Stock-based Compensation | 11. Stock-based Compensation In October 2020, the Company’s shareholders approved the Company’s 2020 Incentive Award Plan (“2020 Plan”). The 2020 Plan initially provided for the issuance of up to 7,924,000 shares of common stock and for the grant of incentive stock options or other incentive awards to employees, officers, directors and consultants of the Company. The number of shares of common stock that may be issued under the 2020 Plan is also subject to increase on the first day of each calendar year equal to the lesser of i) 5 % of the aggregate number of shares of common stock outstanding on the final day of the immediately preceding calendar year or ii) such smaller number of shares as is determined by the board of directors. Through December 31, 2023, the shares available under the plan were increased by 12,450,364 shares. As of December 31, 2023, 6,510,704 shares of common stock were available for future issuance under the 2020 Plan. In January 2024, the shares of the Company's common stock available under the 2020 Plan were increased by 4,171,775 shares. The 2020 Plan replaced and is the successor of the Company’s 2013 Equity Incentive Plan, as amended (“2013 Plan”). In the event of any cancellation of an outstanding option award under the 2013 Plan, the shares underlying the cancelled option award will be made available for grant under the 2020 Plan. Restricted Stock Units During the year ended December 31, 2023 and 2022, respectively, the Company granted 2,264,700 and 182,350 restricted stock units to employees with an aggregate grant date fair market value of $ 10,384 and $ 1,302 . The restricted stock unit awards vest in three annual installments. In January 2023, the Company issued 53,935 shares of common stock upon the vesting and settlement of restricted stock units. During the year ended December 31, 2023 and 2022, 34,998 and 20,600 restricted stock units were cancelled due to employee terminations. Number of Weighted Average Outstanding at January 1, 2023 161,750 $ 7.14 Granted 2,264,700 $ 4.59 Released ( 53,935 ) $ 7.14 Cancelled ( 34,998 ) $ 5.42 Unvested shares at December 31, 2023 2,337,517 $ 4.69 Performance-based Restricted Stock Units No performance-based restricted stock units were granted during the year ended December 31, 2023. During the year ended December 31, 2022, the Company granted 742,070 performance-based restricted stock units to employees with an aggregate grant date fair value of $ 5,298 . No performance-based restricted stock units were granted during the year ended December 31, 2023. The performance stock unit awards provide for a performance period from February 1, 2022 through January 31, 2025 to achieve up to six defined performance metrics. The percentage of each award eligible to vest will be determined based on the number of metrics achieved during the performance period and may range from 0 % to 200 %. The Company has not recognized any compensation expense through December 31, 2023, as the minimum performance criteria had not been deemed probable. The vesting of any eligible awards will occur in equal installments on January 31, 2025 and January 31, 2026. During the year ended December 31, 2023, there were no cancellations of performance-based restricted stock units. During the year ended December 31, 2022, 17,100 performance-based restricted stock units were cancelled due to employee terminations. Number of Weighted Average Outstanding at January 1, 2023 724,970 $ 7.14 Granted — $ — Release — $ — Cancelled — $ — Unvested shares at December 31, 2023 724,970 $ 7.14 Stock Options The following summarizes stock option activity: Number of Weighted Weighted Aggregate Outstanding at January 1, 2023 13,632,278 $ 18.48 7.7 $ 10,937 Granted 3,777,550 $ 4.48 Exercised — $ — Cancelled ( 392,509 ) $ 21.46 Outstanding at December 31, 2023 17,017,319 $ 15.30 7.1 $ 5,080 Vested and expected to vest at December 31, 2023 17,017,319 $ 15.30 7.1 $ 5,080 Vested and exercisable at December 31, 2023 11,084,169 $ 16.46 6.4 $ 5,078 The aggregate intrinsic value of options granted is calculated as the difference between the exercise price of the options and the estimated fair value of the Company’s common stock for those options that had exercise prices lower than the fair value of the Company’s common stock. Option grants generally vest over a service period of three or four years and have a contractual term of ten years . As of December 31, 2023, total unrecognized compensation expense related to stock option awards was $ 55,157 , which amount is being recognized over a remaining weighted average period of 2.2 years. The weighted average grant date fair value per option granted during the years ended December 31, 2023 and 2022 was $ 3.27 and $ 5.09 , respectively. The fair value of each award was estimated using Black-Scholes based on the following assumptions: For the Year Ended 2023 2022 Risk-free interest rate 3.65 % 2.10 % Expected term 5.97 years 5.96 years Expected volatility 85.0 % 85.0 % Expected dividend yield 0 % 0 % Employee Stock Purchase Plan In October 2020, the Company’s shareholders approved the ESPP, which became effective upon the closing of the Company’s IPO in November 2020. The Company initially reserved a total of 1,187,000 shares of its common stock for issuance under the ESPP. The ESPP provides that the number of shares reserved and available for issuance under the ESPP will be increased on January 1 of each calendar year by 1 % of the number of shares of the Company's common stock issued and outstanding on the immediately preceding December 31 or such lesser amount as specified by the board of directors. Through December 31, 2022, there was no increase in the number of shares reserved for issuance under the ESPP. In January 2024 and 2023, the number of shares of the Company's common stock available for issuance under the ESPP was increased by 834,355 and 832,876 shares, respectively. The Company issued 93,939 and 29,036 shares for proceeds of $ 257 and $ 140 during the years ended December 31, 2023 and 2022, respectively. Stock-based Compensation Expense Stock-based compensation expense is classified as follows: For the Year Ended 2023 2022 Research and development expense $ 22,666 $ 21,870 General and administrative 26,762 24,848 Total stock-based compensation expense $ 49,428 $ 46,718 The components of stock-based compensation expense were: For the Year Ended 2023 2022 Restricted stock units $ 3,679 $ 352 Performance-based restricted stock units — — Stock options 45,626 46,220 ESPP 123 146 Total stock-based compensation expense $ 49,428 $ 46,718 |