In accordance with Accounting Standards Codification ("ASC"), Subtopic 730-10-25,Accounting for Research and Development Costs, the up-front payments to acquire a new drug compound, as well as future milestone payments when paid or payable, are immediately expensed as acquired IPR&D in transactions other than a business combination provided that the drug has not achieved regulatory approval for marketing and, absent obtaining such approval, has no alternative future use. Therefore, the portion of the purchase price that was allocated to the IPR&D assets acquired was immediately expensed. Other assets acquired and liabilities assumed, were recorded at fair value. The Company also recorded a $0.8 million income tax benefit for the year ended December 31,2022, related to research and development credits that are expected to be realized from the local jurisdiction in Denmark. 

The following represents the consideration paid and purchase price allocation for the acquisition of arimoclomol (in thousands):

Amendment to Registration Statement on Form S-3

On January 25, 2022, the Company filed an amendment to the registration statement on Form S-1 (File No.333-250945) on Form S-3 covering the issuance of the shares of the Company's common stock issuable upon the exercise of the warrants issued in the Company's January 2021 underwritten public offering (the "Public Offering") and remaining unexercised as of the date of the amendment, which was declared effective on February 1, 2022.

On March 1, 2023, following its name change, the Company's common stock began trading on the Nasdaq Global Select Market under the ticker symbol "ZVRA".

Going Concern

The accompanying unaudited condensed consolidated financial statements have been prepared on a going concern basis, which contemplates the realization of assets and the satisfaction of liabilities in the normal course of business. During the three months ended March 31,2024, and 2023, the Company incurred a net loss of $16.6 million and $13.2 million, respectively, and as of March 31,2024, has an accumulated deficit of $416.4 million. The Company has sustained operating losses for the majority of its corporate history and expects to continue to incur operating losses and negative operating cash flows until revenues reach a level sufficient to support ongoing operations.

The Company’s ability to continue operating as a going concern is contingent upon its ability to generate revenue from approved products or obtain product candidate regulatory approvals, which would generate revenue, milestones, and cash flow sufficient to support ongoing operations and the satisfaction of financial covenants. These factors raise substantial doubt as to the Company’s ability to continue as a going concern for at least one year from the date the unaudited condensed consolidated financial statements are being issued. The unaudited condensed consolidated financial statements do not include any adjustments that might result from the outcome of these uncertainties.

The Company's liquidity needs will be largely determined by the success of operations through the progression of its products and product candidates in the future. The Company also may consider other sources to fund operations including: (1) out-licensing rights to certain of its technologies and product candidates, pursuant to which the Company would receive cash royalties and milestones; (2) raising additional capital through equity or debt financings or from other sources; (3) obtaining product candidate regulatory approvals, which would generate revenue, milestones and cash flow; (4) reducing spending on one or more research and development programs, including by discontinuing development; and/or (5) restructuring operations to change its overhead structure. The Company is in the early stages of its commercialization effort for OLPRUVA and does not yet have a substantial basis to project future earnings, and its other sources of revenue are not sufficient to sustain its present activities on their own. Accordingly, the Company's ability to continue as a going concern may require it to obtain additional financing to fund its operations.

Basis of Presentation

The Company prepared the unaudited condensed consolidated financial statements in accordance with U.S. GAAP and the rules and regulations of the Securities and Exchange Commission ("SEC") and, in the Company's opinion, reflect all adjustments, including normal recurring items that are necessary.

Merger

On August 30, 2023, the Company and Aspen Z Merger Sub, Inc., a wholly-owned subsidiary of Zevra (“Merger Sub”), entered into an Agreement and Plan of Merger (the “Merger Agreement”) with Acer Therapeutics Inc. (“Acer”), a pharmaceutical company focused on development and commercialization of therapies for rare and life-threatening diseases. On November 17, 2023 (the "Closing Date"), the Company completed the acquisition of Acer. Pursuant to the Merger Agreement, on the Closing Date, Merger Sub was merged with and into Acer (the "Merger"), with Acer continuing as the surviving entity and as a wholly-owned subsidiary of Zevra. In connection therewith, Zevra also purchased Acer’s secured debt from Nantahala Capital Management, LLC ("NCM”), certain of its affiliates and certain other parties (collectively with NCM, “Nantahala”) through a series of transactions and Zevra agreed to provide Acer with a bridge loan facility for up to $18.0 million ("Bridge Loan"), subject to certain terms and conditions. The Merger expanded Zevra's rare disease portfolio, as well as increased and diversified its revenues with the addition of a U.S. commercial asset, OLPRUVA, indicated for the treatment of UCDs. See Note L for further discussion related to the Merger.

Amendment to Registration Statement on Form S-3

In connection with the Merger, Zevra and Nantahala concurrently entered into a registration rights agreement, pursuant to which Zevra agreed to file a resale registration statement with respect to the resale of the Zevra common stock issuable to Nantahala. On February 5, 2024, Zevra filed a registration statement on Form S-3 (File No.333-276856) registering an aggregate of 2,269,721 shares of Zevra’s common stock.

On April 5, 2024, we filed an amendment to the registration statement on Form S-3 (File No.333-250945) covering the issuance of the shares of our common stock issuable upon the exercise of warrants issued in connection with the Merger (Note L) and remaining unexercised as of the date of the amendment, which was declared effective on April 8, 2024.

Entry into 2021 ATM Agreement

On July 2, 2021, the Company entered into an equity distribution agreement (the "2021 ATM Agreement") with JMP Securities LLC ("JMP") and RBC Capital Markets, LLC ("RBCCM") under which the Company may offer and sell, from time to time at its sole discretion, shares of its common stock having an aggregate offering price of up to $75.0 million through JMP and RBCCM as its sales agents. The issuance and sale, if any, of common stock by the Company under the 2021 ATM Agreement will be made pursuant to a registration statement on Form S-3. JMP and RBCCM may sell the common stock by any method permitted by law deemed to be an “at the market offering” as defined in Rule 415 of the Securities Act of 1933, as amended. JMP and RBCCM will use commercially reasonable efforts to sell the common stock from time to time, based upon instructions from the Company (including any price, time or size limits or other customary parameters or conditions the Company may impose). The Company will pay JMP and RBCCM a commission equal to 3.0% in the aggregate of the gross sales proceeds of any common stock sold through JMP and RBCCM under the 2021 ATM Agreement. The Company filed a registration statement on Form S-3 covering the sale of the shares of its common stock up to $350.0 million, $75.0 million of which was allocated to the sales of the shares of common stock issuable under the 2021 ATM Agreement, which was declared effective on July 12, 2021. As of March 31, 2023,2024, no shares have been issued or sold under the 2021 ATM Agreement.

Share Repurchase Program

On December 20, 2021, the Company initiated a share repurchase program (the "Share Repurchase Program") pursuant to which the Company may was able to repurchase up to $50 million of shares of its common stock through December 31, 2023. Capital allocation to On December 31, 2023, the Share Repurchase Program will be based on a variety of factors, including the Company's business results, the receipt of royaltiesended, and sales milestones under the AZSTARYS License Agreement (refer to Note B), and potentially other sources of non-dilutive capital that may become available to the Company. Repurchases will be made in compliance with Rule 10b-18 of the Securities Exchange Act of 1934, as amended, subject to a variety of factors, including the market price of the Company’s common stock, general market and economic conditions and applicable legal requirements. The exact number of shares to be repurchased by the Company is not guaranteed and the program may be suspended, modified, or discontinued at any time without prior notice. As of March 31, 2023, the Company had repurchasedrepurchased 1,575,692 shares of its common stock for approximately $11.0 million under the Share Repurchase Program.

