. Otsuka made an upfront cash payment of $85 million which we recognized as revenue during the fourth quarter of 2025, and agreed to provide certaincost sharing for global development activities.

In August 2019, we amended our agreement with uniQure (the "Amended uniQure Agreement") and entered into a separate new collaboration and license agreement with uniQure (the "Second uniQure Agreement"). Neither party was required to pay monetary consideration in connection with the amendment or new agreement. We determined the incremental transaction price of the amendment and new agreement to be $5.1 million and recorded the amount as deferred revenue in August 2019. We began recognizing revenue related to uniQure in 2020 and recognized the remaining revenue under the agreement during the third quarter of 2023. We recognized immaterial revenue during the year ended December 31, 2023 related to this agreement. See Note 6, Research and Collaboration Agreements, to our financial statements included elsewhere in this report for further discussion regarding the accounting treatment of this agreement. The Amended uniQure Agreement and the Second uniQure Agreement were terminated by mutual agreement in November 2025. We did not incur any charges related to the termination of the uniQure Agreement.

Future collaboration and license revenue is highly dependent on the successful development and commercialization of products by our collaboration partners, which is uncertain, and revenue may fluctuate significantly from period to period. Additionally, we may never receive the consideration from our license agreements that is contemplated for option fees, development and sales-based milestone payments or royalties on sales of licensed products, given the contingent nature of these payments.

Operating Expenses

Research and Development

Our research and development expenses primarily consist of costs incurred for the discovery and preclinical and clinical development of our product candidates. These expenses include salaries and personnel-related costs, including stock-based compensation of our clinical, medical, chemistry, manufacturing and controls and scientific personnel performing research and development activities; laboratory supplies; research materials; fees paid to CROs to execute preclinical studies and clinical trials; fees paid to CDMOs to manufacture materials for preclinical studies and clinical trials; fees related to obtaining technology licenses; consulting costs; costs related to seeking regulatory approval of our product

candidates; and allocated facility-related costs, information technology costs, depreciation expense, and other overhead.

We expense all research and development costs in the periods in which they are incurred. We have entered into various agreements with CROs and CDMOs. Costs of certain activities are recognized based on an evaluation of the progress to completion of specific tasks. Payments made prior to the receipt of goods or services that will be used or rendered for future research and development activities are deferred and capitalized as prepaid expenses and other current assets on our balance sheet. The capitalized amounts are recognized as expense as the goods are delivered or the related services are performed.

We do not allocate our costs by product candidate, as a significant amount of research and development expenses includes internal costs, such as salary and other personnel-related expenses, laboratory supplies and allocated overhead, and external costs, such as fees paid to third parties to conduct research and development activities on our behalf, none of which are tracked by product candidate. In particular, with respect to internal costs, several of our departments support multiple product candidate research and development programs and, therefore, the costs cannot be allocated to a particular product candidate or development program.

At this time, we cannot reasonably estimate or know the nature, timing or estimated costs of the efforts that will be necessary to complete the development of, and obtain regulatory approval for, any of our product candidates. However, we expect our overall research and development expenses to increase in the near term primarily for 4D-150 Phase 3 trials in wet AMD and DME. The process of conducting the necessary clinical development to obtain regulatory approval is costly and time-consuming, and the successful development of our product candidates is highly uncertain. See the section titled "Risk Factors" for additional risks regarding regulatory development and approval.

General and Administrative

Our general and administrative expenses consist primarily of personnel-related expenses, including salaries, employee benefit costs and stock-based compensation expense for our personnel in executive, finance and accounting, legal, human resources, business development, and other administrative functions. General and administrative expenses also include professional fees for legal, patent, consulting, accounting and tax services, allocated overhead, including rent, equipment, depreciation, information technology costs and utilities, and other general operating expenses not otherwise classified as research and development expenses.

Other Income, Net

Our other income, net primarily consists of interest income earned on our cash equivalents and marketable securities and adjustments for the change in the fair value of our derivative liability which must be remeasured at each reporting date.

Results of Operations

Comparison of the Years Ended December 31, 2025 and 2024

The following table summarizes our results of operations for the periods indicated (dollars in thousands):

* not meaningful

Revenue

Revenue for the year ended December 31, 2025 increased by $85.2 million from the year ended December 31, 2024. The increase in revenue was primarily due to the upfront fees received from the Otsuka Collaboration and License Agreement in October 2025.

