4. Stockholders’ Equity

Equity Transactions

February 2024 Offering

In February 2024, the Company entered into an underwriting agreement (the “Underwriting Agreement”) with Craig-Hallum Capital Group LLC and Laidlaw & Company (UK) Ltd. (collectively, the “Underwriters”), relating to the issuance and sale of 427,886 common stock units (the “Common Stock Units”) at a public offering price of $8.16 per Common Stock Unit and, to certain investors, 491,221 pre-funded warrant units (the “PFW Units”) at a public offering price of $8.1588 per PFW Unit (the “February 2024 Offering”). Each Common Stock Unit consisted of (i) one share of common stock, (ii) a Series A Warrant to purchase one share of common stock (the “Series A Warrant”), (iii) a Series B Warrant to purchase one share of common stock (the “Series B Warrant”), and (iv) a Series C Warrant to purchase one share of common stock (the “Series C Warrant”). Each PFW Unit consisted of (i) a pre-funded warrant to purchase one share of common stock (the “Pre-Funded Warrants”), (ii) a Series A Warrant, (iii) a Series B Warrant, and (iv) a Series C Warrant. The Company also issued warrants to the Underwriters to purchase up to 45,955 shares of common stock, equal to 5% of the securities sold in the February 2024 Offering (the “Representatives’ Warrants”). The Series A Warrants are fully exercisable and are recognized as a freestanding financial instruments. In accordance with the terms and provisions of the Series C Warrants, the Series C Warrants were not exercisable, in part or in whole, at any time unless the Series B Warrants had been exercised. If Series B Warrants were not exercised before November 13, 2024, the corresponding Series C Warrants were no longer deemed outstanding and could not be exercised. Furthermore, the Series B Warrants and Series C Warrants could not be transferred by the holder without the consent of the Company, and, therefore the Series B Warrants and Series C Warrants were accounted for as a single unit of account.

Net cash proceeds from the February 2024 Offering was $6.2 million after deducting underwriter and offering expenses. The Pre-Funded Warrants, Series A Warrants, Series B Warrants, and Series C Warrants are equity classified and were recognized as additional paid-in capital in the balance sheets. The Representatives’ Warrants were accounted for under ASC 718, Compensation — Stock Compensation, and were recognized as an equity issuance cost at their grant date fair value within additional paid-in capital in the balance sheets.

August 2024 Shelf Registration Statement

On August 29, 2024, the Company filed a universal shelf registration statement on Form S-3 (the “Shelf Registration Statement”), covering the offering of up to $50.0 million of common stock, preferred stock, debt securities, warrants, and/or units, subject to the “Baby Shelf Limitation” which limits the amount that the Company can offer and sell to up to one-third of its public float during any 12-month period so long as our public float remains below $75.0 million. The Shelf Registration Statement was declared effective by the SEC on September 6, 2024.

As of June 30, 2025, there have been no shares of common stock, preferred stock, debt securities, warrants, and/or units issued under the Shelf Registration Statement.

At The Market Equity Offering

The Company had previously entered into a Sales Agreement (the “Sales Agreement”) with H.C. Wainwright & Co., LLC (“Wainwright”), under which the Company may, from time to time, sell shares of its common stock having an aggregate offering price of up to approximately $1.9 million through Wainwright (the “ATM Offering”). The Shelf Registration Statement included a prospectus covering the offering, issuance and sale of up to approximately $1.9 million of the Company’s common stock from time to time through the ATM Offering (the “ATM Prospectus”). In November 2024, the Company filed a prospectus supplement to amend and supplement the ATM Prospectus to update the amount of shares it is eligible to sell under the “Baby Shelf Limitation” to $3.1 million under the Sales Agreement.

The Company did not issue any shares of common stock pursuant to the ATM Offering during the three months and six months ended June 30, 2025.

Warrant Amendments

In each of March, June and September 2024, the Company entered into substantially similar amendments with certain holders of its Series B Warrants and Series C Warrants (individually, the “March 2024 Warrant Amendment,” “June 2024 Warrant Amendment,” and the “September 2024 Warrant Amendment,” respectively and collectively, the “Warrant Amendments”). Pursuant to the Warrant Amendments, to the extent a holder exercised its Series B Warrants prior to the exercise deadlines set forth in the respective Warrant Amendment (the “Amendment Exercise Deadline”), the holder’s corresponding Series C Warrants vested and became exercisable for the lesser of (i) three times the number of Series B Warrants exercised by the Holder and (ii) the total number of Series C Warrants outstanding to the holder. Following each Amendment Exercise Deadline, if the holder exercised any remaining Series B Warrants, the remaining Series C Warrants, if any, vested and became exercisable on a one-for-one basis as to the same number of Series B Warrants exercised.

The Warrant Amendments allowed a holder to elect to receive Pre-Funded Warrants upon exercise of Series B Warrants and Series C Warrants in lieu of shares of the Company’s common stock, at a purchase price of $8.1588 per warrant exercised and an exercise price of $0.0012 per Pre-Funded Warrant.