Reclassifications

Certain reclassifications were made to the 2022 unaudited condensed consolidated financial statements to conform to the classifications used in 2023. These reclassifications had no impact on the consolidated net loss, changes in stockholder's equity, or cash flows previously reported.million.

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires the Company to make estimates and assumptions that affect the amounts reported in the unaudited condensed consolidated financial statements and accompanying notes. Actual results could differ from those estimates.

On an ongoing basis, the Company evaluates its estimates and assumptions, including those related to revenue recognition, the useful lives of property and equipment, the recoverability of long-lived assets, the incremental borrowing rate for leases, and assumptions used for purposes of determining stock-based compensation, income taxes, the fair value of investments and the fair value of the derivative and warrant liability and discount and rebate liabilities, among others. The Company bases its estimates on historical experience and on various other assumptions that it believes to be reasonable, the results of which form the basis for making judgments about the carrying value of assets and liabilities.

Investments

The Company maintains investment securities that are classified as available-for-sale securities for which the Company has elected the fair value option under ASC 825, Financial Instruments("ASC 825"). As such, these securities are carried at fair value with unrealized gains and losses included in fair value adjustment related to investments on the unaudited condensed consolidated statements of operations. The securities primarily consist of U.S.U.S. Treasury securities and U.S. government-sponsored agency securities and are included in securities at fair value in the unaudited condensed consolidated balance sheets. As of March 31, 2024, 31,2023,and December 31, 2022,2023, the Company held securities with an aggregate fair value of $34.4 million$9.9 million and $16.9 $24.7million, respectively, that contained aggregate unrealized losses of(losses) gainsof approximately $0.4($0.1) million and $0.6$0.2 million, respectively. Applying fair value accounting to these debt securities more accurately represents the Company's investment strategy due to the fact that excess cash is currently being invested for the purpose of funding future operations. In addition, the Company holds certificates of deposit totaling $20.7 million as of March 31,2023, and December 31, 2022, and are included in short-term investments - other in the unaudited condensed consolidated balance sheets. Interest income is recognized as earned using an effective yield method giving effect to the amortization of premium and accretion of discount and is based on thethe economic life of the securities. Interest income is included in Interestinterest and other income, net in the unaudited condensed consolidated statements of operations.

Variable Interest Entities

The primary beneficiary of a variable interest entity ("VIE") is required to consolidate the assets and liabilities of the VIE. When the Company obtains a variable interest in another entity, it assesses at the inception of the relationship and upon occurrence of certain significant events whether the entity is a VIE, and if so, whether the Company is the primary beneficiary of the VIE based on its power to direct the activities of the VIE that most significantly impact the VIE's economic performance and the Company's obligation to absorb losses or the rights to receive benefits from the VIE that could potentially be significant to the VIE.

To assess whether the Company has the power to direct the activities of the VIE that most significantly impact the VIE's economic performance, the Company considers all the facts and circumstances, including the Company's role in establishing the VIE and the Company's ongoing rights and responsibilities. The assessment includes identifying the activities that most significantly impact the VIE's economic performance and identifying which party, if any, has the power to direct those activities. In general, the parties that make the most significant decisions affecting the VIE (management and representation on the Board of Directors) are deemed to have the power to direct the activities of a VIE.

To assess whether the Company has the obligation to absorb losses of the VIE or the rights to receive benefits from the VIE that could potentially be significant to the VIE, the Company considers all of its economic interests that are deemed to be variable interests in the VIE.

This assessment requires judgement in determining whether these interests, in the aggregate, are considered potentially significant to the VIE. As of March 31, 2024, and December 31, 2023, the Company identified Acer to be the Company's sole interest in a VIE (Note L). As Zevra is the final decision maker for all of Acer's research, development, and commercialization of drug candidates that it is producing, the Company directs the activities of Acer that most significantly impact its performance. Therefore, the Company is the primary beneficiary of this VIE for accounting purposes. 

The Company recognizes revenue in accordance with the provisions of ASC 606, Revenue from Contracts with Customers (“ASC 606”) and, as a result, follows the five-step model when recognizing revenue: 1) identifying a contract; 2) identifying the performance obligations; 3) determining the transaction price; 4) allocating the price to performance obligations; and 5) recognizing revenue when the performance obligations have been fulfilled.

Arimoclomol Early Access Program

Net revenue includes revenue from the sale of arimoclomol for the treatment of NPC under the remunerated early access compassionate use program in France (“French nATU”). An early access compassionate use program is a program giving specific patients access to a drug, which is not yet approved for commercial sale. Only drugs targeting serious or rare indications and for which there is currently no appropriate treatment are considered for early access compassionate use programs. Further, to be considered for the early access compassionate use program, the drug must have proven efficacy and safety and must either be undergoing price negotiations or seeking marketing approval. In accordance with ASC 606, the Company recognizes revenue when fulfilling its performance obligation under the Arimoclomol Early Access Program ("Arimoclomol EAP") by transferring control of promised goods or services to its customer, in an amount that reflects the consideration that the Company expects to receive in exchange for those goods or services. In determining when the customer obtains control of the product, the Company considers certain indicators, including whether the Company has a present right to payment from the customer, whether title and/or significant risks and rewards of ownership have transferred to the customer and whether the customer acceptance has been received. Revenue is recognized net of sales deductions, including discounts, rebates, applicable distributor fees, and revenue-based taxes. Under the French nATU, the manufacturer can set its own price for the drug products until a price agreement with the authorities is in place. Any excess in the price charged the manufacturer compared to the price agreed with the health authorities once the drug product is approved in France must be repaid. The repayment is considered in the clawback liability (rebate). An estimate of net revenue and clawback liability are recognized using the ‘expected value’ method. Accounting for net revenue and clawback liability requires determination of the most appropriate method for the expected final transaction price, which depends on the terms and conditions in the contracts with the French Health Authorities and is subject to price negotiations with the French Health Authorities, following marketing approval. This estimate also requires assumptions with respect to inputs into the method, including current pricing of comparable marketed products within the rare disease area in France. Management has considered the expected final sales price as well as the price of similar drug products. The Company is operating within a rare disease therapeutic area where there is unmet treatment need and hence a limited number of comparable commercialized drugs products. The limited available relevant market information for directly comparable commercialized drugs within rare disease increases the uncertainty in management's estimate. For the three months ended March 31, 2023, the Company recognized revenue related to the Arimoclomol EAP in France of $2.0million, which is net of a clawback liability of $1.3 million and other gross to net adjustments. As part of the Arimoclomol Purchase Agreement the Company assumed an estimated reserve liability of $5.2 million related to revenue generated from the Arimoclomol EAP in France. The total estimate reserve liability as of March 31,2023, including the additional clawback liability for the three months ended March 31,2023, was $10.5million. The total reserve liability as of December 31, 2022, was $9.0 million. As of March 31, 2023, and December 31, 2022, this estimated reserve liability is recorded as discount and rebate liabilities in the unaudited condensed consolidated balance sheets and is separated into current and long-term based upon the timing of the expected payment to the French regulators.

Licensing Agreements

The Company enters into licensing agreements with licensees that fall under the scope of ASC 606.

The terms of the Company’s licensing agreements typically include one or more of the following: (i) upfront fees; (ii) milestone payments related to the achievement of development, regulatory, or commercial goals; and (iii) royalties on net sales of licensed products. Each of these payments may result in licensing revenues.