Research and Development Expenses

The following table provides a breakout of research and development expenses for the periods indicated (dollars in thousands):

Research and development expenses for the year ended December 31, 2025 increased by $54.4 million, or 38%, from the year ended December 31, 2024. The increase was due to the following:

General and Administrative Expenses

General and administrative expenses for the year ended December 31, 2025 increased by $2.5 million, or 5%, from the year ended December 31, 2024. The increase was primarily due to an increase in legal and consulting services.

Other Income, Net

Other income, net, decreased by $7.5 million, or 28%, from the year ended December 31, 2024 to the year ended December 31, 2025. The decrease was due to a reduction in invested balances from transfers out of investment accounts to fund operating expenses and lower market yields on our cash equivalents and marketable securities.

Liquidity and Capital Resources

Sources of Liquidity

As of December 31, 2025, we had cash, cash equivalents and marketable securities of $514.0 million. We have funded our operations primarily through the sale and issuance of our equity securities, including Follow-on Offerings and our "at-the-market" offering program, and to a lesser extent from cash received pursuant to our collaboration and license agreements. Our recent sources of liquidity include the following transactions:

Follow-on Offerings

In November 2025, we completed an underwritten offering (the "2025 Offering") in which 8,385,809 shares of our common stock were sold at an offering price of $10.51 per share, as well as pre-funded warrants to purchase 1,128,949 shares of our common stock at an offering price of $10.5099 per underlying share. The net proceeds from the 2025 Offering were approximately $93.3 million, after deducting the underwriting discounts and commissions and other offering expenses.

In February 2024, we completed the 2024 Offering in which 6,586,015 shares of our common stock were sold at an offering price of $29.50 per share, as well as pre-funded warrants to purchase 3,583,476 shares of our common stock at an offering price of $29.4999 per underlying share. The net proceeds from the 2024 Offering were $281.2 million, after deducting underwriting discounts and commissions and other offering expenses. We also granted the underwriters the option to purchase up to 1,525,423 additional shares of common stock in connection with the offering. In March 2024, the underwriters exercised their option and purchased 1,259,299 additional shares of common stock resulting in net proceeds of $34.9 million, after deducting underwriting discounts and commissions.

In May 2023, we completed the 2023 Offering in which 8,625,000 shares of our common stock were sold at an offering price of $16.00 per share. The net proceeds from the 2023 Offering were $129.2 million after deducting underwriting discounts and commissions and offering expenses. 

At-the-Market Offering Program

In June 2024, we entered into a Sales Agreement (the "Leerink Sales Agreement") with Leerink Partners LLC ("Leerink") as sales agent to sell shares of our common stock, from time to time, with aggregate gross sales proceeds of up to $250.0 million pursuant to a Registration Statement on Form S-3 that we filed with the SEC in February 2024 as an "at-the-market" offering under the Securities Act. For the year ended December 31, 2025, 1,175,000 shares of the Company's common stock were sold pursuant to the Leerink Sales Agreement for net proceeds to the Company of $9.6 million, after deducting issuance costs.

In March 2022, we also entered into an Open Market Sales Agreement (the "Sales Agreement") with Jefferies LLC as sales agent to sell shares of our common stock, from time to time, with aggregate gross sales proceeds of up to $100.0 million pursuant to the S-3 Registration Statement as an "at-the-market" offering under the Securities Act (the "2022 ATM Offering Program"). On May 31, 2024, we terminated the Sales Agreement and the 2022 ATM Offering Program pursuant to the terms of the Sales Agreement. At termination, 1,684,550 shares of our common stock had been sold pursuant to the Sales Agreement for net proceeds to us of $34.4 million, after deducting issuance costs.

Collaboration and License Agreements

In October 2025, we entered into a Collaboration and License Agreement with Otsuka where we granted Otsuka exclusive rights to develop and commercialize 4D-150 for retinal vascular diseases, including wet AMD and DME, in Japan, China, Australia, and other Asia-Pacific markets. Otsuka made an upfront cash payment of $85 million and agreed to provide certain cost sharing for global development activities.

In July 2023, we entered into the License Agreement with AGT where we provided our 4D vector technology to AGT to deliver AGT's genetic payloads for the treatment of rare monogenic diseases. As partial consideration for the rights and licenses granted to AGT under the License Agreement, we received an upfront payment of $20.0 million.

Future Funding Requirements

We have experienced recurring net losses and had an accumulated deficit of $716.3 million at December 31, 2025. Our transition to profitability is dependent upon the successful development, approval and commercialization of our product candidates and those of our collaboration partners and achieving a level of revenue adequate to support our cost structure. We expect to continue to incur losses for the foreseeable future.

