aTYR PHARMA INC

Report of Independent Regist ered Public Accounting Firm

To the Stockholders and the Board of Directors of aTyr Pharma, Inc.

Opinion on the Financial Statements

We have audited the accompanying consolidated balance sheets of aTyr Pharma, Inc. (the Company) as of December 31, 2024 and 2023, the related consolidated statements of operations, comprehensive loss, stockholders’ equity and cash flows for each of the three years in the period ended December 31, 2024, and the related notes (collectively referred to as the “consolidated financial statements”). In our opinion, the consolidated financial statements present fairly, in all material respects, the financial position of the Company at December 31, 2024 and 2023, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2024, in conformity with U.S. generally accepted accounting principles.

Basis for Opinion

These financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on the Company’s financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. The Company is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audits we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Company’s internal control over financial reporting. Accordingly, we express no such opinion.

Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion.

Critical Audit Matter

The critical audit matter communicated below is a matter arising from the current period audit of the financial statements that was communicated or required to be communicated to the audit committee and that: (1) relates to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective or complex judgments. The communication of the critical audit matter does not alter in any way our opinion on the consolidated financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the account or disclosure to which it relates.

/s/Ernst & Young LLP

We have served as the Company’s auditor since 2008.

San Diego, California

March 13, 2025

Consolidated Balance Sheets

(in thousands, except share and per share data)

Consolidated Statements of Operations

(in thousands, except share and per share data)

Consolidated State ments of Comprehensive Loss

(in thousands)

Consolidated Statements of Stockholders’ Equity

(in thousands, except share data)

Consolidated Statements of Cash Flows

(in thousands)

Notes to Consolidated Financial Statements

1. Organization, Business and Basis of Presentation

Organization and Business

We were incorporated in the state of Delaware on September 8, 2005. We are a clinical stage biotechnology company leveraging evolutionary intelligence to translate tRNA synthetase biology into new therapies for fibrosis and inflammation. tRNA synthetases are ancient, essential proteins that have evolved novel domains that regulate diverse pathways extracellularly in humans. Our discovery platform is focused on unlocking hidden therapeutic intervention points by uncovering signaling pathways driven by our proprietary library of domains derived from all 20 tRNA synthetases.

Principles of Consolidation

Our consolidated financial statements include our accounts and our 98% majority-owned subsidiary in Hong Kong, Pangu BioPharma Limited (Pangu BioPharma). All intercompany transactions and balances are eliminated in consolidation.

Liquidity and Financial Condition

We have incurred losses and negative cash flows from operations since our inception. As of December 31, 2024, we had an accumulated deficit of $532.0 million and we expect to continue to incur net losses for the foreseeable future. As of December 31, 2024, our cash, cash equivalents, available-for-sale investments and restricted cash were $75.1 million. We currently have an “at-the-market” offering program (the Jefferies ATM Offering Program) through an Open Market Sale Agreement SM with Jefferies LLC (Jefferies). During the year ended December 31, 2024, we sold an aggregate of 20,653,450 shares of common stock at a weighted-average price of $2.02 per share for net proceeds of approximately $40.3 million under the Jefferies ATM Offering Program. Additionally, from January 1, 2025 through March 12, 2025, we sold an aggregate of 4,797,682 shares of common stock at a weighted-average price of $3.92 per share for net proceeds of approximately $18.3 million under the Jefferies ATM Offering Program.

We do not expect to generate any revenues from product sales unless and until we successfully complete development and obtain regulatory approval for one or more of our product candidates, which we expect will take a number of years at a minimum. If we obtain regulatory approval for any of our product candidates, we expect to incur significant commercialization expenses related to product sales, marketing, manufacturing and distribution. Accordingly, we will need to raise substantial additional capital to fund our operations. The amount and timing of our future funding requirements will depend on many factors, including the pace and results of our preclinical and clinical development efforts and the timing and nature of the regulatory approval process for our product candidates. We anticipate that we will seek to fund our operations through equity offerings, grant funding, collaborations, strategic partnerships and/or licensing arrangements, and when we are closer to commercialization of our product candidates potentially through debt financings. However, we may be unable to raise additional capital or enter into such arrangements when needed on favorable terms or at all. Our failure to raise capital or enter into such arrangements when needed would have a negative impact on our financial condition and ability to develop our product candidates.

We believe that our current cash, cash equivalents, available-for-sale investments and restricted cash, will be sufficient to meet our anticipated cash requirements for a period of at least one year from the date of this Annual Report.

Restricted Cash

As of December 31, 2024, restricted cash was approximately $3.0 million, which was held as a security deposit in conjunction with our corporate headquarter facility lease and financing leases as discussed further in Note 6 - Commitments and Contingencies.