As part of the accounting for these agreements, the Company must develop estimates and assumptions that require judgment to determine the underlying stand-alone selling price for each performance obligation which determines how the transaction price is allocated among the performance obligations. Generally, the estimation of the stand-alone selling price may include such estimates as independent evidence of market price, forecasted revenues or costs, development timelines, discount rates, and probability of regulatory success. The Company evaluates each performance obligation to determine if they can be satisfied at a point in time or over time, and it measures the services delivered to the licensee which are periodically reviewed based on the progress of the related program. The effect of any change made to an estimated input component and, therefore revenue or expense recognized, would be recorded as a change in estimate. In addition, variable consideration (e.g., milestone payments) must be evaluated to determine if it is constrained and, therefore, excluded from the transaction price.

Up-front Fees: If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from the transaction price allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time.

Milestone Payments: At the inception of each arrangement that includes milestone payments (variable consideration), the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s or the licensee’s control, such as non-operational developmental and regulatory approvals, are generally not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of milestones that are within its or the licensee’s control, such as operational developmental milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration revenues and earnings in the period of adjustment. Revisions to the Company’s estimate of the transaction price may also result in negative licensing revenues and earnings in the period of adjustment.

Product Revenues, Net

Net revenues from product sales is recognized at the transaction price when the customer obtains control of the Company's products, which occurs at a point in time, typically upon receipt of the product by the customer.

The Company's net revenues represent total revenues adjusted for discounts and allowances, including estimated cash discounts, chargebacks, rebates, returns, copay assistance, data fees and wholesaler fees for services. These adjustments represent variable consideration under ASC 606 and are recorded as a reduction of revenue. These adjustments are established by management as its best estimate based on available information and will be adjusted to reflect known changes in the factors that impact such allowances. Adjustments for variable consideration are determined based on the contractual terms with customers, historical trends, communications with customers and the levels of inventory remining in the distribution channel, as well as expectations about the market for the product and anticipated introduction of competitive products.

AZSTARYS License AgreementInventories

In September 2019, The value of inventory is recorded at its net realizable value. The Company determines the Company entered into a Collaboration and License Agreement (the “AZSTARYS License Agreement”) with Commave Therapeutics SA ("Commave"), an affiliatecost of Gurnet Point Capital ("GPC"). Under the AZSTARYS License Agreement, the Company granted to Commave an exclusive, worldwide license to develop, manufacture and commercialize the Company’s product candidates containing SDX and d-MPH, including AZSTARYS, or anyits other product candidates containing SDX and developed to treat ADHD or any other central nervous system ("CNS") disease. Corium, Inc. ("Corium") was tasked by Commave, to lead all commercialization activities for AZSTARYS under the AZSTARYS License Agreement. Pursuant to the AZSTARYS License Agreement, Commave agreed to pay milestone payments upon the occurrence of specified regulatory milestonesinventories, which includes amounts related to AZSTARYS, additional fixed payments upon the achievement of specified U.S. sales milestones,materials and quarterly, tiered royalty payments basedmanufacturing overhead, on a range of percentages of net sales. Commave is obligated to make such royalty payments on a product-by-product basis until expiration of the royalty term for the applicable product.

In April 2021, firstthe Company entered into Amendment-in, No.first1 to the AZSTARYS License Agreement (the "AZSTARYS Amendment"). Pursuant to the AZSTARYS Amendment, the Company and Commave agreed to modify the compensation terms of the AZSTARYS License Agreement. The AZSTARYS Amendment increased the total remaining future regulatory and sales milestone payments related to AZSTARYS to up to an aggregate of $590.0 million in payments upon the occurrence of specified regulatory milestones related to AZSTARYS and upon the achievement of specified U.S. net sales milestones.

Commave also agreed to be responsible for and reimburse the Company for all of the development, commercialization and regulatory expenses incurred on the licensed products, subject to certain limitations as set forth in the AZSTARYS License Agreement. As part of this agreement, the Company is obligated to perform consulting services on behalf of Commave related to the licensed products. For these consulting services, Commave has agreed to pay the Company a set rate per hour on any consulting services performed on behalf of Commave for the benefit of the licensed products.

In accordance with the terms of the Company’s March 20,2012 Termination Agreement with Aquestive Therapeutics, Aquestive Therapeutics has the right to receive an amount equal to 10% of any royalty or milestone payments made to the Company related to AZSTARYS, KP879 or KP1077 under the AZSTARYS License Agreement.-out basis.

The AZSTARYS License Agreement is withinCompany may scale-up and make commercial quantities of its product candidates prior to the scopedate it anticipates that such product will receive final regulatory approval. The scale-up and commercial production of ASCpre-launch inventory involves the risk that such products 606,may  as the transaction represents a contract with a customer where the participants function in a customer / vendor relationship and are not exposed equallybe approved for marketing on a timely basis, or ever. This risk notwithstanding, the Company may scale-up and build pre-launch inventory of product that have not received final regulatory approval when the Company believes such action is appropriate in relation to the risks and rewardscommercial value of the activities contemplated underproduct launch opportunity. Inventory manufactured prior to regulatory approval is recorded as research and development expense until regulatory approval for the AZSTARYS License Agreement. Usingproduct is obtained. Inventory used in clinical trials is also expensed as research and development expense, when selected for such use. Inventory that can be used in either the conceptsproduction of ASC 606, the Company identified the grant of the exclusive, worldwide license and the performance of consulting services, which includes the reimbursement of out-of-pocket third-partyclinical or commercial products is expensed as research and development costs as its onlywhen identified for use in a clinical manufacturing campaign. The cost of finished goods inventory that is shipped to a customer to support the Company’s patient assistance programs is expensed when those shipments take place. As of twoMarch 31, 2024,  performance obligations at inception. Theand December 31, 2023, the Company further determineddid not have pre-launch inventory that the transaction price, at inception, under the agreement was $10.0 million upfront payment plus the fair value of the Development Costs (as defined in the AZSTARYS License Agreement) which was allocated among the performance obligations based on their respective related stand-alone selling price.qualified for capitalization.

The Company is entitled to additional payments from Commave conditioned uponperforms an assessment of the achievementrecoverability of specified regulatory milestones related to AZSTARYS and the achievement of certain U.S. sales milestones. Further, Commave will pay the Company quarterly, tiered royalty payments based on a range of percentage of Net Sales (as defined in the AZSTARYS License Agreement). The Company concluded that these regulatory milestones, sales milestones and royalty payments each contain a significant uncertainty associated with a future event. As such, these milestone and royalty payments are constrained at contract inception and are not included in the transaction price as the Company could not conclude that it is probable a significant reversal in the amount of cumulative revenue recognized will not occur surrounding these milestone payments. At the end ofcapitalized inventory during each reporting period and writes down any excess and obsolete inventory to its net realizable value in the period in which the impairment is first identified. Such impairment charges, should they occur, are recorded as a component of cost of product sales in the statements of operations and comprehensive loss. The determination of whether inventory costs will be realizable requires the use of estimates by management. If actual market conditions are less favorable than projected by management, additional write-downs of inventory may be required. Additionally, the Company’s product is subject to strict quality control and monitoring that it performs throughout the manufacturing process. In the event that certain batches or units of product do not meet quality specifications, the Company updateswill record a charge to cost of product sales, to write-down any unmarketable inventory to its assessment of whether the milestone and royalty payments are constrained by considering both the likelihood and magnitude of the potential revenue reversal. For the three months ended March 31, 2023 and 2022, the Company recognized $0.6 million and $0.1 million of revenue under the AZSTARYS License Agreement, respectively. There was no deferred revenue related to this agreement as of March 31, 2023, or December 31, 2022.

