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Equity Incentive Plans | 6 Months Ended
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Jun. 30, 2025
Equity Incentive Plans |
Equity Incentive Plans | 7. Equity Incentive Plans Equity Incentive Plans On January 20, 2017, the Company’s stockholders approved the 2016 Equity Incentive Plan (the “2016 Plan”). Beginning on January 1, 2018, the number of shares of common stock authorized for issuance pursuant to the 2016 Plan was increased each January 1 by an amount equal to 4% of the Company’s outstanding common stock as of the end of the immediately preceding calendar year or such lesser amount as determined by the compensation committee of the Company’s Board of Directors. On June 16, 2022, the Company’s stockholders approved the 2022 Equity Incentive Plan (the “2022 Plan”), which provides for a total of 750,000 new shares of the Company’s common stock to be granted. In addition, on June 16, 2023, and July 2, 2024, stockholders approved new shares of the Company’s common stock to be added to the 2022 Plan for future issuance of 2,250,000 and 2,000,000, respectively. As of June 30, 2025, there were 3,922,812 shares available for grant under the Company’s equity incentive plans. A summary of stock option activity under the Equity Plans is as follows: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ | ​ |  | Weighted |  | ​ | ​ |  | ​
​ | ​ | ​ | ​ |  | Average |  | Weighted | ​ |  | Aggregate
​ | ​ | ​ | ​ |  | Exercise Price |  | Average Remaining | ​ |  | Intrinsic
​ |  | Options | ​ |  | Per Share |  | Life in Years | ​ |  | Value
Outstanding at December 31, 2024 |  | 6,416,744 | ​ | $ | 8.43 |  | 8.43 | ​ | $ | 1,937
Exercised | ​ | (6,667) | ​ | $ | 2.40 | ​ | ​ | ​ | ​ | ​
Forfeited |  | (1,378,104) | ​ | $ | 7.55 |  | ​ | ​ | ​ | ​
Outstanding at June 30, 2025 |  | 5,031,973 | ​ | $ | 8.68 |  | 6.00 | ​ | $ | —
Options exercisable at June 30, 2025 |  | 3,639,701 | ​ | $ | 10.98 |  | 4.94 | ​ | ​ | ​
Options vested and expected to vest at June 30, 2025 |  | 5,031,973 | ​ | $ | 8.68 |  | 6.00 | ​ | $ | —
​ The grant date fair value of the options granted during the six months ended June 30, 2024 was estimated at the date of grant using the Black-Scholes option valuation model. The expected life was estimated using the “simplified” method as defined by the SEC’s Staff Accounting Bulletin 107, Share-Based Payment. The expected volatility was based on the historical volatility of the Company. The risk-free interest rate was based on the continuous rates provided by the U.S. Treasury with a term approximating the expected life of the option. The expected dividend yield was 0% because the Company does not expect to pay any dividends for the foreseeable future. The Company elected the straight-line attribution method in recognizing the grant date fair value of options issued over the requisite service periods of the awards, which are generally the vesting periods. The weighted average grant date fair value for the stock options granted during the six months ended June 30, 2024 was $2.12 per share. During the six months ended June 30, 2025, there were no stock options granted. The assumptions that the Company used to determine the grant-date fair value of stock options granted to employees and directors during the six months ended June 30, 2024 were as follows, presented on a weighted average basis: ​
​ | ​ | ​ | ​
​ | ​ | Six Months Ended June 30, | ​
​ |  | 2024 | ​
​ | ​ | ​ | ​
Expected volatility | ​ | 92.84 | %
Weighted average risk-free interest rate | ​ | 4.00 | %
Expected dividend yield | ​ | 0.00 | %
Expected term (in years) | ​ | 6.44 | ​
​ Stock options generally vest over a three or four year period, as determined by the compensation committee of the Board of Directors at the time of grant. The options expire 10 years from the grant date. As of June 30, 2025, there was approximately $2,205 of unrecognized compensation cost related to non-vested stock options, which is expected to be recognized over a remaining weighted-average period of approximately 1.54 years. Restricted Stock Units (“RSUs”) The Company did not grant any RSUs during the six months ended June 30, 2025 and 2024. The following table presents RSU activity under the 2016 Plan during the six months ended June 30, 2025: ​
​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | Weighted
​ | ​ | ​ | ​ | Average Grant
​ |  | Number of Shares |  | Date Fair Value
Outstanding at December 31, 2024 |  | 220,000 | ​ | $ | 19.40
Vested | ​ | (220,000) | ​ | $ | 19.40
Outstanding at June 30, 2025 |  | — | ​ | $ | —
​ During the six months ended June 30, 2025, 220,000 RSUs vested. As of June 30, 2025, there were no shares outstanding covered by RSUs. The Company recognized stock-based compensation expense related to the issuance of stock option awards and RSUs to employees and non-employees in the condensed consolidated statements of operations during the three and six months ended June 30, 2025 and 2024 as follows: Stock Based Compensation Expense ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three Months Ended June 30, | ​ | Six Months Ended June 30,
​ |  | 2025 |  | 2024 |  | 2025 |  | 2024
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Research and development |  | $ | 387 | ​ | $ | 729 | ​ | $ | 1,021 | ​ | $ | 1,356
General and administrative |  | ​ | 476 | ​ |  | 641 | ​ | ​ | 1,046 | ​ |  | 1,262
Restructuring charges | ​ | ​ | 626 | ​ | ​ | — | ​ | ​ | 626 | ​ | ​ | —
Total | ​ | $ | 1,489 | ​ | $ | 1,370 | ​ | $ | 2,693 | ​ | $ | 2,618
​

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