Note 9 - Stockholders’ Equity

Registration Statements

On April 23, 2021, the Company filed a shelf registration statement on Form S-3 (File No. 333-255476) (the “2021 S-3”), which was declared effective on May 24, 2021. Under the 2021 S-3, the Company was able to sell up to a total of $200.0 million of its securities. The 2021 S-3 expired on May 24, 2024. The Company sold approximately $4.4 million of securities under the 2021 S-3.

On May 31, 2024, the Company filed a shelf registration statement on Form S-3 (File No. 333-279891) (the “2024 S-3”), which was declared effective on June 12, 2024. Under the 2024 S-3, the Company may sell up to a total of $40.0 million of its securities. As of June 30, 2024, approximately $37.5 million of the 2024 S-3 remains available for sales of securities. The 2024 S-3 expires on June 12, 2027.

As of the filing of this Form 10-Q, the Company is subject to the General Instruction I.B.6 to Form S-3, known as the “baby shelf rules,” which limit the number of securities it can sell under its registration statements on Form S-3.

May 2024 Public Offering

​

On April 29, 2024, the Company commenced a best efforts public offering with an institutional investor (the “Investor”) (the “May 2024 Offering”) of an aggregate of (i) 1,160,000 shares of common stock, (ii) pre-funded warrants (the “May 2024 Pre-Funded Warrants”) to purchase up to an aggregate of 15,717,638 shares of common stock (the “May 2024 Pre-Funded Warrant Shares”), (iii) Series A-1 warrants (the “Series A-1 Warrants”) to purchase up to an aggregate of 16,877,638 shares of common stock (the “Series A-1 Warrant Shares”), (iv) Series A-2 warrants (the “Series A-2 Warrants”) to purchase up to an aggregate of 16,877,638 shares of common stock (the “Series A-2 Warrant Shares”), and (v) Series A-3 warrants (the “Series A-3 Warrants,” and together with the Series A-1 Warrants and Series A-2 Warrants, the “Warrants”) to purchase up to an aggregate of 16,877,638 shares of common stock (the “Series A-3 Warrant Shares”). Each share of common stock or May 2024 Pre-Funded Warrant was sold together with one Series A-1 Warrant to purchase one share of common stock, one Series A-2 Warrant to purchase one share of common stock, and one Series A-3 Warrant to purchase one share of common stock. The public offering price for each share of common stock and accompanying Warrants was $0.237, and the public offering price for each May 2024 Pre-Funded Warrant and accompanying Warrants was $0.2369. The May 2024 Pre-Funded Warrants have an exercise price of $0.0001 per share, were exercisable immediately and will expire when exercised in full. Each Warrant has an exercise price of $0.237 per share, will be exercisable beginning on the effective date of stockholder approval of the issuance of the shares upon exercise of the Warrants (the “Warrant Stockholder Approval”). The Series A-1 Warrant will expire on the five-year anniversary of the Warrant Stockholder Approval. The Series A-2 Warrant will expire on the twenty-four-month anniversary of the Warrant Stockholder Approval. The Series A-3 Warrant will expire on the nine-month anniversary of the Warrant Stockholder Approval. The Warrants contain customary anti-dilution adjustments to the exercise price, including for share splits, share dividends, rights offering and pro rata distributions.

​

The net proceeds of the May 2024 Offering, after deducting the fees and expenses of the Placement Agent (as defined below), described in more detail below, and other offering expenses payable by us, but excluding the net proceeds, if any, from the exercise of the Warrants, was approximately $3.2 million. The May 2024 Offering closed on May 2, 2024.

In connection with the May 2024 Offering, the Company also entered into a warrant amendment agreement (the “Warrant Amendment Agreement”) with the Investor. Under the Warrant Amendment Agreement, the Company agreed to amend certain existing warrants to purchase up to 2,588,236 shares of common stock that were previously issued in October 2023 to the Investor, with an exercise price of $1.58 per share (the “Existing Warrants”), in consideration for their purchase of the securities in the May 2024 Offering, as follows: (i) lower the exercise price of the Existing Warrants to $0.237 per share, (ii) provide that the Existing Warrants, as amended, will not be exercisable until the receipt of Warrant Stockholder Approval for the exercisability of the Warrants in the May 2024 Offering, and (iii) extend the original expiration date of the Existing Warrants by five years following the receipt of such Warrant Stockholder Approval. The Warrant Amendment Agreement became effective on May 2, 2024.