Consulting Arrangements

The Company enters into consulting arrangements with third parties that fall under the scope of ASC 606.  These arrangements may require the Company to deliver various rights, services, including research and development services, regulatory services and/or commercialization support services. The underlying terms of these arrangements generally provide for consideration to the Company in the form of consulting fees and reimbursements of out-of-pocket third-party research and development, regulatory and commercial costs.

Corium Consulting Agreement

In July 2020, the Company entered into a consultation services arrangement (the “Corium Consulting Agreement”) with Corium under which Corium engaged the Company to guide the product development and regulatory activities for certain current and potential future products in Corium’s portfolio, as well as continue supporting preparation for the potential commercial launch of AZSTARYS (together, “Corium Consulting Services”). Corium is a portfolio company of GPC and was tasked by Commave to lead all commercialization activities for AZSTARYS under the AZSTARYS License Agreement, as discussed above.

Under the Corium Consulting Agreement, the Company was entitled to receive payments from Corium of up to $15.6 million, $13.6 million of which was paid in quarterly installments through March 31,2022. The remaining $2.0 million was conditioned upon the approval by the FDA of the NDA for Corium's product candidate, ADLARITY. This $2.0 million was earned in the first quarter of 2022. Corium also agreed to be responsible for and reimburse the Company for all development, commercialization and regulatory expenses incurred as part of the performance of the Corium Consulting Services. The Corium Consulting Agreement is within the scope of ASC 606, as the transaction represents a contract with a customer where the participants function in a customer / vendor relationship and are not exposed equally to the risks and rewards of the activities contemplated under the Corium Consulting Agreement. The Company identified the performance of consulting services, which includes the reimbursement to the Company of third-party pass-through costs, as its only performance obligation at inception. The Company further determined that the transaction price, at inception, under the agreement was $13.6 million which is the fair value of the consulting services, including the reimbursement of third-party pass-through costs. The Company concluded that the regulatory milestone contains a significant uncertainty associated with a future event. As such, this milestone is constrained at contract inception and is not included in the transaction price as the Company could not conclude that it is probable a significant reversal in the amount of cumulative revenue recognized will not occur surrounding these milestone payments. 

The Company determined that the performance of consulting services, including reimbursement of third-party pass-through costs, is a performance obligation that is satisfied over time as the services are performed and the reimbursable costs are paid. As such, the revenue related to the performance obligation was recognized as the consulting services were performed and the services associated with the reimbursable third-party pass-through costs were incurred and paid by the Company, in accordance with the practical expedient allowed under ASC 606 regarding an entity’s right to consideration from a customer in an amount that corresponds directly to the value to the customer of the entity’s performance completed to date. 

For the three months ended March 31, 2023, and 2022, the Company recognized $0.2 million and $3.5 million of revenue, respectively, under the Corium Consulting Agreement. As of March 31, 2023, and December 31, 2022, the Company had no deferred revenue related to this agreement. The Corium Consulting Agreement expired on March 31, 2023.estimated net realizable value. 

Foreign currency

Assets and liabilities are translated into the reporting currency using the exchange rates in effect on the unaudited consolidated condensed balance sheet dates. Equity accounts are translated at historical rates, except for the change in retained earnings during the year, which is the result of the income statement translation process. Revenue and expense accounts are translated using the weighted average exchange rate during the period. The cumulative translation adjustments associated with the net assets of foreign subsidiaries are recorded in accumulated other comprehensive income/loss in the accompanying unaudited condensed consolidated statements of stockholders’ equity.

Warrants

The Company accounts for warrants as either equity-classified or liability-classified instruments based on an assessment of the warrant’s specific terms and applicable authoritative guidance in FASB ASC Topic 480, Distinguishing Liabilities from Equity (ASC 480) and FASB ASC Topic 815, Derivatives and Hedging (ASC 815). The assessment considers whether the warrants are freestanding financial instruments pursuant to ASC 480, meet the definition of a liability pursuant to ASC 480, and whether the warrants meet all of the requirements for equity classification under ASC 815, including whether the warrants are indexed to our own stock and whether the warrant holders could potentially require “net cash settlement” in a circumstance outside of the company’s control, among other conditions for equity classification. This assessment, which requires the use of professional judgment, is conducted at the time of warrant issuance and as of each subsequent quarterly period end date while the warrants are outstanding.

For warrants that meet all criteria for equity classification, the warrants are required to be recorded as a component of additional paid-in capital, on the unaudited condensed consolidated statement of stockholders’ deficit at the time of issuance. For warrants that do not meet all the criteria for equity classification, the warrants are required to be recorded at their initial fair value on the date of issuance, and on each balance sheet date thereafter. Changes in the estimated fair value of the warrants are recognized as a non-cash gain or loss in other expense, net, on the unaudited condensed consolidated statement of operations. The fair value of the warrants was estimated using the Black-Scholes option pricing model.

New Accounting Pronouncements Not Yet Adopted

Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures

In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which modifies the disclosure and presentation requirements of reportable segments. The amendments in the update require the disclosure of significant segment expenses that are regularly provided to the chief operating decision maker ("CODM") and included within each reported measure of segment profit and loss. The amendments also require disclosure of all other segment items by reportable segment and a description of its composition. Additionally, the amendments require disclosure of the title and position of the CODM and an explanation of how the CODM uses the reported measure(s) of segment profit or loss in assessing segment performance and deciding how to allocate resources. This update is effective for annual periods beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. The Company is currently evaluating the impact that this guidance will have on the presentation of its consolidated financial statements and accompanying notes.

Income Taxes (Topic 740): Improvements to Income Tax Disclosures

Secured Promissory Note

In connection with the Merger (Note L), on August 30, 2023, the Company and Nantahala, entered into a secured promissory note payable by Zevra to Nantahala in the original principal amount of $5.0 million (the "Nantahala Note"). The Nantahala Note initially bore interest at 9.0% per annum, payable quarterly in arrears in cash. The interest rate increased to 12.0% per annum effective March 1, 2024, as the Nantahala Note remained unpaid six months from its issue date. The additional 3.0% interest would have been paid in shares of Zevra's common stock based on the volume weighted average trading price ("VWAP") of Zevra's common stock during the twenty consecutive trading days ending on the date before such interest payment date. Beginning on the first interest payment date following the second anniversary of the Nantahala Note, and on each interest payment date thereafter, Zevra was required to make $0.6 million amortization payments on the Nantahala Note until it was paid in full. All principal and unpaid interest on the Nantahala Note would have been due on August 30, 2026, the third anniversary of the Nantahala Note. Zevra was entitled to prepay the Nantahala Note at any time without penalty. The Nantahala Note was secured by Zevra’s interest in (i) the loan assets under the Loan Purchase Agreement described in Note L; (ii) the note assets under the Note Purchase Agreement described in Note L; (iii) the Bridge Loan described in Note L; and (iv) the proceeds therefrom. The Company used the proceeds from the Nantahala Note, along with $12.0 million in cash and 98,683 shares of Zevra's common stock, to acquire Acer's term loans, as more fully described in Note L. In April 2024, the Nantahala Note was repaid in full and terminated. At the time of repayment, Nantahala elected to receive a cash payment in lieu of shares of Zevra's common stock in exchange for the additional 3.0% interest accrued for the period from March 1, 2024, through April 5, 2024. The outstanding balance under the Nantahala Note is included in long-term liabilities as of March 31, 2024, as it was refinanced with long-term debt after the balance sheet date, but prior to issuance of the unaudited condensed consolidated financial statements.