Use of Estimates

Our consolidated financial statements are prepared in accordance with generally accepted accounting principles (GAAP). The preparation of our consolidated financial statements requires us to make estimates and assumptions that impact the reported amounts of assets, liabilities and expenses and the disclosure for these items in our consolidated financial statements and accompanying notes. The most significant estimates in our consolidated financial statements relate to the fair value of equity issuances and awards, and clinical trial and research and development expenses. Although these estimates are based on our knowledge of current events and actions we may undertake in the future, actual results may ultimately differ materially from these estimates and assumptions.

Segment Reporting

Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker (CODM) in making decisions regarding resource allocation and assessing performance. We view our operations and manage our business inone operating segment, which includes all activities related to the discovery and development of our product candidates. Our CODM is our Chief Executive Officer, who reviews and evaluates consolidated research and development expenses, general and administrative expenses, net loss, net cash used in operating activities and our consolidated cash and cash equivalents for purposes of making operating decisions, allocating resources and planning and forecasting future periods.

The table below summarizes the significant expense categories regularly reviewed by our CODM for the years ended December 31, 2024, 2023 and 2022.

2. Summary of Significant Accounting Policies

Cash and Cash Equivalents and Restricted Cash

Cash, cash equivalents and restricted cash consist of checking, money market and highly liquid investments that are readily convertible to cash and that have an original maturity of three months or less from date of purchase. The carrying amounts approximate fair value due to the short maturities of these instruments.

Employee Retention Credit

Under the Coronavirus Aid, Relief, and Economic Security Act of 2020 (CARES Act), we were eligible to claim the employee retention credit (ERC), which is a refundable tax credit against certain employment taxes. During the year ended December 31, 2023, we amended certain payroll tax filings and applied for a refund of $1.2 million of ERC benefits. The refund was recorded within the other receivables in our consolidated balance sheets, and as a $0.8 million reduction of research and development expenses and a $0.4 million reduction of general and administrative expenses in our consolidated statements of operations for the year ended December 31, 2023. Subsequent to the year ended December 31, 2024, in February 2025, we received a refund totaling $1.0 million of ERC benefits.

Allowance of Credit Losses

For available-for-sale securities in an unrealized loss position, we first assess whether we intend to sell, or if it is more likely than not that we will be required to sell, the security before recovery of its amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the security’s amortized cost basis is written down to fair value through earnings. For available-for-sale securities that do not meet the aforementioned criteria, we evaluate whether the decline in fair value has resulted from credit losses or other factors. In making this assessment, we consider the severity of the impairment, any changes in interest rates, market conditions, changes to the underlying credit ratings and forecasted recovery, among other factors. The credit-related portion of unrealized losses, and any subsequent improvements, are recorded in interest income through an allowance account. Any impairment that has not been recorded through an allowance for credit losses is included in other comprehensive income (loss) on the consolidated statements of operations and comprehensive loss.

We elected the practical expedient to exclude the applicable accrued interest from both the fair value and amortized costs basis of our available-for-sale securities for purposes of identifying and measuring an impairment. Accrued interest receivable on available-for-sale securities is recorded within other receivables on our consolidated balance sheets. Our accounting policy is to not measure an allowance for credit loss for accrued interest receivable and to write-off any uncollectible accrued interest receivable as a reversal of interest income in a timely manner, which we consider to be in the period in which we determine the accrued interest will not be collected by us.

Concentration of Credit Risk

Financial instruments that potentially subject us to significant concentration of credit risk consist primarily of cash, cash equivalents, restricted cash and available-for-sale investments. We have established guidelines regarding diversification of investments and their maturities, which are designed to maintain principal and maximize liquidity. We maintain deposits in federally insured financial institutions in excess of federally insured limits. We have not experienced any losses in such accounts and we believe that we are not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held.

Property and Equipment

Property and equipment are stated at cost and depreciated on a straight-line basis over the estimated useful life of the related assets (generally three toseven years). Leasehold improvements are stated at cost and amortized on a straight-line basis over the lesser of the remaining term of the related lease or the estimated useful life of the leasehold improvements. Repairs and maintenance costs are charged to expense as incurred.

Impairment of Long-Lived Assets

Long-lived assets consist primarily of property and equipment and right-of-use assets (ROU) associated with our operating and financing leases. An impairment loss is recorded if and when events and circumstances indicate that assets might be impaired and the undiscounted cash flows estimated to be generated by those assets are less than the carrying amount of those assets. While our current and historical operating losses are indicators of impairment, we believe that future cash flows to be received support the carrying value of our long-lived assets and, accordingly, havenot recognized any impairment losses since inception.