​

June 2024 Registered Direct Offering and Concurrent Private Placement of Warrants (the “June 2024 Offering”)

​

On June 19, 2024, the Company entered into a Securities Purchase Agreement (the “Purchase Agreement”) with an institutional investor (the “June 2024 Investor”), pursuant to which the Company agreed to issue and sell, in a registered direct offering priced at-the-market under the rules of Nasdaq (the “Registered Direct Offering”), (i) 3,025,000 shares of common stock, at a price per Share of $0.41 and (ii) pre-funded warrants (the “Pre-Funded Warrants”) to purchase up to 3,105,000 shares of our common stock, at a price per Pre-Funded Warrant equal to $0.4099, the price per share of common stock, less $0.0001.

The Pre-Funded Warrants were sold, in lieu of shares of common stock to the June 2024 Investor. The Pre-Funded Warrants have an exercise price of $0.0001 per share, became exercisable upon issuance and remain exercisable until exercised in full.

The Registered Direct Offering closed on June 21, 2024. The Company intends to use the net proceeds of approximately $2.1 million from the Registered Direct Offering for general corporate purposes and working capital requirements.

In a concurrent private placement, pursuant to the terms of the Purchase Agreement, the Company also agreed to issue and sell to the June 2024 Investor unregistered warrants (the “Private Placement Warrants”) to purchase up to 6,130,000 shares of common stock, at an offering price of $0.41 per Private Placement Warrant to purchase one share of common stock (the “Private Placement” and, together with the Registered Direct Offering, the “Offerings”) (which offering price was included in the purchase price per share of common stock or Pre-Funded Warrant). The Private Placement Warrants have an exercise price of $0.41 per share (subject to customary adjustments as set forth in the Private Placement Warrants), were exercisable upon issuance and will expire five years from the date of issuance. The Private Placement Warrants contain customary anti-dilution adjustments to the exercise price, including for share splits, share dividends, rights offering and pro rata distributions. The Private Placement Warrants were subsequently registered in July 2024 on Form S-1 (File No. 333-280927).

H.C. Wainwright & Co., LLC (“Wainwright” and together with the June 2024 Investor, the “Selling Stockholders”) acted as the exclusive placement agent in connection with the Offerings under an Engagement Letter, dated as of June 18, 2024, between us and Wainwright (the “Engagement Letter”). Pursuant to the Engagement Letter, we issued to Wainwright (or its designees) warrants to purchase up to 367,800 shares of common stock (the “Wainwright Warrants” and, together with the Private Placement Warrants, the “2024 Warrants”). The Wainwright Warrants have substantially the same terms as the Private Placement Warrants, except that the Wainwright Warrants will expire five years from the commencement of the sales of the Offerings and have an exercise price of $0.5125 per share (subject to customary adjustment as set forth in the Wainwright Warrants), representing 125% of the purchase price per share of common stock in the Registered Direct Offering.

​

At-the-Market Offering

In July 2018, the Company entered into an At-the-Market Issuance Sales Agreement (the “Mustang ATM”) with B. Riley Securities, Inc. (formerly B. Riley FBR, Inc.), Cantor Fitzgerald & Co., National Securities Corporation (now B. Riley FBR, Inc.), and Oppenheimer & Co. Inc. (each an “Agent” and collectively, the “Agents”), relating to the sale of shares of common stock pursuant to the 2020 S-3. Under the Mustang ATM, the Company pays the Agents a commission rate of up to 3.0% of the gross proceeds from the sale of any shares of common stock. On December 31, 2020, the Mustang ATM was amended to add H.C. Wainwright & Co., LLC as an Agent. On April 14, 2023, the Mustang ATM was amended to add the limitations imposed by General Instruction I.B.6 to Form S-3 and remove Oppenheimer & Co., Inc. as an Agent. On May 31, 2024, the Company delivered notice to the Agents to terminate the Mustang ATM, which was effective June 5, 2024.

On May 31, 2024, the Company entered into an At-the-Market Offering Agreement (the “Offering Agreement”) with H.C. Wainwright (the “Manager”) under which the Company may offer and sell, from time to time at its sole discretion, shares of its common stock through or to the Manager pursuant to the 2024 S-3. Under the Offering Agreement, the Company pays the Manager a commission of 3.0% of the gross proceeds from the sales of any shares of common stock. The Company

will also reimburse the Manager for certain expenses incurred in connection with the Offering Agreement. The Company and the Manager may each terminate the Sales Agreement at any time upon specified prior written notice.

​

During the six months ended June 30, 2024 and 2023, no shares of common stock were issued under the Mustang ATM Agreement or the Offering Agreement.