As of March 31, 2024, and December 31, 2023, the Company had a secured promissory note outstanding, in the aggregate principal amount, as follows (in thousands):

Future minimum principal payments under the secured promissory note as of March 31, 2024, were as follows (in thousands):

Line of Credit

On January 26, 2023, the Company and Wells Fargo, as lender, entered into a revolving margin account agreement. The Company's investments are used as collateral for the loan and the amount the Company is able to borrow is limited to 80-90% of its outstanding investment balance held with Wells Fargo. The margin account bore interest at the Prime rate minus 225 basis-points. As of March 31, 2024, and December 31, 2023, $37.9 million and $37.7 million was outstanding under the margin account, respectively. In April 2024, the Company repaid the outstanding balance under the margin account with Wells Fargo, and upon such repayment, the margin capabilities were removed from the account. The outstanding balance under the margin account is included in long-term liabilities as of March 31, 2024, as it was refinanced with long-term debt after the balance sheet date, but prior to issuance of the unaudited condensed consolidated financial statements. As of March 31, 2024, the remaining borrowing capacity under the margin account was approximately $3.8 million. 

Term Loans

As a subsequent event, on April 5, 2024 (the "Term Loans Closing Date"), the Company entered into a credit agreement (the “Credit Agreement”) with HCR Stafford Fund II, L.P., HCR Potomac Fund II, L.P., and Perceptive Credit Holdings IV, LP (collectively, the “Lenders”), and Alter Domus (US) LLC, as administrative agent (the “Administrative Agent”).

Under the terms of the Credit Agreement, the Lenders provided a senior secured loan facility to the Company in the aggregate principal amount of $100.0 million, which is divided into three tranches as follows: (i) $60.0 million which was funded in full on the Term Loans Closing Date; (ii) $20.0 million which is available to the Company in up to two drawings, each in an amount not to exceed $10.0 million, at the Company’s option until 18 months following the Term Loans Closing Date; and (iii) $20.0 million which is available to the Company upon approval by the FDA of the NDA for arimoclomol for the treatment of NPC, at the Company’s option until December 31, 2024 (collectively, the “Term Loans”). 

The principal amount of the Term Loans outstanding (the “Outstanding Principal Amount”) will bear interest at a rate equal to 3-Month Term SOFR plus 7.00% per annum. If the net product sales for the calendar year ending December 31, 2025, exceed $100.0 million, the Outstanding Principal Amount will bear interest at 3-Month Term SOFR plus 6.00% per annum. If the net product sales for the calendar year ending December 31, 2025, do not exceed $100.0 million, then for any subsequent period of four consecutive fiscal quarters ending on or after March 31, 2026, in which net product sales exceed $125.0 million, the Outstanding Principal Amount will bear interest at 3-Month Term SOFR plus 6.50% per annum. In all cases, the 3-Month Term SOFR rate will be subject to a floor of 4.00% per annum. Interest will be payable quarterly in arrears on the last day of each calendar quarter. The Company has the option to pay up to 25% of the interest in-kind beginning on the Term Loans Closing Date, through and including March 31, 2026. The Term Loans will mature on the fifth anniversary of the Term Loans Closing Date. In connection with the Credit Agreement, the Company incurred approximately $1.7 million of costs, which primarily consisted of underwriting, legal and other professional fees, and is included in other long-term assets in the unaudited condensed consolidated balance sheet as of March 31, 2024.

The Credit Agreement contains customary affirmative and negative covenants by the Company, which among other things, will require the Company to provide certain financial reports to the Lenders, meet certain minimum net product sales amounts, and limit the ability of the Company to incur or guarantee additional indebtedness, engage in certain transactions, and effect a consolidation or merger, without consent. The obligations of the Company under the Credit Agreement may be accelerated upon customary events of default, including non-payment of principal, interest, fees and other amounts, covenant defaults, insolvency, material judgments, or inaccuracy of representations and warranties The Term Loans are secured by a first priority perfected lien on, and security interest in, substantially all current and future assets of the Company. The proceeds of the Term Loans shall be used to refinance certain existing indebtedness of the Company and its subsidiaries. The Company will use the remaining proceeds to pay fees and expenses related to the Debt Financing and fund the development and commercialization of OLPRUVA and arimoclomol.

The AZSTARYS License Agreement is within the scope of ASC 606, as the transaction represents a contract with a customer where the participants function in a customer / vendor relationship and are not exposed equally to the risks and rewards of the activities contemplated under the AZSTARYS License Agreement.

The Company concluded that these regulatory milestones, sales milestones and royalty payments each contain a significant uncertainty associated with a future event. As such, these milestone and royalty payments are constrained at contract inception and are not included in the transaction price as the Company could not conclude that it is probable a significant reversal in the amount of cumulative revenue recognized will not occur surrounding these milestone payments. At the end of each reporting period, the Company updates its assessment of whether the milestone and royalty payments are constrained by considering both the likelihood and magnitude of the potential revenue reversal. For the three months ended March 31, 2024, and 2023, the Company recognized $1.2 million and $0.6 million of revenue under the AZSTARYS License Agreement., respectively, primarily related to royalties. There was no deferred revenue related to this agreement as of March 31,2024, or December 31, 2023.

Product Revenues, Net

Arimoclomol Expanded Access Program

Net revenue includes revenue from the sale of arimoclomol for the treatment of NPC under the remunerated expanded access compassionate use program in France (“French nATU”). An expanded access compassionate use program is a program giving specific patients access to a drug, which is not yet approved for commercial sale. Only drugs targeting serious or rare indications and for which there is currently no appropriate treatment are considered for expanded access compassionate use programs. Further, to be considered for the expanded access compassionate use program, the drug must have proven efficacy and safety and must either be undergoing price negotiations or seeking marketing approval.

In accordance with ASC 606, the Company recognizes revenue when fulfilling its performance obligation under the Arimoclomol Expanded Access Program ("Arimoclomol EAP") by transferring control of promised goods or services to its customer, in an amount that reflects the consideration that the Company expects to receive in exchange for those goods or services. In determining when the customer obtains control of the product, the Company considers certain indicators, including whether the Company has a present right to payment from the customer, whether title and/or significant risks and rewards of ownership have transferred to the customer and whether the customer acceptance has been received. Revenue is recognized net of sales deductions, including discounts, rebates, applicable distributor fees, and revenue-based taxes.

OLPRUVA Product Sales

On December 27, 2022, the FDA approved OLPRUVA (sodium phenylbutyrate), a prescription medicine used along with certain therapy, including changes in diet, for the long-term management of adults and children with UCDs weighing 44 pounds (20 kg) or greater and with a body surface area of 1.2m2 or greater. On November 17, 2023, the Company acquired OLPRUVA in connection with the Merger (Note L). To commercialize OLPRUVA for oral suspension in the U.S. the Company is building marketing, sales, medical affairs, distribution, managerial and other non-technical capabilities or making arrangements with third parties to perform these services. The Company's current distributor for sales of OLPRUVA is a single specialty pharmacy provider. However, the Company intends to establish additional distributors such as other retail pharmacies and certain medical centers or hospitals. In addition to distribution agreements, the Company enters into arrangements with health care providers and payors that provide for government mandated and/or privately negotiated rebates with respect to the purchase of its products.

