Stock-based compensation | 11. Stock-based compensation The 2018 Equity Incentive Plan (the “2018 Plan”), adopted by the board of directors in August 2018 provided for the grant of qualified incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock and restricted stock units to the Company’s employees, officers, directors, advisors, and outside consultants for the issuance or purchase of shares of the Company’s common stock. The maximum number of shares of common stock that were authorized for issuance under the 2018 Plan was 6,885,653 . In June 2021, the Company's board of directors adopted, and the Company's stockholders approved, the 2021 Stock Incentive Plan (the “2021 Plan”), which became effective on June 16, 2021. The 2021 Plan provides for the grant of incentive stock options and nonstatutory stock options, stock appreciation rights, restricted and unrestricted stock and stock units, performance awards, and other share-based awards to the Company's employees, directors, advisors and outside consultants. The shares reserved for issuance pursuant to the 2021 Plan are subject to an annual increase through January 1, 2031. On January 1, 2024, 4,098,485 shares of the Company's common stock were added to the amount reserved for issuance under the 2021 Plan. As of March 31, 2024, the Company had reserved 14,242,655 shares of the Company's common stock for issuance of stock options, restricted stock, and restricted stock units, of which 3,731,207 remained available for future grant under the 2021 Plan. Upon effectiveness of the 2021 Plan, the Company ceased granting additional awards under the 2018 Plan. In February 2024, the board of directors adopted the 2024 Inducement Stock Incentive Plan (the “Inducement Plan”). The Inducement Plan provides for the grant of nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards to persons who (a) were not previously an employee or director or (b) are commencing employment with the Company following a bona fide period of non-employment, in either case, as an inducement material to such person’s entry into employment with the Company and in accordance with the requirements of the Nasdaq Stock Market Rule 5635(c)(4). As of March 31, 2024, the Company had reserved 4,000,000 shares of the Company’s common stock for issuance of nonstatutory stock options and restricted stock unit awards, of which 3,846,700 remained available for future grant under the Inducement Plan. Stock-based compensation expense recorded in the Company's condensed consolidated statements of operations and comprehensive loss is as follows : Three months ended March 31, (in thousands) 2024 2023 Research and development $ 5,625 $ 4,489 General and administrative 4,716 3,535 Total stock-based compensation expense $ 10,341 $ 8,024 Stock options The following table provides a summary of stock option activity during the three months ended March 31, 2024: Number of Weighted Weighted Aggregate (2) Outstanding at December 31, 2023 9,924,878 $ 16.98 Granted 2,639,100 12.76 Exercised ( 76,044 ) 3.95 Forfeited ( 140,987 ) 22.03 Outstanding at March 31, 2024 12,346,947 $ 16.10 8.1 $ 34,374 Exercisable at March 31, 2024 5,412,030 $ 13.77 6.9 $ 28,776 Expected to vest after March 31, 2024(1) 6,934,917 $ 17.91 9.0 $ 5,598 (1) This represents the number of unvested options outstanding as of March 31, 2024 that are expected to vest in the future. (2) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the fair value of the common stock for the options that were in the money as of March 31, 2024 . As of March 31, 2024, there was $ 82.4 million of u nrecognized stock-based compensation expense related to unvested stock options, which is expected to be recognized over a weighted-average period of approximately 2.8 years. Restricted stock units During the three months ended March 31, 2024, the Company granted 1,179,470 restricted stock units under the 2021 Plan and Inducement Plan. These restricted stock units vest annually over a four-year period. A summary of the status of and change in unvested restricted stock units as of March 31, 2024 was as follows: Shares Weighted- Unvested restricted stock units as of December 31, 2023 964,511 $ 19.92 Restricted stock units granted 1,179,470 $ 12.78 Restricted stock units vested ( 7,290 ) $ 32.86 Restricted stock units forfeited ( 33,033 ) $ 19.80 Unvested restricted stock units as of March 31, 2024 2,103,658 $ 15.88 As of March 31, 2024, there was $ 28.9 million of u nrecognized stock-based compensation expense related to restricted stock units that are expected to vest. These costs are expected to be recognized over a weighted-average remaining vesting period of approximately 3.5 years . 2021 Amended and Restated Employee Stock Purchase Plan In June 2021, the board of directors adopted, and the Company's stockholders approved, the 2021 Employee Stock Purchase Plan, (the "ESPP"), as amended and restated, which became effective on June 16, 2021. The shares reserved for issuance pursuant to the ESPP are subject to an annual increase through January 1, 2031. On January 1, 2024, 819,697 shares of common stock were added to the amount reserved for sale under the ESPP . As of March 31, 2024, 2,096,889 shares remained available for issuance under the ESPP. |