On July 23, 2021, the Company’s board of directors adopted and its stockholders approved the 2021 Stock Option and Incentive Plan (the “2021 Plan”), which became effective on July 28, 2021. The 2021 Plan provides for the grant of incentive stock options, non-qualified stock options, stock appreciation rights, restricted stock awards, restricted stock units, unrestricted stock awards, cash-based awards and dividend equivalent rights. The number of shares of Class A common stock reserved for issuance under the 2021 Plan shall be increased on each January 1 by 5.0% of the number of shares of the Company’s Class A and Class B common stock outstanding on the immediately preceding December 31 or such lesser number of shares determined by the Company’s board of directors or compensation committee of the board of directors. The number of shares of Class A common stock reserved for issuance was increased by 2,833,447 shares effective as of January 1, 2023, in accordance with the provisions of the 2021 Plan described above. The shares of Class A common stock underlying any awards 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, expired or are otherwise terminated (other than by exercise) under the 2021 Plan and the Company’s previously outstanding 2017 Stock Option and Grant Plan will be added back to the shares of Class A common stock available under the 2021 Plan. As of March 31, 2023, 6,360,795 shares of Class A common stock remained available for future issuance under the 2021 Plan.

On July 23, 2021, the Company’s board of directors adopted and its stockholders approved the 2021 Employee Stock Purchase Plan, which became effective on July 28, 2021. The Company’s board of directors approved the amendment and restatement of the 2021 Employee Stock Purchase Plan in its entirety on June 16, 2022 (as amended and restated, the “ESPP”). The ESPP permits eligible employees to purchase shares of Class A common stock at a discount and consists of consecutive, overlapping 12-month offering periods, each consisting of two six-month purchase periods beginning in December and June. On the first day of each offering period, the Company will grant to each employee who is enrolled in the ESPP an option to purchase up to a whole number of shares of Class A common stock. The purchase price of each of the shares purchased in a given purchase period will be 85% of the closing price of a share of the Class A common stock on the first day of the offering period or the last day of the purchase period, whichever is lower. The number of shares of Class A common stock that may be issued under the ESPP will automatically increase on each January through January 1, 2031, by the least of (i) 473,064 shares of Class A common stock, (ii) 1% of the number of shares of the Company’s Class A and Class B common stock outstanding on the immediately preceding December 31 or (iii) such lesser number of shares as determined by the administrator of the ESPP.

The initial offering period of the ESPP commenced on December 1, 2022. The number of shares of Class A common stock reserved for issuance was increased by 473,064 shares effective as of January 1, 2023, in accordance with the provisions of the ESPP described above. During the three months ended March 31, 2023, no shares were sold under the ESPP, and as of March 31, 2023, 1,419,192 shares remained available for issuance and sale.

During the three months ended March 31, 2023 the Company granted options to its employees and directors with service-based vesting for the purchase of an aggregate of 2,134,430 shares of Class A common stock with a total grant-date fair value of $41.7 million.

The Company recorded stock-based compensation expense related to common stock options and restricted common stock in the following expense categories of its consolidated statements of operations and comprehensive loss (in thousands):


	Three Months Ended March 31,
	2023		2022
Research and development expenses	$	2,513	$	947
General and administrative expenses		2,858		1,258
	$	5,371	$	2,205

As of March 31, 2023, total unrecognized compensation cost related to common stock options was $67.1 million, which is expected to be recognized over a weighted average period of 3.2 years.