For the three months ended March 31, 2024, and 2023, sales of OLPRUVA were de minimis due to limited shipments to our specialty pharmacy in Q12024.

Accounts and Other Receivables

Accounts and other receivables consist of receivables from product sales, receivables under the AZSTARYS License Agreement and Arimoclomol EAP, as well as receivables related to consulting arrangements, income tax receivables and other receivables due to the Company. Receivables under the AZSTARYS License Agreement are recorded for amounts due to the Company related to reimbursable third-party costs and royalties on product sales. Receivables under the Arimoclomol EAP are recorded for product sales under the French nATU. These receivables as well as the receivables related to consulting arrangements, are evaluated to determine if any reserve or allowance should be established at each reporting date. As of March 31, 2023,2024, the Company had receivables related to the Arimoclomol EAP of $5.3 million, $4.8 million, AZSTARYS License Agreement of $0.6 million, consulting arrangements of $0.2 m1.2 miillion,llion, income tax receivables of $1.0 $0.1 million and other receivables of $0.7 million. $2.2 million. As of December 31, 2022,2023, the Company had receivables related to the Arimoclomol EAP of $6.3 million, Corium Consulting Agreement of $4.7$0.2 m miillion,llion, AZSTARYS License Agreement of $0.5 million, income tax receivables of $0.9 million $11.4 million, and other receivables of $0.4$1.3 million. As of March 31, 2023, 2024,and December 31, 2022,2023, no reserve or allowance for doubtful accounts had been established.

Line of Credit

On May 31,2022, the Company and Ameris Bank, as lender, entered into a $20.0 million revolving loan agreement (the “Line of Credit”). Proceeds of the revolving facility provided by the Line of Credit are to be used for general corporate purposes. Loans under the Line of Credit bear interest at the Secured Overnight Financing Rate ("SOFR") plus 1.60%, with a SOFR floor of 0.00%.

The revolving facility under the Line of Credit is secured by a perfected security interest in deposit accounts. The revolving facility under the Line of Credit is subject to customary affirmative and negative covenants.

The latest maturity date of the loans under the Line of Credit was May 31,2025. The Line of Credit contained customary events of default that could have led to an acceleration of the loans, including cross-default, bankruptcy and payment defaults. As of December 31, 2022, the Company had drawn $12.8 million from the Line of Credit to finance the transactions under the Arimoclomol Purchase Agreement, and this amount was supported by a $12.8 million certificate of deposit which was shown as long-term investments - others in the unaudited condensed consolidated balance sheet as of December 31, 2022. The remaining $7.2 million under the Line of Credit was in a separate interest-bearing certificate of deposit and is also recorded as long-term investments - other in the unaudited condensed consolidated balance sheets as of December 31, 2022. These certificates of deposit are pledged as collateral against the Line of Credit and could not be redeemed so long as the $20.0 million remained available under the Line of Credit. The total value of the certificates of deposit held with Ameris Bank must meet or exceed the amount available to borrow under the Line of Credit so long as the Line of Credit remains active. On January 31, 2023, the Company repaid the $12.8 million outstanding under the Line of Credit in full and closed the Line of Credit. In conjunction with closing the Line of Credit, the maturity dates of the certificates of deposit were modified to May 2023. As such, the certificates of deposit are classified as short-term investments - other in the unaudited condensed consolidated balance sheet as of March 31, 2023. No amounts are outstanding under the Line of Credit as of March 31, 2023.

On January 26, 2023, the Company and Wells Fargo, as lender, entered into a revolving margin account agreement under which the Company initially borrowed $12.8 million. The Company's investments are used as collateral for the loan and the amount the Company is able to borrow is limited to 80-90% of its outstanding investment balance held with Wells Fargo. The margin account bears interest at the Prime rate minus 225 basis-points. As of March 31, 2023, $12.9 million was outstanding under the margin account.

From time to time, the Company is involved in various legal proceedings arising in the normal course of business. For some matters, a liability is not probable, or the amount cannot be reasonably estimated and, therefore, an accrual has not been made. However, for such matters when it is probable that the Company has incurred a liability and can reasonably estimate the amount, the Company accrues and discloses such estimates.

DuringStockholder Litigation Related to the Merger

On firstOctober 12, 2023, Brodsky & Smith, purporting to act as counsel for Jerry Beavee, who was asserted to be a stockholder of Acer, filed a complaint entitled Jerry Beavee v. Acer Therapeutics Inc., et al., No. quarter1:23-cv-08995 in the United States District Court for the Southern District of New York (the "Action") alleging that defendants violated Section 2023,14 the Company(a) and KVK-Tech, Inc. ("KVK") began discussing a possible termination20(a) of the Collaboration and License Agreement (the “Agreement”)Securities Exchange Act of 1934 by filing the Preliminary Merger Registration Statement which allegedly omitted certain information that the parties entered into onsuch counsel asserts is material to Acer’s required disclosure. On October 25, 2018.30, 2023, UnderAcer filed with the termsSEC a Schedule DEF14A that contained additional information regarding the Merger, which mooted the disclosure claims alleged in the Action. On December 8, 2023, Jerry Beavee filed with the court a notice of dismissal of the Agreement, each party has groundsAction without prejudice.

On October 20, 2023, Long Law, LLC and Acocelli Law, PLLC, purporting to terminate the Agreement. While negotiations are on-going, inact as counsel for Kevin Turner, who was asserted to be a stockholder of Acer, filed a complaint entitled Kevin Turner v. Acer Therapeutics Inc., et al., April 2023, No.the Company determined that is probable that the Agreement will be terminated and accrued an estimated settlement to KVK of $0.9 million, which is included in research and development1:23-cv-01185 in the unaudited condensed consolidated statement of operationsUnited States District Court for the District of Delaware alleging that defendants violated Section three14(a) and 20(a) of the Securities Exchange Act of 1934 months endedas well as SEC Rule 14a-9 by filing the Definitive Proxy Statement which allegedly omitted certain information that such counsel asserts is material to Acer’s required disclosure. The complaint prays that, if asserted omissions are not adequately corrected, then Turner will seek to enjoin Acer from holding a stockholder meeting to approve the Merger and, if the Merger closes, will seek to rescind it and seek an award of damages.

On October 20, 2023, Long Law, LLC, purporting to act as counsel for Matthew Jones, who was asserted to be a stockholder of Acer, filed a complaint entitled Matthew Jones v. Acer Therapeutics Inc., et al., No.1:23-cv-01186 in the United States District Court for the District of Delaware alleging that defendants violated Section 14(a) and 20(a) of the Securities Exchange Act of 1934 as well as SEC Rule 14a-9 by filing the Definitive Proxy Statement which allegedly omitted certain information that such counsel asserts is material to the Acer’s required disclosure. The complaint prays that, if asserted omissions are not adequately corrected, then Jones will seek to enjoin Acer from holding a stockholder meeting to approve the Merger and, if the Merger closes, will seek to rescind it and seek an award of damages.

As of March 31, 2023.2024, As ofand December 31, 20222023, no accruals have been made related to commitments and contingencies. The Company intends to vigorously defend these lawsuits and believes that it has meritorious defenses to each. However, litigation is inherently uncertain, and any judgment or injunctive relief entered against the Company or any adverse settlement could adversely affect the Company’s business, results of operations and financial condition.

