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Equity Incentive Plans | 12 Months Ended
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Dec. 31, 2024
Equity Incentive Plans |
Equity Incentive Plans | 10. Equity Incentive Plans Stock Award Plans ​ The Company maintains a 2016 Equity Incentive Plan (the “2016 Plan”), which provides for the issuance of incentive share awards in the form of non-qualified and incentive stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards and performance-based stock awards. The awards may be granted by the Company’s Board of Directors to its employees, directors and officers and to consultants. The term of the options granted is ten years, the exercise price is the Company’s closing price at the date of grant and the vesting period is usually four years. The Company also granted RSUs under the 2016 Plan that vest over four years. Under the 2016 Plan, the number of shares authorized for issuance is automatically increased by a number equal to 5% of the total number of shares of the Company’s capital stock outstanding on December 31st of the preceding calendar year, or a lesser number of shares determined by the Board of Directors annually beginning from January 1, 2017 until January 1, 2026. As of December 31, 2024, there were 3,405,908 shares available for issuance under the 2016 Plan. The Company has issued restricted stock awards RSAs under certain legacy option plans that generally vested two to four years based on service conditions. As of December 31, 2024, all RSAs were fully vested. Pursuant to its 2016 Employee Stock Purchase Plan (“ESPP”), the Company may grant or provide for the grant of rights to purchase shares of its Common Stock. The number of shares of its Common Stock reserved for issuance under the ESPP will automatically increase on January 1st of each calendar year by the lesser of 1% of the total number of shares of the Company’s Common Stock outstanding on December 31st of the preceding calendar year and 30,000 shares, subject to the ability of the Company’s Board of Directors to take action to reduce the size of the increase in any given year. There were no awards issued under ESPP. As of December 31, 2024, the Company had reserved 11,890 shares for future grants under the ESPP. ​ Stock option activities during the year ended December 31, 2024 are presented below: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Options Outstanding
​ | ​ | ​ | ​ | ​ | ​ | ​ | Weighted | ​ | ​ | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | Average | ​ | ​ | ​
​ | ​ | ​ | ​ | Weighted | ​ | Remaining | ​ | ​ | ​
​ | ​ | ​ | ​ | Average | ​ | Contractual | ​ | Aggregate
​ | ​ | ​ | ​ | Exercise | ​ | Term | ​ | Intrinsic
​ |  | Shares |  | Price |  | (Years) |  | Value (in thousands)
Outstanding at December 31, 2023 |  | 3,165,216 | ​ | $ | 5.04 |  | 5.9 | ​ | $ | 429
Granted |  | 1,859,054 | ​ | $ | 3.34 |  | ​ |  | $ | —
Exercised | ​ | (37,282) | ​ | $ | 3.38 | ​ | ​ | ​ | $ | 24
Forfeited/Cancelled/Expired |  | (1,231,023) | ​ | $ | 6.48 |  | ​ |  | $ | 4
Outstanding at December 31, 2024 |  | 3,755,965 | ​ | $ | 3.74 |  | 7.5 | ​ | $ | 4
Vested and expected to vest at December 31, 2024 |  | 3,755,965 | ​ | $ | 3.74 |  | 7.5 | ​ | $ | 4
Exercisable at December 31, 2024 |  | 2,059,396 | ​ | $ | 4.04 |  | 6.4 | ​ | $ | 2
​ The aggregate intrinsic value of options at December 31, 2024 is based on the Company’s closing stock price on that date of $1.85 per share. ​ The weighted average grant date fair value of the options granted during 2024 and 2023 was $2.54 and $1.97, respectively. The fair value of vested options during the year ended December 31, 2024 and 2023 was $2.8 million and $5.1 million, respectively. ​ ​ Restricted stock awards and restricted stock unit award activities during the year ended December 31, 2024 are presented below: ​
​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | Weighted Avg
​ | ​ | ​ | ​ | Grant Date
​ |  | Shares |  | Fair Value
Outstanding at December 31, 2023 | ​ | 200,000 | ​ | $ | 2.39
Granted | ​ | 90,000 | ​ | $ | 3.38
Vested | ​ | (50,000) | ​ | $ | 2.39
Cancelled | ​ | (20,000) | ​ | $ | 3.38
Outstanding at December 31, 2024 | ​ | 220,000 | ​ | $ | 2.73
​ As of December 31, 2024, there was $2.6 million of total unrecognized compensation expense related to unvested stock options and restricted stock units, which the Company expects to recognize over the weighted average remaining period of approximately 1.9 years. ​ ​ Stock-based Compensation ​ The Company estimates the fair value of stock options with performance and service conditions using the Black-Scholes valuation model. ​ The assumptions used to estimate the options fair value were as follows: ​
​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
​ |  | 2024 |  | 2023
Risk-free interest rate | ​ | 3.54%-4.25% | ​ | 3.54%-5.54%
Expected volatility | ​ | 89.40%-92.50% | ​ | 75.40%-116.96%
Expected term (in years) | ​ | 5.1-7.0 | ​ | 0.1-7.0
Expected dividend yield | ​ | 0% | ​ | 0%
​ The tables below summarize the total stock-based compensation expense (reversal) included in the Company’s consolidated statements of operations for the periods presented (in thousands): ​ ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Year Ended December 31,
​ |  | 2024 |  | 2023
Research and development | ​ | $ | 663 | ​ | $ | 1,013
General and administrative | ​ |  | 2,230 | ​ |  | (75)
Total stock-based compensation | ​ | $ | 2,893 | ​ | $ | 938
​

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