Accrued Expenses

Accrued expenses include salaries, wages, benefits costs, consulting fees, legal and research and development costs. We have entered into contractual arrangements related to our clinical studies with clinical research organizations (CROs) and contracted development and manufacturing organizations (CDMOs) and recognize expense based on work completed and efforts expended pursuant to our contractual arrangements. We make estimates of our accrued CRO costs as of each balance sheet date based on facts and circumstances known at the time and include total trial management costs, sites activated, patients enrolled and number of patient visits. We estimate the time period over which services will be performed and the level of effort to be expended in each period. There may be instances in which payments made to our service providers including CROs and CDMOs, will temporarily exceed the level of services provided and result in a prepayment of the expense. If the actual timing of the performance of services or the level of effort varies from our estimate, we adjust the accrual or prepaid expense balance accordingly. Historically, our estimated accrued liabilities have materially approximated actual expenses incurred.

Leases

We determine if an arrangement is a lease at inception. Short-term leases with an initial term of 12 months or less are not recorded on our balance sheet. For long-term leases with an initial term of greater than 12 months, we recognize a right-of-use asset (ROU) and a lease liability based on the present value of future lease payments using an estimated rate of interest that we would pay to borrow equivalent funds on a collateralized basis at the lease commencement date. We determine the lease term at the commencement date by considering whether renewal options and termination options are reasonably assured of exercise. Rent expense for operating leases is recognized on a straight-line basis over the lease term and is included in operating expenses in our consolidated statements of operations. For financing leases, interest expense and amortization of the ROU is included in operating expenses in our consolidated statements of operations and variable lease payments are recorded as incurred.

If a lease is modified, the modified contract is evaluated to determine whether it is or contains a lease. If a lease continues to exist, the lease modification is determined to be a separate contract when the modification grants the lessee an additional ROU that is not included in the original lease and the lease payments increase commensurate with the standalone price for the additional ROU. A lease modification that results in a separate contract will be accounted for in the same manner as a new lease. For a modification that is not a separate contract, we reassess the lease classification using the modified terms and conditions and the facts and circumstances as of the effective date of the modification and recognize the amount of the remeasurement of the lease liability for the modified lease as an adjustment to the corresponding lease ROU asset.

Our ROU assets consist of a non-cancelable operating lease for our corporate headquarters and financing leases for various research and development and information technology equipment.

We do not separate lease and non-lease components for our long-term leases.

Revenue Recognition

We evaluate our agreements under ASC Topic 606, Revenue from Contracts with Customersand ASC Topic 808, Collaborative Arrangements. We recognize revenue when we transfer promised goods or services to customers in an amount that reflects the consideration to which we expect to be entitled in exchange for those goods or services. In determining the appropriate amount of revenue to be recognized as we fulfill our obligations under our agreement, we perform the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) we satisfy each performance obligation. As part of the accounting for these arrangements, we must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. We use key assumptions to determine the stand-alone selling price, which may include forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success.

We recognize revenue in one of two ways, over time or at a point in time. We recognize revenue over time when we are executing on our performance obligation over time and our partner receives benefit over time. For example, we recognize revenue over time when we provide research and development services. We recognize revenue at a point in time when we transfer control of a distinct performance obligation to our partner. For example, if a license to our intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, we recognize revenues from non-refundable, up-front fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license.

Research and Development Costs

Research and development costs are expensed as incurred. Research and development costs include: salaries and employee-related expenses, including stock-based compensation and benefits for personnel in research and product development functions; costs associated with conducting our preclinical, development and regulatory activities, including fees paid to third-party professional consultants, service providers and our scientific, therapeutic and clinical advisors; costs to acquire, develop and manufacture preclinical study and clinical trial materials; costs incurred under clinical trial agreements with CROs and investigative sites; costs for laboratory supplies; payments related to licensed products and technologies; allocated facilities and information technology costs; and depreciation.

Patent Costs

Costs related to filing and pursuing patent applications are recorded as general and administrative expense and expensed as incurred since recoverability of such expenditures is uncertain.

Stock-Based Compensation

We evaluate our stock-based compensation arrangements under ASC Topic 718, Compensation – Stock Compensation. Stock-based compensation expense represents the grant date fair value of employee stock option and restricted stock unit grants recognized as expense over the requisite service period of the awards (usually the vesting period) on a straight-line basis. We estimate fair value of stock option grants using the Black-Scholes option pricing model. We estimate the fair value using assumptions, including the risk-free interest rate, the expected volatility of a peer group of similar companies, the expected term of the awards and the expected dividend yield. These estimates involve inherent uncertainties and the application of management’s judgment. If factors change and different assumptions are used, our stock-based compensation expense could be materially different in the future.

