Stock-Based Compensation | 8. Stock-Based Compensation 2019 Stock Incentive Plan The Company's 2019 Stock Incentive Plan, or the 2019 Plan, provided for the Company to grant incentive stock options, stock appreciation rights, restricted stock, restricted stock units, and other stock-based awards. The 2019 Plan was administered by the Board or, at the discretion of the Board, by a committee delegated by Board. The exercise prices, vesting and other restrictions were determined at the discretion of the Board, or its committee if so delegated. The Company’s Board valued the Company’s common stock, taking into consideration its most recently available valuation of common stock performed by third party valuation specialists as well as additional factors which may have changed since the date of the most recent contemporaneous valuation through the date of grant. The total number of shares of common stock that could have been issued under the 2019 Plan was 5,317,559 shares, of which 474,951 shares remained available for grant on September 19, 2022, the date that the Company's 2022 Equity Incentive Plan, or the 2022 Plan, became effective. Upon the effectiveness of the 2022 Plan, the 474,951 remaining shares available under the 2019 Plan were transferred and became available for issuance under the 2022 Plan. Shares of common stock underlying outstanding awards under the 2019 Plan that are forfeited, cancelled, held back upon exercise or settlement of an award to satisfy the exercise price or tax withholding, reacquired by the Company prior to vesting, satisfied without the issuance of stock, expire or are otherwise terminated (other than by exercise) will be added to the shares of common stock available for issuance under the 2022 Plan. 2022 Plan The 2022 Plan was approved by the Board and stockholders in August 2022. The 2022 Plan became effective on September 14, 2022 and replaced the Company's 2019 Plan on that date. The 2022 Plan authorizes the award of incentive stock options, or ISOs, non-qualified stock options, or NQSOs, Restricted Stock Awards, or RSAs, Stock Appreciation Rights, or SARs, Restricted Stock Units, or RSUs, performance awards and stock bonus awards. Pursuant to the 2022 Plan, ISOs may be granted only to employees. The number of shares initially reserved for issuance under the 2022 Plan is 4,901,688 shares of common stock, which includes the 474,951 shares transferred from the 2019 Plan, and shall automatically increase on January 1 of each of 2023 through 2032 by the number of shares equal of the lesser of 5 % of the aggregate number of shares of all classes of the common stock, plus the total number of shares of common stock issuable upon conversion of any preferred stock (if any) or exercise of any pre-funded warrants, as issued and outstanding as of the immediately preceding December 31, or a number as may be determined by the Board. The 2022 Plan is administered by the Board or, at the discretion of the Board, by a committee of the Board. The exercise prices, vesting and other restrictions are determined at the discretion of the Board, or its committee if so delegated, except that the exercise price per share of stock options may not be less than 100 % of the fair market value of the share of common stock on the date of grant and the term of stock option may not be greater than ten years . Shares that are expired terminated, surrendered or cancelled under the 2022 Plan without having been fully exercised will be available for future awards. Stock Options The assumptions that the Company used to determine the grant-date fair value of stock options awarded to employees, were as follows for the three and six months ended June 30, 2022 and 2023: Six Months Ended June 30, 2022 2023 Expected term (in years) 5.71 - 6.53 5.21 - 6.96 Expected volatility 81.9 - 82.7 % 85.7 - 88.2 % Risk-free interest rate 1.70 - 2.56 % 3.6 - 4.2 % Expected dividend yield — — The following table summarizes the Company’s stock option activity since December 31, 2022: Number of Shares Weighted-Average Weighted-Average Aggregate Intrinsic Outstanding as of December 31, 2022 3,644,500 $ 10.45 9.51 $ 1,283 Granted 1,561,840 4.27 Exercised ( 37,268 ) 1.57 Forfeited or cancelled ( 158,323 ) 3.51 Outstanding as of June 30, 2023 5,010,749 4.09 9.15 3,758 Options vested and exercisable as of June 30, 2023 984,275 3.85 8.83 1,005 Options unvested as of June 30, 2023 4,026,474 4.15 9.22 2,753 The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock. The weighted-average grant-date fair value per share of stock options granted during the six months ended June 30, 2023 was $ 3.17 . As of June 30, 2023, there was $ 25.5 million of unrecognized stock-based compensation expense related to unvested