1. Organization, Business, Basis of Presentation and Summary of Significant Accounting Policies

Unaudited Interim Financial Information

The accompanying interim unaudited condensed consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles (U.S. GAAP) and follow the requirements of the U.S. Securities and Exchange Commission (SEC) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. In our opinion, the unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements and include all adjustments, which include only normal recurring adjustments, necessary for the fair presentation of our financial position and our results of operations and cash flows for periods presented. These statements do not include all disclosures required by U.S. GAAP and should be read in conjunction with our financial statements and accompanying notes for the fiscal year ended December 31, 2023, contained in our Annual Report on Form 10-K filed with the SEC on March 14, 2024. The results of the interim periods are not necessarily indicative of the results expected for the full fiscal year or any other interim period or any future year or period.

Risks and Uncertainties

Global economic and business activities continue to face widespread macroeconomic uncertainties, including global geopolitical tension, armed conflicts, potential future health pandemics, labor shortages, inflation and monetary supply shifts, liquidity concerns at, and failures of, banks and other financial institutions or other disruptions in the banking system or financing markets, higher interest rates and financial and credit market fluctuations, volatility in the capital markets and recession risks, which has resulted in further volatility in the U.S. and global financial markets and which has led to and may continue to lead to, additional disruptions to trade, commerce, pricing stability, credit availability and supply chain continuity globally. The ultimate long-term impact of these evolving geopolitical and macroeconomic conditions on our business is uncertain, although we continue to actively monitor the impact of these factors on our results of operations, financial condition and cash flows. The extent of the impact of these factors on our operational and financial performance, including our ability to execute our business strategies and initiatives in the expected timeframe, will depend on future developments, which are uncertain and cannot be predicted; however, any continued or renewed disruption resulting from these factors could negatively impact our business.

Liquidity and Financial Condition

We have incurred net losses and negative cash flows from operations since our inception in 2005, including a consolidated net loss of $15.5 million for the three months ended March 31, 2024. As of March 31, 2024, we had an accumulated deficit of $483.5 million. We believe that our existing cash, cash equivalents, restricted cash and available-for-sale investments of $87.7 million as of March 31, 2024 will be sufficient to meet our material cash requirements from known contractual and other obligations for a period of at least one year from the filing date of this Quarterly Report on Form 10-Q.

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.

Employee Retention Credit

On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (CARES Act) was signed into law providing numerous tax incentives and other stimulus measures, including an employee retention credit (ERC), which is a refundable tax credit against certain employment taxes. The Taxpayer Certainty and Disaster Tax Relief Act of 2020 and the American Rescue Plan Act of 2021 extended and expanded the availability of the ERC.

As a result of the foregoing legislation, we determined that we are eligible to claim an ERC benefit on qualified wages that we paid to our employees between March 2020 and September 2021. Our credit was primarily derived from qualified wages during January 2021 through September 2021 based on gross receipts for each calendar quarter in 2021 compared to the corresponding calendar quarter in 2019. We determined that we had met the requirement for a decline in gross receipts.

Accounting Standards Codification (ASC) Topic 105, Generally Accepted Accounting Principles describes the decision-making framework when no guidance exists in U.S. GAAP for a particular transaction. Specifically, ASC 105-10-05-2 instructs companies to look for guidance for a similar transaction within U.S. GAAP and apply that guidance by analogy. We accounted for the ERC by analogy to International Accounting Standards (IAS) 20, Accounting for Government Grants and Disclosure of Government Assistance, of International Financial Reporting Standards (IFRS). Under an IAS 20 analogy, a business entity would recognize the credit on a systematic basis over the periods in which the entity recognizes the payroll expenses for which the ERC is intended to compensate when there is reasonable assurance that the entity will comply with any conditions attached to the ERC and the ERC will be received.

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.

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 unaudited condensed 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 prepaid expenses and other current assets on our unaudited condensed 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.

Use of Estimates

Our unaudited condensed consolidated financial statements are prepared in accordance with U.S. GAAP. The preparation of our unaudited condensed 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 unaudited condensed consolidated financial statements and accompanying notes. The most significant estimates in our unaudited condensed consolidated financial statements relate to 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.

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 unaudited condensed consolidated statements of operations. For financing leases, interest expense and amortization of the ROU is included in operating expenses in our unaudited condensed consolidated statements of operations and variable lease payments are expensed 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 ROU asset.

Our ROU assets consist of non-cancelable operating leases and financing leases. Non-cancelable operating leases consist of leases for our corporate headquarters and additional laboratory space. Financing leases consist of 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 Customers and 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.

Net Loss Per Share

Basic net loss per share is calculated by dividing the net loss by the weighted-average number of common shares outstanding for the period. Diluted net loss per share is calculated by dividing the net loss by the weighted-average number of common stock equivalents outstanding for the period determined using the treasury-stock method. Dilutive common stock equivalents are comprised of warrants for common stock, options and restricted stock units outstanding under our stock option plans and estimated shares to be purchased under our employee stock purchase plan. 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 considered for the calculation of diluted net loss per share are as follows (in common stock equivalents):


	March 31,
	2024		2023
Common stock warrants		5,864		13,760
Common stock options and restricted stock units		5,712,725		3,922,930
Employee stock purchase plan		41,862		34,588
Total		5,760,451		3,971,278