Income Taxes

We account for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the consolidated financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the consolidated financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized as income in the period that includes the enactment date.

We recognize net deferred tax assets to the extent that we believe these assets are more likely than not to be realized. In making such a determination, we consider all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies and results of recent operations. If we determine that we would be able to realize the deferred tax assets in the future in excess of their net recorded amount, we would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes.

We record uncertain tax positions on the basis of a two-step process whereby (1) we determine whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, we recognize the largest amount of tax benefit that is more than 50% likely to be realized upon ultimate settlement with the related tax authority. We recognize interest and penalties related to unrecognized tax benefits within income tax expense. Any accrued interest and penalties are included within the related tax liability.

Net Loss Per Share

Basic net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted average number of common stock and common stock equivalents outstanding for the period determined using the treasury-stock method. Dilutive common stock equivalents are comprised of convertible preferred stock, warrants for common stock, stock options and restricted stock units outstanding under our stock option plans and inducement grants and estimated shares to be purchased under our 2015 Employee Stock Purchase Plan (the 2015 ESPP). For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding due to our net loss position.

Potentially dilutive securities not included in the calculation of diluted net loss per share because to do so would be anti-dilutive are as follows (in common share equivalents):

The following table summarizes our net loss per share (in thousands, except per share data):

Recent Accounting Pronouncements

In November 2023, the Financial Accounting Standards Board (FASB) issued Accounting Standard Update (ASU) 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which requires public entities to disclose information about their reportable segments’ significant expenses and other segment items on an interim and annual basis. Public entities with a single reportable segment are required to apply the disclosure requirements in ASU 2023-07, as well as all existing segment disclosures and reconciliation requirements in ASC 280 on an interim and annual basis. Weadopted ASU 2023-07 during the year ended December 31, 2024. See Note 1, Segment Reporting, in the accompanying notes to the consolidated financial statements for further detail.

In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures, which requires entities to disclose disaggregated information about their effective tax rate reconciliation as well as expanded information on income taxes paid by jurisdiction. The disclosure requirements will be applied on a prospective basis, with the option to apply them retrospectively. The standard is effective for fiscal years beginning after December 15, 2024, with early adoption permitted. We are currently evaluating the disclosure requirements related to the new standard and expect that the adoption willnot have a material impact on our consolidated financial statements.

3. Fair Value Measurements

The carrying amounts of cash equivalents, prepaid and other assets, accounts payable and accrued liabilities are considered to be representative of their respective fair values because of the short-term nature of those instruments. Investment securities are recorded at fair value.

The accounting guidance defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or nonrecurring basis. Fair value is defined as an 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 such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the accounting guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows:

Level 1: Observable inputs such as quoted prices in active markets.

Level 2: Inputs, other than the quoted prices in active markets that are observable either directly or indirectly.

Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions.

Financial assets measured at fair value on a recurring basis consist of investment securities. Investment securities are recorded at fair value, defined as the exit price in the principal market in which we would transact, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. Level 2 securities are valued using quoted market prices for similar instruments, non-binding market prices that are corroborated by observable market data, or discounted cash flow techniques and include our investments in commercial paper, corporate debt securities and U.S. government agencies. We have no financial liabilities measured at fair value on a recurring basis. None of our non-financial assets and liabilities are recorded at fair value on a non-recurring basis. No transfers between levels have occurred during the periods presented.

Assets measured at fair value on a recurring basis are as follows (in thousands):

As of December 31, 2024 and 2023, available-for-sale investments are detailed as follows (in thousands):

We evaluate our available-for-sale debt securities for credit losses when the amortized cost basis exceeds fair value. The credit-related portion of unrealized losses, and any subsequent improvements, are recorded in interest income through an allowance account. Unrealized gains and losses that are not credit-related are included in accumulated other comprehensive income (loss). When evaluating an investment for impairment, we review factors such as the severity of the impairment, changes in underlying credit ratings, our intent to sell or the likelihood that we would be required to sell the investment before its anticipated recovery in market value and the probability that the scheduled cash payments will continue to be made. Based on our evaluation, we did not record allowance for credit losses in the consolidated statement of operations during the year ended December 31, 2024.

As of December 31, 2024, all available-for-sale investments had effective maturity dates of less thanone year. As of December 31, 2024,11 out of 22 available-for-sale investments were in a gross unrealized loss position of whichone available-for-sale investment with a market value of $1.0 million was in such position for greater than 12 months.