​

Equity Incentive Plan

The Company has in effect the 2016 Incentive Plan (the “Incentive Plan”). The Incentive Plan was adopted in 2016 by the Company’s stockholders and the compensation committee of the Company’s board of directors and is authorized to grant stock-based awards to directors, officers, employees and consultants. The plan initially authorized grants to issue up to 133,333 shares of authorized but unissued common stock, expires 10 years from adoption, and limits the term of each option to no more than 10 years from the date of grant. In June 2018, the Company’s stockholders approved an amendment to the Incentive Plan to increase the number of authorized shares issuable by 200,000 shares, for a total of 333,333 shares. In June 2021, the Company’s stockholders approved an amendment to the Incentive Plan to increase the number of authorized shares issuable by 200,000 shares, for a total of 533,333 shares. In June 2022, the Company’s stockholders approved an amendment to the Incentive Plan to increase the number of authorized shares issuable by 200,000 shares, for a total of 733,333 shares.

As of June 30, 2024, 394,393 shares were available for future issuance under the Incentive Plan.

Stock Options

The following table summarizes stock option activities for the six months ended June 30, 2024:

​

​

As of June 30, 2024, the Company had no unrecognized stock-based compensation expense related to options. The Company accounts for forfeited awards as they occur as permitted.

​

Restricted Stock

The following table summarizes restricted stock award activities for the six months ended June 30, 2024:

​

​

As of June 30, 2024, the Company had unrecognized stock-based compensation expense related to restricted stock of $0.3 million, which is expected to be recognized over the remaining weighted average vesting period of approximately 1.6 years.

Restricted Stock Units

Certain employees and consultants have been awarded restricted stock units with time-based vesting. The following table summarizes restricted stock units’ activities for the six months ended June 30, 2024:

​

​

As of June 30, 2024, the Company had unrecognized stock-based compensation expense related to restricted stock units of approximately $57,000, which is expected to be recognized over the remaining weighted average vesting period of approximately 1.9 years.

The following table summarizes stock-based compensation expense for the three and six months ended June 30, 2024 and 2023 (in thousands):

​

​

On April 12, 2024, the Company reduced its workforce by approximately 81 percent, which resulted in the forfeiture of a significant number of outstanding restricted stock units and the reversal of previously incurred stock-based compensation expense.

​

Employee Stock Purchase Plan

​

Eligible employees can purchase the Company’s common stock at the end of a predetermined offering period at 85% of the lower of the fair market value at the beginning or end of the offering period.  The Employee Stock Purchase Plan (“ESPP”) is compensatory and results in stock-based compensation expense. The ESPP was initially authorized in 2019 to sell up to 26,667 shares of authorized but unissued common stock. In June 2021, the Company’s stockholders approved an amendment to the ESPP to increase the number of authorized shares issuable by 40,000 shares. In addition, in June 2023, the Company’s stockholders approved an amendment to the ESPP to increase the number of authorized shares issuable thereunder by 400,000 for a total of 466,667 shares.

​

As of June 30, 2024, 128,352 shares have been purchased and 338,315 shares are available for future sale under the Company’s ESPP.

Warrants

A summary of warrant activities for the six months ended June 30, 2024, is presented below:

​

​

Upon the cashless exercise of warrants, the Company will issue new shares of common stock. In connection with the Company’s Registered Direct Offering on October 26, 2023, the Company issued pre-funded warrants to purchase up to 1,668,236 shares of common stock, and in a concurrent private placement, the Company issued unregistered warrants to purchase up to 2,588,236 shares of common stock, and the resale of the underlying shares of common stock were subsequently registered in April 2024 on Form S-1 (File No. 333-275997). In connection with these offerings, H.C. Wainwright received Placement Agent Warrants to purchase up to 155,294 shares of common stock. In connection with the Public Offering the Company completed in May 2024, the 2,588,236 unregistered warrants were repriced from the original exercise price of $1.58 to $0.237.

​

In connection with the May 2024 Offering, the Company issued pre-funded warrants to purchase up to 15,717,638 shares of common stock and issued three series of warrants to purchase up to 50,632,914 shares of common stock. In connection with these offerings, H.C. Wainwright received Placement Agent Warrants to purchase up to 1,012,658 shares of common stock.

​

In connection with the Registered Direct Offering, the Company issued pre-funded warrants to purchase up to 3,105,000 shares of common stock, and in the concurrent Private Placement, the Company issued unregistered warrants to purchase up to 6,130,000 shares of common stock, the resale of the underlying shares of common stock were subsequently registered in July 2024 on Form S-1 (File No. 333-280927). In connection with these offerings, H.C. Wainwright received Placement Agent Warrants to purchase up to 367,800 shares of common stock.

​

During the six months ended June 30, 2024, all of the 1,668,236 pre-funded warrants issued in the October Registered Direct Offering were exercised at an exercise price of $0.001, and all of the 18,822,638 pre-funded warrants issued in the May 2024 Offering and the June Registered Direct Offering were exercised at an exercise price of $0.0001.