We expect that our overall research and development and general and administrative expenses will increase. As a result, we will need significant additional capital to fund our operations, which we may obtain through one or more equity offerings, debt financings or other third-party funding, the Otsuka Collaboration and License Agreement, and additional potential strategic alliances and licensing or collaboration arrangements.

Because of the numerous risks and uncertainties associated with the development and commercialization of gene therapy product candidates, we are unable to estimate the amount of increased capital we will need to raise to support our operations and the outlays and operating expenditures necessary to complete the development of our product candidates and build additional manufacturing capacity, and we may use our available capital resources sooner than we currently expect.

Our future capital requirements will depend on many factors, including:

We believe that our existing cash, cash equivalents and marketable securities will allow us to fund our planned operations for at least one year from the date of the issuance of the financial statements included in this report.

We have based our estimates as to how long we expect we will be able to fund our operations on assumptions that may prove to be wrong, and we could use our available capital resources sooner than we currently expect, in which case we would be required to obtain additional financing sooner than currently projected, which may not be available to us on acceptable terms, or at all. Our failure to raise capital as and when needed would have a negative impact on our financial condition and our ability to pursue our business strategy. See the section titled "Risk Factors" for additional risks associated with our substantial capital requirements.

We have limited committed external sources of funds. Accordingly, we will be required to obtain further funding through public or private equity offerings, debt financings, collaborations and licensing arrangements or other sources to complete the clinical development for the product candidates for treatment of wet AMD, DME, geographic atrophy, cystic fibrosis lung disease, alpha-1 antitrypsin deficiency lung disease or any other indication we may pursue. If we raise additional funds by issuing equity securities, our stockholders may experience dilution. Any future debt financing into which we enter would result in fixed payment obligations and may involve agreements that include grants of security interests on our assets and restrictive covenants that limit our ability to take specific actions, such as incurring additional debt, making capital expenditures, granting liens over our assets, redeeming stock or declaring dividends, that could adversely impact our ability to conduct our business. Any debt financing or additional equity that we raise may contain terms that could adversely affect our common stockholders. Further, additional funds may not be available when we need them, on terms that are acceptable to us, or at all. Our ability to raise additional capital may be adversely impacted by potential worsening global economic conditions and the recent disruptions to and volatility in the credit and financial markets in the United States and worldwide resulting from the war in Ukraine, conflicts in the Middle East, any expansion of these conflicts, rising interest rates and inflation, natural disasters and pandemics.

If we are unable to obtain additional funding, we expect to delay, reduce or eliminate some or all of our research and development programs, product portfolio expansion or investment in manufacturing

capabilities, which could adversely affect our business. If we raise additional funds through collaborations or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to future revenue streams or product candidates or grant licenses on terms that may not be favorable to us.

Summary Statement of Cash Flows

The following is a summary of cash flows for the periods indicated below (in thousands):

Net Cash Used in Operating Activities

Net cash used in operating activities was $109.1 million for the year ended December 31, 2025. This was primarily due to the net loss of $140.1 million partially offset by a change of $24.8 million in noncash charges and by a net change of $6.2 million in our operating assets and liabilities. The noncash charges primarily consisted of stock-based compensation expense of $22.0 million, depreciation and amortization of $4.7 million and amortization of operating lease right-of-use assets of $2.9 million, partially offset by accretion of discount on marketable securities of $4.7 million and $0.1 million in change in fair value of derivative liability. The change in operating assets and liabilities was primarily due to an $8.1 million increase in accrued and other liabilities, a $6.8 million increase in accounts payable, offset by a $3.2 million decrease in operating lease liabilities, a $0.2 decrease in deferred revenue, a $0.4 million increase in prepaid expenses and other current assets and a $4.9 million increase in other assets.

Net cash used in operating activities was $134.6 million for the year ended December 31, 2024. This was primarily due to the net loss of $160.9 million partially offset by a change of $25.7 million in noncash charges and by a net change of $0.5 million in our operating assets and liabilities. The noncash charges primarily consisted of stock-based compensation expense of $26.1 million, depreciation and amortization of $4.7 million and amortization of operating lease right-of-use assets of $2.1 million, partially offset by accretion of discount on marketable securities of $7.2 million. The change in operating assets and liabilities was primarily due to a $6.5 million increase in accrued and other liabilities, a $0.9 million increase in accounts payable and $0.1 million increase in deferred revenue, offset by a $1.7 million decrease in operating lease liabilities, a $1.7 million increase in prepaid expenses and other current assets and a $3.6 million increase in other assets.