As of December 31, 2024 and 2023, accrued interest receivable on available-for-sale securities for each of the periods was $0.2 million and $0.3 million, respectively.

4. License and Collaboration Agreements

Kyorin Pharmaceutical Co., Ltd.

In January 2020, we entered into a collaboration and license agreement (Kyorin Agreement) with Kyorin Pharmaceutical Co., Ltd. (Kyorin) for the development and commercialization of efzofitimod for the treatment of interstitial lung disease (ILD) in Japan. Under the Kyorin Agreement, Kyorin received an exclusive right to develop and commercialize efzofitimod in Japan for all forms of ILD, and is obligated to fund all research, development, regulatory, marketing and commercialization activities in Japan. In 2020, Kyorin conducted and funded a Phase 1 clinical trial of efzofitimod (known as KRP-R120 in Japan). The Phase 1 clinical trial was a placebo-controlled clinical trial to evaluate the safety, pharmacokinetics (PK) and immunogenicity of efzofitimod in 32 healthy Japanese male volunteers. Efzofitimod was observed to be generally well-tolerated with no drug-related serious adverse events, and PK findings were consistent with previous studies of efzofitimod. Kyorin is also participating in the EFZO-FIT study as the local sponsor in Japan. In February 2023, Kyorin dosed the first patient in Japan in the EFZO-FIT study which triggered a $10.0 million milestone payment to us. To date, the Kyorin Agreement has generated $20.0 million in upfront and milestone payments to us and we are eligible to receive up to an additional $155.0 million in the aggregate upon achievement of certain development, regulatory and sales milestones, as well as tiered royalties on any net sales in Japan.

Either party may terminate the Kyorin Agreement in the event that the other party breaches the agreement and fails to cure the breach, becomes insolvent or challenges certain of the intellectual property rights licensed under the agreement.

We assessed our license and collaboration with Kyorin in accordance with Topic 606 and concluded that Kyorin is a customer. We identified the following performance obligations under the Kyorin Agreement: 1) the license of efzofitimod for ILD in Japan; and 2) free clinical trial material for Kyorin’s Phase 1 clinical trial. Kyorin is participating in the EFZO-FIT study and received approval from the Pharmaceuticals and Medical Devices Agency (PMDA) to commence the EFZO-FIT study in Japan in December 2022. Additionally, in February 2023, Kyorin dosed the first patient in Japan in the EFZO-FIT study which triggered a $10.0 million milestone payment to us. We recognized this $10.0 million milestone payment as revenue during the year ended December 2022, as we determined the milestone became probable of achievement with Kyorin having scheduled site visits for patient screenings by that time. We received this $10.0 million milestone payment in February 2023. During the years ended December 31, 2024 and 2023, we recognized $0.2 million and $0.4 million, respectively, in collaboration revenue from Kyorin for drug product material sold to Kyorin for the Japan portion of the EFZO-FIT study.

The remaining milestones and royalty payments under the Kyorin Agreement are variable consideration. Since the milestone payments are binary in nature, we will use the “most-likely” method to evaluate whether the milestones should be included as revenue. We will constrain these amounts until they become probable of being achieved. The royalties are dependent on future sales by Kyorin which are at the full discretion of Kyorin. Accordingly, we will apply a constraint to these amounts until the future sale sales have occurred.

5. Balance Sheet Details

Prepaid expenses consist of the following (in thousands):

Property and equipment consist of the following (in thousands):

During the years ended December 31, 2024, 2023 and 2022, depreciation expense was $0.7 million, $0.6 million and $0.2 million, respectively.

Accrued expenses consist of the following (in thousands):

6. Commitments and Contingencies

Operating Leases

Corporate Headquarters Facility Lease

In May 2022, we entered into a lease (the Lease) with San Diego Creekside, LLC (Landlord), as lessor, pursuant to which we agreed to lease from Landlord approximately 23,696 rentable square feet (subject to increase pursuant to the terms of the Lease) of office and laboratory space. The term of the lease (the Lease Term) commenced on March 20, 2023 (the Lease Commencement Date) and will continue for 124 months from the Lease Commencement Date. We also have one option toextend the Lease Term forfive years. Base rent during such extension period would be at the fair market rent for the Premises (as that term is defined in the Lease). Under the terms of the Lease, the base rent during the first 12 months of the Lease Term was $5.75 per square foot of rentable area per month, and the base rent following the first 12 months of the Lease Term is subject to certain upward adjustments of approximately 3.0% annually. We received $5.3 million in allowance payments for tenant improvements, which represents the full allowance to which we were entitled under the Lease. We provided a $0.7 million security deposit in the form of a letter of credit which is included in restricted cash as of December 31, 2024. During the second quarter of 2023, additional common area amenities were completed by the Landlord which provided us with access to an estimated 1,500 additional rentable square feet. In April 2024, we finalized an amendment to the Lease (the Lease Amendment), effective June 2023. The additional rentable square feet was adjusted to 1,170 square feet for a total of 24,866 rentable square feet and our base rent increased for this additional rentable square feet at the same monthly base rent per rentable square foot as contemplated in the Lease.

