Prior to the effectiveness of the registration statement on Form S-1 (File No. 333-256838) for its IPO, the Company granted share-based awards under the 2020 Stock Option and Grant Plan, as amended (the “2020 Plan”). The Company was authorized to grant under the 2020 Plan incentive stock options, nonqualified stock options, restricted stock awards, restricted stock units and other share-based awards to the Company’s officers, employees, directors and consultants. Options under the 2020 Plan could be granted for periods of up to 10 years and at prices no less than 100.0% of the estimated fair value of the shares on the date of grant as determined by the Board, provided, however, that the exercise price of an incentive stock option granted to a 10.0% stockholder shall not be less than 110.0% of the estimated fair value of the shares on the date of grant and the option is not exercisable after the expiration of five years from the date of grant. Options generally vest monthly over four years with or without one year cliff vesting. Per the 2020 Plan, granted options may be early exercised prior to vesting and the Company will issue shares of restricted stock upon the early exercise with vesting terms consistent with the original grant. Upon completion of the Company’s IPO, the remaining shares available for issuance under the 2020 Plan were retired, and the Company no longer grants awards pursuant to the 2020 Plan.

In June 2021, the Company’s board of directors approved the 2021 Stock Option and Incentive Plan (the “2021 Plan”) that became effective immediately prior to the date when the Company’s prospectus was declared effective by the SEC on June 24, 2021. The Company initially reserved 5,636,000 shares of common stock for issuance of awards under the 2021 Plan. The 2021 Plan provides that the number of shares reserved and available for issuance under the plan will automatically increase each January 1, beginning on January 1, 2022, by 5% of the outstanding number of shares of the Company’s common stock on the immediately preceding December 31, or such lesser number of shares as determined by the Company’s compensation committee. On January 1, 2022 and 2023, the number of shares of common stock available under the 2021 Plan increased by 2,900,541 shares and 2,911,088 shares, respectively pursuant to this evergreen provision of the 2021 Plan. The option exercise price of each option will be determined by the Company’s compensation committee but generally may not be less than 100% of the fair market value of the Company’s common stock on the date of grant. The term of each option will be fixed by the Company’s compensation committee and may not exceed ten years from the date of grant. The grant date fair value of all awards made under the 2021 Plan and all other cash compensation paid by the Company to any non-employee director for services as a non-employee director in any calendar year may not exceed $1.0 million for the first year of service and $750.0 thousand for each year of service thereafter.

As of March 31, 2023, there were 6,235,813 shares available for future issuance under the 2021 Plan.

During the year ended December 31, 2020, the Company issued 832,983 shares as restricted stock awards under the 2020 Plan. The purchase price of the restricted common stock awards was fair value as determined by the Board at the issuance date. The shares vest monthly over four years with the one-year cliff vesting from the grant date. Upon termination of employment, the Company has the right to repurchase any unvested restricted shares. The repurchase price for unvested shares of common stock will be the lower of (i) the fair market value on the date of repurchase or (ii) their original purchase price. There were no grants of restricted stock awards for the three months ended March 31, 2023 and 2022.

The Company accounted for restricted stock awards as early exercised options and recognized a liability in other liabilities when cash was received for the purchase of shares of restricted stock awards. As shares of restricted stock awards vest, the Company reclassified the liability to common stock and additional paid in capital. As of March 31, 2023 and December 31, 2022, the Company recorded a minimal liability for restricted stock awards included in other liabilities.

There were no shares of restricted stock award shares canceled and repurchased during three months ended March 31, 2023 and 2022. There were 604,734 and 553,443 shares of restricted stock vested as of March 31, 2023 and December 31, 2022, respectively.

In June 2021, the Company’s board of directors and stockholders approved the 2021 Employee Stock Purchase Plan (the “ESPP”) which became effective upon the IPO. Pursuant to the ESPP, certain employees of the Company, excluding consultants and non-employee directors, are eligible to purchase common stock of the Company at a reduced rate during offering periods. The ESPP permits participants to purchase common stock using funds contributed through payroll deductions, subject to a calendar year limit of $25,000 and at a purchase price of 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the applicable purchase date, which will be the final trading day of the applicable purchase period. The ESPP has two annual purchase periods extending from June to November and December to May.

The Company recorded $0.1 million and $0.1 million in accrued liabilities as of March 31, 2023 and December 31, 2022, respectively. There were no shares issued under the ESPP during the three months ended March 31, 2023 and 2022.

Stock options issued under the 2020 Plan and 2021 Plan generally vest over a four-year period and expire ten years from the date of grant. Certain options provide for accelerated vesting if there is a change in control, as defined in the individual award agreements.

A summary of option activity under the 2020 Plan and the 2021 Plan during the three months ended March 31, 2023 is as follows:


	Number of Options			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2022		7,755,303		$	8.47		8.7	$	794
Options granted - 2021 Plan		2,933,350		$	2.18
Options exercised		—		$	—
Options cancelled		(848,226	)	$	7.93
Outstanding as of March 31, 2023		9,840,427		$	6.64		7.8	$	1,212
Exercisable		2,890,823		$	8.53		6.3	$	330
Vested and expected to vest as of March 31, 2023		9,840,427		$	6.64		7.8	$	1,212

Aggregate intrinsic value represents the difference between the fair value of the underlying common stock and the exercise price as of March 31, 2023. The weighted-average grant date fair value of options granted during the three months ended March 31, 2023 was $1.53 per share. There were no stock options exercised during the three months ended March 31, 2023 and 2022, respectively.

The terms of the 2020 Plan permit the exercise of options granted prior to vesting, subject to required approvals. The unvested shares are subject to the repurchase right upon termination of employment at the original purchase price. The repurchase right lapses in 180 days after the termination of the employee’s employment. Shares purchased by employees pursuant to the early exercise of stock options are not deemed, for accounting purposes, to be issued until those shares vest according to their respective vesting schedules. Cash received for early exercised stock options is recorded as other liabilities on the condensed balance sheet and is reclassified to common stock and additional paid-in capital as such shares vest. During the three months ended March 31, 2023, the Company repurchased 26,942 shares that were previously early exercised. No shares were repurchased during the three months ended March 31, 2022.

As of March 31, 2023 and December 31, 2022, 391,928 and 554,695 shares, respectively, remained subject to the right of repurchase as a result of the early exercised stock options. The remaining liability related to early exercised shares as of March 31, 2023 and December 31, 2022 was $0.1 million and $0.1 million, respectively, and was recorded within accrued expenses and other liabilities on the Company’s condensed balance sheets.

The following table presents the components of stock-based compensation expense for the Company’s stock-based awards for the periods presented (in thousands):


	Three Months Ended March 31,
	2023		2022
Restricted stock awards and founders’ common stock awards	$	2	$	2
ESPP		109		146
Stock options		3,152		3,194
Total stock-based compensation expense	$	3,263	$	3,342

The above stock-based compensation expense also includes the expenses of $0.4 million related to stock options issued to non-employees during the three months ended March 31, 2023. There was no stock-based compensation expense for options issued to non-employees during the three months ended March 31, 2022.

The following table presents the classification of stock-based compensation expense for the Company’s stock-based awards for the periods presented (in thousands):


	Three Months Ended March 31,
	2023		2022
Research and development expenses	$	1,120	$	1,373
General and administrative expenses		2,143		1,969
Total stock-based compensation expense	$	3,263	$	3,342

As of March 31, 2023 and December 31, 2022 there was $27.5 million and $31.0 million of unrecognized stock-based compensation expense related to the employee and non-employee awards, which is expected to be recognized over a weighted-average period of 2.9 and 2.6 years, respectively.