Authorized, Issued, and Outstanding Common Shares

As of March 31, 20232024, and December 31, 20222023, the Company had authorized shares of common stock of 250,000,000 shares. Of the authorized shares, 35,457,49643,426,186 and 3543,110,360 share,450,257 sharess of common stock were issued as of March 31, 2023, 2024,and December 31, 2022,2023, respectively, andan 33,881,804 and 34,540,304 respectively shares41,850,494 and 41,534,668 shares of common stock were outstanding as of March 31, 20232024, and December 31, 20222023, respectively.

As of March 31, 20232024 and December 31, 20222023, the Company had reserved authorized shares of common stock for future issuance as follows:

Common Stock Activity

The following table summarizes common stock activity for the three months ended March 31, 20232024:

Authorized, Issued, and Outstanding Preferred Stock

As of March 31, 2023,2024, and December 31, 2022,2023, the Company had 10,000,000 shares of authorized preferred stock, none of which were designated, issued, or outstanding.    

Warrants to Purchase Common Stock

Warrants to Purchase Common Stock

In June 2014, the Company entered into a multi-tranche credit facility (the "Deerfield Facility Agreement") with Deerfield Private Design Fund III, LP (“Deerfield”). The Company has issued to Deerfield a warrantwarrants to purchase 120,192 shares of the Company's common stock to various third parties, of which is exercisable at $38.34 per share until June 2,2024, and Deerfield assigned this warrant to OTA LLC in December 5,603,729 remain outstanding as of 2022March 31, 2024, (the “OTA Warrant”). This warrant qualifiesand are immediately exercisable. These warrants qualify as a participating securitysecurities under ASC Topic 260, Earnings per Share, and isare treated as such in the net loss per share calculation (Note H). If a Major Transaction occurs (as defined in the Deerfield Facility Agreement), OTAThe Company may require the Companybe required to redeem the OTA Warrantthese warrants for a cash amount equal to the Black-Scholes value of the portion of the OTA Warrantwarrants to be redeemed (the “Warrant Put“Put Option”). 

In connection with the Merger (Note L), in November 2023, the Company directly issued to certain investors an aggregate of 1,382,489 shares of its common stock, par value $0.0001 per share, and accompanying warrants to purchase up to 1,382,489 shares of its common stock (the "2023 Warrants") at a combined offering price of $4.34 per share of common stock and the Warrants and an aggregate of 917,934 shares of its common stock in exchange for the cancellation of a warrant to purchase 2,920,306 shares of common stock of Acer. The Warrants are immediately exercisable and expire on November 22, 2028. The Company used the net proceeds of approximately $6.0 million from the offering for general corporate purposes. These warrants are separately exercisable by the warrant holders. While the warrants are outstanding (but unexercised), the warrant holders will participate in any dividend or other distribution of the Company’s assets to its common stockholders by way of return of capital or otherwise. As of March 31, 2024, and December 31, 2023, none of the warrants have been exercised. The warrants have been evaluated to determine the appropriate accounting and classification pursuant to ASC Topic 480, Distinguishing Liabilities from Equity, and ASC Topic 815, Derivatives and Hedging. Generally, freestanding warrants should be classified as (i) liabilities if the warrant terms allow settlement of the warrant exercise in cash and (ii) equity if the warrant terms only allow settlement in shares of common stock. 

The Company determined that its outstanding warrants and the OTA WarrantPut Option should be recorded as a liability and stated at fair value at each reporting period. Changes to the fair value of the warrant liability are recorded through the unaudited condensed consolidated statements of operations as a fair value adjustment (Note G).

The Company issuedrelated to KVK a warrant to purchase up to 31,250 shares of common stock of the Company at an exercise price of $36.80 per share (the “KVK Warrant”). The KVK Warrant is initially not exercisable for any shares of common stock. Upon the achievement of eachand CVR liability. As of fourMarch 31, 2024,  specified milestones under the KVK Warrant, the KVK Warrant will become exercisable. The exercise price and the number and type of shares underlying the KVK Warrant are subject to adjustment in the event of specified events, including a reclassification of the Company’s common stock, a subdivision or combination of the Company’s common stock, or in the event of specified dividend payments. The KVK Warrant is exercisable until OctoberDecember 31, 2023, 24,2023.The Company determined that the KVK Warrant qualifies as a derivative under ASC 815 and should be recorded as a liability and stated at fair value each reporting period. The Company calculates the fair value of the KVK Warrant using a probability-weighted Black-Scholes option pricing model. Changes in fair value resulting from changes inliability associated with these warrants and the inputs to the Black Scholes model are accounted for as changes in the fair value of the derivative under ASC 815Put Option was approximately $11.5 million and are recorded as$16.1 million, respectively. The fair value adjustment related to derivativethese warrants and warrant liability in the unaudited condensed consolidated statementsPut Option was approximately $4.6 million of operations.  

Onincome and $1.5 million of expense for the January 12,three 2021, the Company issued warrants to purchase 12,078,361 shares of the Company’s common stock (collectively, the “Offering Warrants”) in the Public Offering. The Offering Warrants were immediately exercisable and expire on the fifth anniversary of their issuance date, at an exercise price per share of common stock equal to $6.50 per share. The Offering Warrants meet the equity classification requirements and thus are recorded in additional paid-in capital on the unaudited condensed consolidated balance sheets. As ofmonths ended March 31, 2023,2024, 3,461,968 Offering Warrants have been exercised for 3,030,991 shares of common stock and gross proceeds of approximately $16.9 million. 2023, respectively.

On January 12,2021, the Company issued a warrant to Roth Capital Partners ("Roth") to purchase 806,932 shares of the Company’s common stock and the exercise price is $8.125 per share. In connection with the closing of the Roth's partial exercise of its over-allotment option, on February 3, 2021, Roth was issued an additional warrant to purchase 18,702 shares of common stock. As of March 31, 2023, 400,000 of these warrants have been exercised for 400,000 shares of common stock and gross proceeds of approximately $3.3 million.

January 2021Warrant Exercise Inducement Letters and Issuance of Warrants

On January 26, 2021, the Company entered into warrant exercise inducement offer letters ( “January 2021 Inducement Transaction”) with certain holders of warrants issued in the Public Offering (the “January 2021 Inducement Warrants”) to purchase up to 7,944,430 shares of the Company’s common stock (the "January 2021 Inducement Warrants"). The January 2021 Inducement Warrants were immediately exercisable and expire on the fifth anniversary of their issuance date, at an exercise price per share of common stock equal to $6.36 per share. As of March 31, 2023, 1,676,921 January 2021 Inducement Warrants have been exercised for 1,676,921 shares of common stock and gross proceeds of approximately $10.7 million. 

June 2021Warrant Exercise Inducement Letters and Issuance of Warrants

On June 18, 2021, the Company entered into warrant exercise inducement offer letters ( “June 2021 Inducement Transaction”) with certain holders of warrants issued in the January 2021 Inducement Transaction discussed above (the "January 2021 Inducement Warrants") pursuant to which such holders agreed to exercise for cash their January 2021 Inducement Warrants to purchase 6,117,509 shares of the Company’s common stock in exchange for the Company’s agreement to issue new warrants to purchase up to 1,529,379 shares of the Company's common stock (the “June 2021 Inducement Warrants”) on substantially the same terms as the January 2021 Inducement Warrants. The June 2021 Inducement Warrants were immediately exercisable and expire on December 31, 2026, at an exercise price per share of common stock equal to $16.50 per share. As of March 31, 2023, noJune 2021 Inducement Warrants have been exercised.