Future minimum payments under the facility lease and reconciliation to the operating lease liability as of December 31, 2024 were as follows (in thousands):

Operating lease expense was $1.5 million, $1.9 million and $1.5 million for the years ended December 31, 2024, 2023 and 2022, respectively. As of December 31, 2024 and 2023, the weighted average remaining lease term was 8.6 years and 9.4 years, respectively. As of December 31, 2024 and 2023, the weighted average discount rate for each period was 8.8%.

Financing Leases

In April 2022, we entered into a master financing lease agreement to lease various research and development and information technology equipment over a 48-month term. Future minimum payments under the financing lease and reconciliation to the financing lease liability as of December 31, 2024 were as follows (in thousands):

As of December 31, 2024 and 2023, the weighted-average remaining lease term was 2.1 years and 3.0 years, respectively, and the weighted-average discount rate for each period was 8.3%. We provided a $2.3 million deposit to be held as collateral for the leased equipment, and this deposit is included in restricted cash as of December 31, 2024.

7. Stockholders’ Equity

Underwritten Follow-On Public Offerings

In February 2023, we completed an underwritten follow-on public offering of 23,125,000 shares of our common stock, including the partial exercise of the underwriters’ option to purchase additional shares, at a price to the public of $2.25 per share. The total net proceeds from the offering were approximately $48.1 million, after deducting underwriting discounts, commissions and offering expenses payable by us.

At-the-Market Offering Programs

In April 2022, we entered into an Open Market Sale Agreement SM with Jefferies LLC (Jefferies) implementing an “at-the-market” offering program, (the Jefferies ATM Offering Program). In December 2024, we amended the Jefferies ATM Offering Program. Under the Jefferies ATM Offering Program we may offer and sell, from time to time and at our option, up to an aggregate of $215.0 million of shares of our common stock (inclusive of $65.0 million of sales made prior to the amendment) through Jefferies, acting as sales agent. Jefferies is entitled to a fixed commission rate of up to 3.0% of the gross sales proceeds of shares sold under the Jefferies ATM Offering Program. During the year ended December 31, 2023, we sold an aggregate of 10,530,795 shares of common stock at a weighted-average price of $1.82 per share for net proceeds of approximately $18.4 million under the Jefferies ATM Offering Program. During the year ended December 31, 2024, we sold an aggregate of 20,653,450 shares of common stock at a weighted-average price of $2.02 per share for net proceeds of approximately $40.3 million under the Jefferies ATM Offering Program.

2014 Stock Plan

We adopted a stock option plan in 2007 (the 2007 Plan), which was subsequently amended, restated and renamed in July 2014 (the 2014 Plan) to provide for the incentive stock options, nonstatutory stock options, stock and rights to purchase restricted stock to eligible recipients. Recipients of incentive stock options are eligible to purchase shares of our common stock at an exercise price equal to no less than the estimated fair market value of such stock on the date of grant. The maximum term of the stock options under the 2014 Plan isten years. Stock options granted generally vest over four years. We ceased granting under the 2014 Plan after our IPO in May 2015. Shares underlying any awards under the 2014 Plan that are forfeited, canceled, reacquired by us prior to vesting, satisfied without the issuance of stock or otherwise terminated (other than by exercise) will be added to shares available for issuance under our 2015 Stock Option and Incentive Plan (the 2015 Stock Plan), which became effective in May 2015.

2015 Stock Plan

Total shares available for issuance under the 2015 Stock Plan as of December 31, 2024 were 4,931,323. Shares underlying any awards under the 2015 Stock Plan that are forfeited, canceled, reacquired by us prior to vesting, satisfied without the issuance of stock or otherwise terminated (other than by exercise) will be added to shares available for issuance under the 2015 Stock Plan.

The maximum term of stock options granted under 2015 Stock Plan isten years. For an initial grant to an employee,25% of the stock options generally vest on the first anniversary of the original vesting date, with the balance vesting monthly over the remaining three years. For subsequent grants to an employee, the stock options generally vest monthly over afour-year term.

