Note 8 - Stockholders’ Equity

Registration Statements

On October 23, 2020, the Company filed a shelf registration statement No. 333-249657 on Form S-3 (the “2020 S-3”), which was declared effective on December 4, 2020. Under the 2020 S-3, the Company may sell up to a total of $100.0 million of its securities. As of March 31, 2021, approximately $37.8 million of the 2020 S-3 remains available for sales of securities.

Common Stock

At-the-Market Offering

On July 13, 2018, the Company filed a shelf registration statement No. 333-226175 on Form S-3, as amended on July 20, 2018 (the “2018 Mustang S-3”), which was declared effective in August 2018. Under the 2018 Mustang S-3, the Company may sell up to a total of $75.0 million of its securities. In connection with the 2018 Mustang S-3, 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, and Oppenheimer & Co. Inc. (each an “Agent” and collectively, the “Agents”), relating to the sale of shares of common stock. 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.

During the three months ended March 31, 2021, the Company issued approximately 11.6 million shares of common stock at an average price of $4.17 per share for gross proceeds of $48.4 million under the Mustang ATM. In connection with these sales, we paid aggregate fees of approximately $0.9 million for net proceeds of approximately $47.5 million. During the three months ended March 31, 2020, the Company issued approximately 1.2 million shares of common stock at an average price of $3.93 per share for gross proceeds of $5.0 million under the Mustang ATM. In connection with these sales, we paid aggregate fees of approximately $0.1 million for net proceeds of approximately $4.9 million.

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Pursuant to the Founders Agreement, we issued 325,221 shares of common stock to Fortress at a weighted average price of $4.16 per share for the three months ended March 31, 2021 and recorded 63,688 shares issuable to Fortress in connection with the Mustang ATM offering noted above. During the three months ended March 31, 2020, we issued 31,220 shares of common stock to Fortress at a weighted average price of $4.00 per share in connection with the Mustang ATM.

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Equity Incentive Plan

The Company has in effect the 2016 Incentive Plan (the “Incentive Plan”). The Incentive Plan was adopted in 2016 by our 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 2,000,000 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 3,000,000 shares, for a total of 5,000,000 shares.

As of March 31, 2021, 636,585 shares are available for issuance under the Incentive Plan.

Stock Options

The following table summarizes stock option activities for the three months ended March 31, 2021:

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As of March 31, 2021, the Company had unrecognized stock-based compensation expense related to options of $0.1 million, which is expected to be recognized over the remaining weighted average vesting period of approximately 0.6 years.

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Restricted Stock

The following table summarizes restricted stock award activities for the three months ended March 31, 2021:

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As of March 31, 2021, the Company had unrecognized stock-based compensation expense related to restricted stock of $0.4 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 three months ended March 31, 2021:

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As of March 31, 2021, the Company had unrecognized stock-based compensation expense related to restricted stock units of approximately $4.1 million, 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 months ended March 31, 2021 and 2020 (in thousands).

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Employee Stock Purchase Plan

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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.

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For the three months ended March 31, 2021 and 2020, 55,963 and 68,351 shares, respectively, have been purchased and   203,181 shares are available for future sale under the Company’s ESPP.  The Company received proceeds of $0.2 million and $0.2 million for the three months ended March 31, 2021 and 2020, respectively.

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Warrants

A summary of warrant activities for the three months ended March 31, 2021 is presented below:

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Upon the cashless exercise of warrants, the Company will issue new shares of common stock.