Equity-based Compensation and Equity Incentive Plans | ( 8 ) Equity‑based Compensation and Equity Incentive Plans Equity Plans The Company currently has three active equity plans. Pursuant to the evergreen provision of the 2015 Equity Incentive Award Plan (the 2015 Plan), which allows for an annual increase in the number of shares of common stock available for issuance, the Company added 1,909,163 shares to the 2015 Plan on January 1, 2021. Pursuant to the evergreen provision of the 2015 Employee Stock Purchase Plan (ESPP), which allows for an annual increase in the number of shares of common stock available for issuance, the Company added 381,832 shares to the ESPP on January 1, 2021. There were 23,592 options exercised to purchase shares of common stock under the ESPP during the three months ended September 30, 2021 and 42,653 options were exercised during the nine months ended September 30, 2021. As of September 30, 2021, there were an aggregate of 1,642,944 shares available for future grant under the 2017 Stock Incentive Plan (the 2017 Plan) and the 2015 Plan, and 684,841 shares available for future grant under the ESPP. For a full description of the Company’s equity plans, refer to Note 9, Equity-based Compensation and Equity Incentive Plans Stock Options The following table summarizes stock option activity during the nine months ended September 30, 2021. Stock options outstanding Weighted average Weighted remaining Aggregate average contractual intrinsic Number of exercise term value (a) options price (in years) (in thousands) Outstanding at December 31, 2020 3,343,836 $ 6.00 8.4 $ 399 Granted 2,009,796 3.46 Exercised (135,684 ) 2.26 Cancelled/Forfeited (680,330 ) 4.41 Outstanding at September 30, 2021 4,537,618 5.23 8.4 1,444 Vested or expected to vest at September 30, 2021 4,537,618 5.23 8.4 $ 1,444 Exercisable at September 30, 2021 1,866,393 7.70 7.4 $ 554 (a) The aggregate intrinsic value is calculated as the difference between the exercise price of the options and the fair market value of the underlying common stock for the options that were in the money at September 30, 2021 and December 31, 2020. 1,399,443 and 970,826 options were in the money at September 30, 2021 and December 31, 2020, respectively. As of September 30, 2021, there was $6.0 million of unrecognized share-based compensation related to unvested stock option grants which is expected to be recognized over a weighted average period of 2.7 years. The total unrecognized share-based compensation cost will be adjusted for actual forfeitures as they occur. Restricted Common Stock The following table shows restricted stock activity during the nine months ended September 30, 2021: Restricted stock awards Weighted average grant date Number of fair value shares (per share) Unvested at December 31, 2020 478,207 $ 2.19 Granted 242,454 3.50 Vested (343,619 ) 2.39 Forfeited (65,009 ) 2.85 Unvested at September 30, 2021 312,033 $ 2.86 As of September 30, 2021, there was approximately $0.8 million of unrecognized share-based compensation related to restricted stock awards granted, which is expected to be recognized over a weighted average period of 3.3 years. The total unrecognized share-based compensation cost will be adjusted for actual forfeitures as they occur. Employee Stock Purchase Plan The ESPP is considered a compensatory plan with the related compensation cost expensed over the six-month offering periods. The compensation cost for the three and nine months ended September 30, 2021 was $14,000 and $34,000, respectively. The compensation expense related to the ESPP for the three and nine months ended September 30, 2020 was $6,000 and $18,000, respectively. Equity Compensation The Company has recorded total equity-based compensation expense of approximately $0.8 million and $2.6 million during the three and nine months ended September 30, 2021, respectively, and $0.9 million and $3.1 million during the three and nine months ended September 30, 2020, respectively. The following table summarizes equity‑based compensation expense within the Company’s consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2021 and 2020 (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Research and development $ 319 $ 422 $ 1,093 $ 1,349 General and administrative 489 513 1,468 1,756 $ 808 $ 935 $ 2,561 $ 3,105 The following table summarizes equity‑based compensation expense by type of award for the three and nine months ended September 30, 2021 and 2020 (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Stock options $ 744 $ 764 $ 2,243 $ 2,529 Restricted stock awards 50 165 284 558 Employee stock purchase plan 14 6 34 18 $ 808 $ 935 $ 2,561 $ 3,105 |