Inducement Plan and Grants

In March 2022, our board of directors approved and adopted our 2022 Inducement Plan (our Inducement Plan). Awards granted under our Inducement Plan are in accordance with Nasdaq Listing Rule 5635(c)(4). A total of 300,000 shares of our common stock were reserved for the issuance under our Inducement Plan.

The maximum term of stock options granted under our Inducement Plan isten years. Each option vests over a period offour years, with 25% of the shares vesting on theone-year anniversary of the applicable vesting commencement date and the remaining 75% vesting in equal monthly installments over three years, thereafter, subject to continuous employment.

During the year ended December 31, 2024, we granted nonstatutory stock options under our Inducement Plan to purchase an aggregate of 9,400 shares of our common stock, with a weighted-average exercise price of $1.86 per share as inducement awards to new employees.

In August 2024, we granted a nonstatutory option to purchase 150,000 shares of our common stock at an exercise price of $1.88 per share as an inducement award in connection with the hiring of our Vice President, Technical Operations. We filed a registration statement on Form S-8 to register the shares of common stock underlying this option prior to the time that this option becomes exercisable.

2015 Employee Stock Purchase Plan

As of December 31, 2024, total shares reserved for issuance under the 2015 ESPP were 650,354.

Stock-based Compensation

Stock Options

Stock option activity is summarized as follows:

The assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee stock option grants were as follows:

The assumptions used in the Black-Scholes option pricing model to determine the fair value of the ESPP offering were as follows:

Expected term. The expected term represents the period of time that stock options are expected to be outstanding. Because we do not have sufficient history of exercise behavior, we determine the expected life assumption using the simplified method, which is an average of the contractual term of the option and its vesting period.

Risk-free interest rate. We base the risk-free interest rate assumption on the U.S. Treasury’s rates for U.S. Treasury zero-coupon bonds with maturities similar to those of the expected term of the award being valued.

Expected volatility. The expected volatility assumption is based on our historical volatility.

Expected dividend yield. We base the expected dividend yield assumption on the fact that we have never paid cash dividends and have no present intention to pay cash dividends.

Restricted Stock Units

Occasionally, we grant restricted stock units to employees. The fair value of restricted stock is determined by the closing price of our common stock reported on the Nasdaq Capital Market on the date of grant. Restricted stock unit activity is summarized as follows:

The allocation of stock-based compensation for all stock options and restricted stock units is as follows (in thousands):

The weighted-average grant date fair value per share of stock options granted by us, during the years ended December 31, 2024, 2023 and 2022 was $1.16,$1.59 and $2.49, respectively. There wereno restricted stock units granted by us during the years ended December 31, 2024 and 2023. The total grant date fair value of restricted stock units granted by us during the year ended December 31, 2022, was approximately $597,000. There wereno stock options exercised during the years ended December 31, 2024 and 2023. The aggregate intrinsic value of stock options exercised during the year ended December 31, 2022 was approximately $1,000. The fair value of restricted stock units released during the years ended December 31, 2024, 2023 and 2022 was approximately $37,000, $124,000 and $6,000, respectively. As of December 31, 2024, total unrecognized share-based compensation expense related to unvested stock options and restricted stock units was approximately $4.3 million and $0.1 million, respectively. As of December 31, 2024, these unrecognized costs for stock options and restricted stock units are expected to be recognized ratably over a weighted-average period of approximately 2.2 years and 1.0 years, respectively.

Common Stock Reserved for Future Issuance

Common stock reserved for future issuance was as follows:

8. Income Tax

Pretax losses were generated by both domestic and foreign operations as follows (in thousands):

For the years ended December 31, 2024, 2023, and 2022, we didnot record a provision for income taxes due to a full valuation allowance against our deferred taxes. A reconciliation of the expected statutory federal income tax provision to the actual income tax provision is summarized as follows (in thousands):

Deferred income taxes are provided for temporary differences in recognizing certain income and expense items for financial and tax reporting purposes. The deferred tax assets consisted primarily of the income tax benefits from net operating loss (NOL) carryforwards, research and development credits and capitalized research and development expenses, along with other accruals and reserves. Valuation allowances of $124.2 million and $108.0 million as of December 31, 2024 and 2023, respectively, have been recorded to offset deferred tax assets as realization of such assets does not meet the more-likely-than-not threshold under ASC 740, Accounting for Income Taxes.