The Company maintains a stock-based compensation plan (the “Incentive Stock Plan”) that governs stock awards made to employees and directors prior to completion of the IPO.  

In November 2014, the Board of Directors of the Company ("the Board"), and in April 2015, the Company’s stockholders, approved the Company’s 2014 Equity Incentive Plan (the “2014 Plan”), which became effective in April 2015. The 2014 Plan provides for the grant of stock options, other forms of equity compensation, and performance cash awards. In June 2021, the Company's stockholders approved an Amended and Restated 2014 Equity Incentive Plan (the "A&R 2014 Plan"), following its adoption by the Board in April 2021, which among other things added 4,900,000 shares to the maximum number of shares of common stock to be issued under the plan and extended the annual automatic increases (discussed further below) untiluntil January 1, 2031 and eliminated individual grant limits that applied under the 2014 Plan to awards that were intended to comply with the exemption for "performance-based compensation" under Code Section 162(m). The maximum number of shares of common stock that may be issued under the A&R 2014 Plan is 8,271,4979,932,883 as of March 31, 2023. 2024. The number of shares of common stock reserved for issuance under the A&R 2014 Plan will automatically increase on January 1 of each year, beginning on January 1, 2016, and ending onuntil and including January 1, 2031, by 4% of the total number of shares of the Company’s capital stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares determined by the Board. Pursuant to the terms of the 2014 Plan, on January 1, 2023,2024, the common stock reserved for issuance under the 2014 Plan automatically increased by 1,381,612 1,661,386 shares.

During the three months ended March 31, 2023,2024, and716,875 stock options were exercised. During the 2022,three months ended March 31, 2023, no stock options were exercised.

In June 2021, the Company's stockholders approved an Employee Stock Purchase Plan (the "ESPP"), following its adoption by the Board in April 2021. The maximum number of shares of common stock that may be issued under the ESPP is 1,500,000. The first offering period under the ESPP began on October 1, 2021, and the first purchase date occurred on May 31, 2022. As of March 31, 2023,2024, 82,635159,828 shares have been issued under the ESPP.

In January 2023, the Board approved the 2023 Employment Inducement Award Plan (the "2023"2023 Plan"). The maximum number of shares of common stock that may be issuedwere initially available for issuance under the 2023 Plan iswas 1,500,000. In February 2024, our Board approved an amendment to the 2023 Plan to increase the aggregate number of shares of common stock available for issuance under the 2023 Plan from 1,500,000 to 4,500,000 shares.

In May 2023, the Board approved the Ninth Amended and Restated Non-Employee Director Compensation Policy (the “Non-Employee Director Compensation Policy”). The equity compensation made pursuant to the Non-Employee Director Compensation Policy will be granted under the A&R 2014 Plan.

Stock-based compensation expense recorded under the Incentive Stock Plan, 2014 Plan, A&R 2014 Plan, ESPP and ESPP2023 Plan is included in the following line items in the accompanying unaudited condensed consolidated statements of operations (in thousands):

There was no stock-based compensation expense related to performance-based awards recognized during the three months ended March 31, 2023,2024, orand 2022.2023. 

As a result of the modification of certain stock options in connection with the Transition Agreement, as further discussed in Note J, the Company recaptured $0.9 million in stock-compensation expense and recognized $0.4 million in severance expense for the three months ended March 31, 2023. 

The accounting standard for fair value measurements provides a framework for measuring fair value and requires disclosures regarding fair value measurements. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date, based on the Company’s principal or, in absence of a principal, most advantageous market for the specific asset or liability.

The Company uses a three-tier fair value hierarchy to classify and disclose all assets and liabilities measured at fair value on a recurring basis, as well as assets and liabilities measured at fair value on a non-recurring basis, in periods subsequent to their initial measurement. The hierarchy requires the Company to use observable inputs when available, and to minimize the use of unobservable inputs, when determining fair value. The three tiers are defined as follows:

The carrying amounts of certain financial instruments, including cash and cash equivalents, investments, and accounts payable and accrued expenses, approximate their respective fair values due to the short-term nature of such instruments.

Assets and Liabilities Measured at Fair Value on a Recurring Basis

The Company evaluates its financial assets and liabilities subject to fair value measurements on a recurring basis to determine the appropriate level in which to classify them for each reporting period. This determination requires significant judgments to be made. The following table summarizes the conclusions reached regarding fair value measurements as of March 31, 2023, 2024,and December 31, 20222023 (in thousands):

The common stock warrant liabilities were recorded at fair value using the Black-Scholes option pricing model. The following assumptions were used in determining the fair value of the warrant liabilities valued using the Black-Scholes option pricing model as of March 31, 2024, and December 31, 2023:

The Company’s OTA Warrant liability, embedded Warrant Put Option and securities arefollowing table is a reconciliation for the common stock warrant liabilities measured at fair value on a recurring basis. As ofvalue using Level March 31, 2023, 3and December 31, 2022, the OTA Warrant liability and the embedded Warrant Put Option are reported on the unaudited condensed consolidated balance sheets in derivative and warrant liability. As of March 31, 2023, and December 31, 2022, the securities are reported on the unaudited condensed consolidated balance sheets in securities at fair value. The Company used a Monte Carlo simulation to value the OTA Warrant liability and embedded Warrant Put Option for all periods presented herein. Significant unobservable unobservable inputs used in measuring the fair value of these financial instruments included the Company’s estimated enterprise value, an estimate of the timing of a liquidity or fundamental change event and a present value discount rate. Changes in the fair value of the OTA Warrant liability and embedded Warrant Put Option are reflected in the unaudited condensed consolidated statements of operations for(in thousands):

For the three months ended March 31, 2023,2024, and 2022,2023, as a fair value adjustment related to derivative and warrant liability.

The derivative liability for the OTA Warrant was $3,000 and $1,000 at March 31, 2023, and December 31, 2022, respectively. The derivative liability for the embedded Warrant Put Option was $0 at March 31, 2023, and December 31, 2022. A 10% increasechanges in the enterprise value would result in a negligible increase in the estimated fair value of the OTA Warrant liabilitywarrant liabilities primarily resulted from the volatility of the Company's common stock and the estimated fair value of the embedded Warrant Put Option liability. In addition, the Company assumed a weighted-average probability of a liquidity event occurring of approximately 48% with an estimated probability-weighted value of approximately $38.5 million and a weighted-average probability of a fundamental change event occurring of approximately 30% with an estimated probability-weighted value of approximately $463.8 million, respectively, with estimated timing in each scenario of the fourth quarter of 2023.

The Company’s KVK Warrant liability is measured at fair value on a recurring basis. As of March 31, 2023, and December 31, 2022, the KVK Warrant liability is reported on the unaudited condensed consolidated balance sheets in derivative and warrant liability. The Company estimates the fair value of the KVK Warrant using a probability-weighted Black-Scholes option-pricing model, which requires the use of subjective assumptions, including the expected term of the warrant, the expected stock price volatility, expected dividend yield and the risk-free interest rate for the expected term of the warrant. The expected term represents the period of time the warrant is expected to be outstanding. For the KVK Warrant, the Company used an expected term equal to the contractual term of the warrant. Expected volatility is based on the Company's historical volatility since the IPO. The Company assumes no dividend yield because dividends are not expected to be paid in the near future, which is consistent with the Company’s history of not paying dividends. Changes in the fair value of the KVK Warrant liability are reflected in the unaudited condensed consolidated statements of operations for the three months ended March 31, 2023, and 2022, as a fair value adjustment related to derivative and warrant liability.rates.