stock options, to be recognized over a weighted-average period of 3.00 years. The total fair value of options vested during the six months ended June 30, 2023 was $ 3.5 million. Repricing of Stock Options On March 6, 2023, the Board approved the reduction in exercise price of certain options that had been granted under the 2019 Plan and the 2022 Plan, that have an exercise price greater than or equal to $ 8.61 per share, which were each repriced at an exercise price of $ 4.20 effective March 21, 2023. There were no changes in the vesting schedule or maturity term of the options. Options representing 3,085,468 underlying shares were included in this repricing and the total incremental stock-based compensation expense associated with the modification of these options was $ 2.1 million. The incremental expense as a result of the repricing was recognized immediately for vested awards, and the incremental expense for the unvested awards will be recognized over the remaining requisite service period. Restricted Common Stock Awards The Company has granted restricted common stock awards with service and performance and service based vesting conditions to employees of the Company. Unvested shares of restricted common stock may not be sold or transferred by the holder, except for transfers for estate planning purposes in which the transferee agrees to remain bound by all restrictions set forth in the original common stock purchase agreement. These restrictions lapse over the vesting term of each award, which is typically four years . The purchase price of each share of restricted common stock was $ 0.0001 per share. On August 9, 2021, the Company’s chief executive office, or CEO, purchased 1,218,836 shares of common stock at a purchase price of $ 1.44 per share, under the terms of a restricted common stock award granted under the 2019 Plan. These shares were purchased in exchange for a promissory note, or the Promissory Note, of $ 1.8 million. The shares granted include both service and performance-based vesting criteria and accrued at an interest rate of 0.76 % per annum, compounded annually and were accounted for as restricted stock. On August 22, 2022, the Company forgave the entire promissory note, including principal and accrued and unpaid interest. As a result this is considered a modification to the original awards, and the Company recognized the grant date fair value plus any incremental fair value due to the modification. The incremental cost was measured as the difference between the fair value of the award at modification date and the fair value of the original award immediately prior to modification. As a result of accounting for the modification, the Company recorded an incremental stock-based compensation charge of $ 1.0 million, which will be recognized over the remaining requisite service period of award from the date of the modification. The CEO was paid a one-time special bonus of $ 1.9 million to offset the CEO’s tax liability as a result of the forgiveness of the promissory note, or the Tax Payment, which is subject to a three-year vesting schedule with six-month cliffs . The Company is allowed to claw-back the unvested portion of the Tax Payment in the event that the CEO’s employment is terminated before the end of the three-year vesting period, provided that the CEO’s employment is terminated by the Company other than for cause, or if the CEO resigns for a good reason (a) within 12 months following a change of control, or (b) within 3 months preceding a change in control but as to only if the separation occurs after a potential change in control. In the event the CEO’s employment is terminated, the unvested portion of the Tax Payment will accelerate and will not be subject to the claw back provision. The claw-back provision will be accounted for if and when the CEO leaves under the relevant circumstances and the payment amount will be capitalized and recognized over the related service period as G&A employee salary expense. A summary of the activity of the restricted common stock since December 31, 2022: Number of Shares Weighted-Average Unvested at December 31, 2022 964,992 $ 1.34 Granted — — Vested ( 214,274 ) 1.22 Cancelled or forfeited — — Unvested at June 30, 2023 750,718 $ 1.37 No restricted common stock awards were granted during the six months ended June 30, 2023. Stock-Based Compensation Expense Stock-based compensation expense included in the Company’s condensed consolidated statements of operations was as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2022 2023 2022 2023 Research and development $ 234 $ 1,055 $ 381 $ 2,073 General and administrative 925 1,790 1,228 3,454 Total stock-based compensation expense $ 1,159 $ 2,845 $ 1,609 $ 5,527 |