Significant components of our deferred tax assets are summarized as follows (in thousands):

The Tax Cuts and Jobs Act of 2017 requires taxpayers to capitalize and amortize research and development (R&D) expenditures under section 174 for tax years beginning after December 31, 2021. This rule was effective at the beginning of 2022 which resulted in a capitalization of R&D costs of approximately $54.5 million and $44.2 million during the years ended December 31, 2024 and 2023, respectively. We will amortize these costs for tax purposes over 5 years if the R&D was performed in the U.S. and over 15 years if the R&D was performed outside the U.S.

As of December 31, 2024, we had federal NOL carryforwards of approximately $298.9 million, with $186.4 million of NOLs generated after December 31, 2017 carrying forward indefinitely and $112.5 million of NOLs that will begin to expire in 2025. NOL carryforwards generated after January 1, 2018 are subject to an 80% of taxable income limitation in accordance with the Tax Cuts and Jobs Act of 2017. We had state net operating loss carryforwards of approximately $258.3 million, and foreign net operating loss carryforwards of $9.4 million. The state net operating losses will begin to expire in 2025. The foreign net operating losses carry over indefinitely.

As of December 31, 2024, we had federal and state research and development credit carryforwards of approximately $11.0 million and $6.4 million, respectively, which will begin to expire in 2026 for both federal and state purposes. We had $23.1 million of federal Orphan Drug Credits as of December 31, 2024, which will begin to expire in 2035.

Utilization of the domestic NOL and research and development credit carryforwards may be subject to a substantial annual limitation due to ownership change limitations that may have occurred or that could occur in the future, as required by Sections 382 and 383 of the Internal Revenue Code of 1986, as amended (the Code), as well as similar state and foreign provisions. These ownership changes may limit the amount of NOL and research and development credit carryforwards that can be utilized annually to offset future taxable income and tax, respectively. In general, an “ownership change” as defined by Section 382 of the Code results from a transaction or series of transactions over athree-year period resulting in an ownership change of more than 50 percentage points of the outstanding stock of a company by certain stockholders. Since the Company’s formation, we raised capital through the issuance of capital stock on several occasions which on its own or combined with the purchasing stockholders’ subsequent disposition of those shares, has resulted in such an ownership change, and could result in an ownership change in the future.

Upon the occurrence of an ownership change under Section 382 as outlined above, utilization of the NOL and research and development credit carryforwards become subject to an annual limitation under Section 382 of the Code, which is determined by first multiplying the value of our stock at the time of the ownership change by the applicable long-term, tax-exempt rate, which could be subject to additional adjustments. Any limitation may result in expiration of a portion of our NOL or research and development credit carryforwards before utilization. Due to the existence of the valuation allowance, any impact to the NOL and research and development tax credit carryforwards from Section 382 analysis will be offset by a corresponding adjustment to valuation allowance, resulting in no tax provision impact.

We recognize a tax benefit from an uncertain tax position when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, based on the technical merits. Income tax positions must meet a more-likely-than-not recognition threshold to be recognized.

Our practice is to recognize interest and penalties related to income tax matters in income tax expense. We hadno accrual for interest and penalties on our balance sheet and had not recognized interest or penalties in the consolidated statements of operations for the years ended December 31, 2024, 2023 and 2022.

Due to the existence of the valuation allowance, future changes in unrecognized tax benefits will not impact our effective tax rate.

Uncertain tax positions are evaluated based upon the facts and circumstances that exist at each reporting period. Subsequent changes in judgment based upon new information may lead to changes in recognition, derecognition, and measurement. Adjustments may result, for example, upon resolution of an issue with the taxing authorities, or expiration of a statute of limitations barring an assessment for an issue.

The activity related to our unrecognized tax benefits is summarized as follows (in thousands):

We donot anticipate that the amount of unrecognized tax benefits as of December 31, 2024 will change within the next twelve months.

We are subject to taxation in the United States, Hong Kong and state jurisdictions. Our tax years from inception are subject to examination by the United States, Hong Kong and various state authorities due to carry forward of unutilized NOLs and research and development credits.

9. Employee Benefits

401(k) Plan

We maintain a defined contribution 401(k) plan available to eligible employees. Employee contributions are voluntary and are determined on an individual basis, limited to the maximum amount allowable under federal tax regulations. In April 2015, our board of directors approved a policy, beginning on June 1, 2015, to match employee contributions equal to 50% of the participant’s contribution of up to a maximum of 6% of the participant’s annual salary. We made discretionary contributions totaling $0.2 million during each of the years ended December 31, 2024, 2023 and 2022.

10. Subsequent Events

Sales of Common Stock through the Jefferies ATM Offering Program

From January 1, 2025 through March 12, 2025, we sold an aggregate of 4,797,682 shares of common stock at a weighted-average price of $3.92 per share through the Jefferies ATM Offering Program for net proceeds of $18.3 million.