Net Cash Used in Investing Activities

Net cash used in investing activities was $93.0 million for the year ended December 31, 2025. This was due to purchases of marketable securities of $442.8 million and purchases of property and equipment of $0.5 million, offset by maturities of marketable securities of $350.4 million.

Net cash used in investing activities was $302.4 million for the year ended December 31, 2024. This was due to purchases of marketable securities of $467.6 million and purchases of property and equipment of $3.8 million, offset by maturities of marketable securities of $169.0 million.

Net Cash Provided by Financing Activities

Net cash provided by financing activities was $113.0 million for the year ended December 31, 2025. This was due to proceeds from the issuance of common stock upon underwritten offering, net of issuance costs, of $93.5 million, proceeds from the issuance of common stock from the ATM Offering Program of $9.7 million, proceeds from the issuance of common stock under a stock purchase agreement of $7.5 million, proceeds from the issuance of common stock from purchases from the Company's 2020 Employee Stock Purchase Plan ("ESPP") of $1.3 million, and proceeds from the issuance of common stock from the exercise of stock options and warrants of $1.0 million.

Net cash provided by financing activities was $337.3 million for the year ended December 31, 2024. This was due to proceeds from the issuance of common stock upon public offering, net of issuance costs, of $316.1 million, proceeds from the issuance of common stock from the 2022 ATM Offering Program of $15.3 million, proceeds from the issuance of common stock from the exercise of stock options and warrants of $4.6 million and proceeds from the issuance of common stock from purchases from the ESPP of $1.3 million.

Contractual Obligations, Commitments and Contingencies

Our commitments include obligations under vendor contracts to provide research services and other purchase commitments with our vendors. In the normal course of business, we enter into services agreements with contract research organizations, contract manufacturing organizations and other third parties. Generally, these agreements provide for termination upon notice, with specified amounts due upon termination based on the timing of termination and the terms of the agreement. The actual amounts and timing of payments under these agreements are uncertain and contingent upon the initiation and completion of the services to be provided. These amounts are not fixed and determinable.

As of December 31, 2025, our principal commitments consisted of obligations under our operating lease for our headquarters. Please see Note 8, Commitments and Contingencies, to our financial statements included elsewhere in this report.

Critical Accounting Policies and Significant Judgments and Estimates

Our financial statements have been prepared in accordance with generally accepted accounting principles in the United States. The preparation of our financial statements requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of our financial statements, as well as the reported revenue and expenses during the reported periods. We evaluate these estimates and assumptions on an ongoing basis. We base our estimates on historical experience and on various other factors that we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Actual results may differ from these estimates under different assumptions or conditions.

Our significant accounting policies are described in Note 2, Summary of Significant Accounting Policies, to our financial statements included elsewhere in this report. We believe the following accounting policies are critical to the process of making significant judgments and estimates in the preparation of our financial statements and understanding and evaluating our reported financial results.

Revenue Recognition

We determine revenue recognition for arrangements within the scope of Accounting Standards Update 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASC 606") by performing the following five steps: (i) assessment whether a contract with a customer exists; (ii) determination of whether the promised goods or services are performance obligations; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance

obligations based on estimated standalone selling prices; and (v) recognition of revenue when (or as) we satisfy each performance obligation.

Our revenue is primarily derived through its license, research, development and commercialization agreements. The terms of these types of agreements may include (i) licenses to our technology, (ii) research and development services, and (iii) supplies of clinical and commercial materials. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer, and is the unit of account in ASC 606. Significant judgment is required to determine whether the individual promised goods or services are distinct. Items are considered distinct if the customer can benefit from them on their own, or together with other readily available resources, and if they are separately identifiable from other items in the contract.

Payments to us under these arrangements typically include one or more of the following: nonrefundable upfront and license fees, cost-sharing and other forms of research funding, milestone and other contingent payments to us for the achievement of defined collaboration objectives and certain preclinical, clinical, regulatory and sales-based events, as well as royalties on sales of any commercialized products.

We recognize as revenue sales-based royalties and milestone payments at the later of (i) when the related sales occur, or (ii) when the performance obligation to which the royalty has been allocated has been satisfied.

Other variable amounts, such as cost-sharing and development and regulatory milestones, are included in the transaction price to the extent it is probable a significant reversal of cumulative revenue recognized will not occur when the associated uncertainties are resolved. We use the most likely or expected value amount methods as appropriate to estimate variable consideration.