Net cash proceeds from the March Warrant Amendment, the June Warrant Amendment, and the September 2024 Warrant Amendment were $1.2 million, $0.3 million and $0.4 million, respectively, after deducting underwriter commissions and offering expenses. The Warrant Amendments were entered into to encourage the exercise of Series B Warrants in order to obtain capital to meet the Minimum Stockholders’ Equity Requirement as more fully discussed in Note 1. Organization and Basis of Presentation. The Warrant Amendments neither changed the number of shares of common stock underlying each series of warrants nor its equity classification. The incremental change in fair value from the Warrant Amendments was accounted for as equity issuance costs and recognized within additional paid-in capital in the balance sheets.

September 2024 Exercise Price Warrant Amendment

In September 2024, the Company also entered into an amendment with certain holders of its Series A Warrants, Series B Warrants and Series C Warrants (the “September 2024 Exercise Price Warrant Amendment”). Pursuant to the September 2024 Exercise Price Warrant Amendment, such holders who agreed to pay a non-refundable up-front payment of $3.99 per Series A Warrant or Series C Warrant prior to September 30, 2024 deadline (as defined in the September 2024 Exercise Price Amendment) had the exercise price reduced for each of the Series A Warrants and Series C Warrants from $8.16 to $0.01 (such Series A Warrants and Series C Warrants modified to have a reduced exercise price referred to as the “Modified Series A Warrants” and “Modified Series C Warrants”). To the extent such holder did not elect to modify all outstanding Series A Warrants and Series C Warrants, the remaining Series A Warrants and Series C Warrants held by each holder retained an exercise price of $8.16 per Series A Warrant or Series C Warrant.

Net cash proceeds from the September 2024 Exercise Price Warrant Amendment were $2.5 million after deducting underwriter and offering expenses. The September 2024 Exercise Price Warrant Amendment was entered to encourage the modification of Series A Warrants and Series C Warrants in order to obtain capital to meet the Minimum Stockholders’ Equity Requirement. The September 2024 Exercise Price Warrant Amendment neither changed the number of shares of Common Stock underlying each series of warrants nor its equity classification. The incremental change in fair value from the September 2024 Exercise Price Warrant Amendment was an equity issuance cost and was recognized within additional paid-in capital in the balance sheets.

In connection with the September 2024 Exercise Price Warrant Amendment, the Company entered into a letter agreement, dated September 27, 2024 (the “Letter Agreement”), with certain affiliates of Nantahala Capital Management, LLC (collectively, “Nantahala”), pursuant to which, subject to certain limitations, the Company provided Nantahala the right to appoint (or cause to be nominated) (i) one member of the Company’s board of directors (the “Board”) and one member of each Board committee so long as Nantahala, together with its affiliates, beneficially owns at least 5.0% of the Company’s outstanding shares of common stock and (ii) two members of the Board so long as Nantahala, together with its affiliates, beneficially owns at least 15.0% of the Company’s outstanding shares of common stock, subject to certain exceptions.

Warrants

Each of the outstanding warrants is convertible on a one-for-one basis into the Company’s common stock and are fully exercisable as of June 30, 2025. The following table is a summary of the Company’s warrants outstanding as of June 30, 2025:

Stock-Based Compensation

Stock Options

In January 2025, the number of shares of common stock available for issuance under the 2013 Equity Incentive Award Plan (the “2013 Plan”) was increased by 89,161 shares as a result of the automatic increase provision in the 2013 Plan. Stock-based compensation expense includes charges related to stock option grants. The Company measures stock-based compensation expense based on the grant date fair value of any awards granted to its employees. Such expense is recognized over the period of time that employees provide service and earn rights to the awards.

During the six months ended June 30, 2025 and 2024, the Company granted stock options to purchase 152,328 and 6,352 shares of the Company’s common stock, respectively.

Employee Stock Purchase Plan

Stock-based compensation expense also includes charges related to common stock issued under the Amended and Restated 2013 Employee Stock Purchase Plan (the “ESPP”). The Company allows eligible employees to purchase shares of the Company’s common stock through payroll deductions at a price equal to 85% of the lesser of the fair market value of the Company’s common stock on the first trading day of the offering period or on the applicable purchase date. The offering period is determined by the compensation committee and may be up to 27 months long. Current offering periods commence on each of September 1 and March 1 during the term. Purchase dates will be set for the last trading day in each six-month period and will occur on each of August 31 and February 28 (unless such days are not trading days). In January 2025, the number of shares of common stock available for issuance under the ESPP was increased by 14,860 shares as a result of the automatic increase provision in the ESPP. During the third quarter of 2024, an offering period was initiated. During the six months ended June 30, 2025, there were 6,849 shares of common stock issued pursuant to the Company’s ESPP, for gross proceeds of approximately $25,000.

During the six months ended June 30, 2024, no employees participated in the ESPP plan and as such, no ESPP awards were valued using the Black-Scholes option pricing-model. The estimated fair value of each ESPP award granted was determined on

As of June 30, 2025, there was approximately $0.8 million of unrecognized compensation costs related to outstanding options, which are expected to be recognized over a weighted-average period of 2.8 years.

As of June 30, 2025, there was approximately $7,000 of unrecognized compensation costs related to the ESPP, which are expected to be recognized over a weighted-average period of 0.2 years.