At the end of each reporting period, we re-evaluate the estimated variable consideration included in the transaction price and any related constraint, and if necessary, adjusts its estimate of the overall transaction price.

We allocate the total transaction price to each performance obligation based on the estimated standalone selling prices. Variable consideration is allocated to the specific performance obligations if it is triggered by our performance or the outcomes from such performance, and if such allocation meets the allocation objective of recognizing revenue in amounts of consideration to which we expect to be entitled in exchange for transferring its promised goods or services to the customer.

We recognize revenue when, or as, the performance obligation is satisfied. Performance obligations recognized at a point in time, such as distinct licenses our intellectual property, are recognized when control transfers, including commencement of the license term. Performance obligations recognized over time, such as research and development services, are recognized using an appropriate measure of progress, such as total cost incurred.

We record accounts receivable when our right to consideration is unconditional, i.e. if and only passage of time is required before payment is due. Amounts collected or included in accounts receivable but not yet recognized in revenue are recorded as deferred revenues. Amounts recognized in revenue but not included in accounts receivable are recorded as contract assets.

Significant management judgment is required to determine the level of effort required under an arrangement and the period over which we expect to complete our performance obligations under the arrangement. Changes in these estimates can have a material effect on revenue recognized.

Accrued Clinical Research Organization Costs

We estimate our accrued clinical research organization costs as of each balance sheet date. This process involves reviewing contracts and purchase orders with service providers, identifying services that have been performed on our behalf and estimating the level of service performed, the expected remaining period of performance and the associated expenses incurred for the service when we have not yet been invoiced or otherwise notified of actual cost. Depending on the timing of payments to the service providers and the estimated expenses incurred, we may record net prepaid or accrued clinical research organization expenses relating to these costs.

Examples of estimated accrued research and development expenses include fees paid to:

Our understanding of the status and timing of services performed relative to the actual status and timing may vary and may result in us reporting changes in estimates in any particular period. To date, there have been no material differences from our estimates to the amounts actually incurred.

Stock-Based Compensation Expense

We use a fair value-based method to account for all stock-based compensation arrangements with employees and nonemployees including stock options and stock awards. Our determination of the fair value of stock options on the date of grant utilizes the Black-Scholes option pricing model.

The fair value of the option granted is recognized on a straight-line basis over the period during which an optionee is required to provide services in exchange for the option award, known as the requisite service period, which usually is the vesting period. Prior to January 1, 2020, the stock-based compensation expense for nonemployees was subject to remeasurement until the related vesting conditions were met. Effective January 1, 2020, the measurement date for nonemployee awards is the date of grant without changes in the fair value of the award. We account for forfeitures as they occur for both employees and nonemployees.

Estimates of the fair value of equity awards as of the grant date using valuation models such as the Black-Scholes option pricing model are affected by assumptions with a number of complex variables.

Changes in the following assumptions can materially affect the estimate of fair value and ultimately how much stock-based compensation expense is recognized; and the resulting change in fair value, if any, is recognized in our statements of operations during the period the related services are rendered. These inputs are subjective and generally require significant analysis and judgment to develop:

As of December 31, 2025, the unrecognized stock-based compensation expense related to stock options and RSUs was $34.2 million and is expected to be recognized as expense over a weighted-average period of approximately 1.7 years. The intrinsic value of all outstanding stock options as of December 31, 2025 was approximately $4.6 million, of which $1.0 million related to vested stock options and $3.6 million related to unvested stock options.

Income Taxes

We account for income taxes under the asset and liability method, which requires, among other things, that deferred income taxes be provided for temporary differences between the financial statement reporting and tax basis of our assets and liabilities. In addition, deferred tax assets are recorded for the future benefit of utilizing net operating losses and research and development credit carryforwards and are measured using the enacted tax rates and laws that will be in effect when such items are expected to reverse. A valuation allowance is provided against deferred tax assets unless it is more likely than not that they will be realized.

We account for uncertain tax positions by assessing all material positions taken in any assessment or challenge by relevant taxing authorities. Assessing an uncertain tax position begins with the initial determination of the position's sustainability and is measured at the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement. Our policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest or penalties charged in relation to the unrecognized tax benefits.

NOLs and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three-year period in excess of 50% as defined under Sections 382 and 383 in the Internal Revenue Code, which could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities.

Off-Balance Sheet Arrangements

Since our inception, we have not engaged in any off-balance sheet arrangements as defined in the rules and regulations of the SEC.

Recent Accounting Pronouncements

See Note 2, Summary of Significant Accounting Policies, to our financial statements included elsewhere in this report for information.