The 2018 Equity Incentive Plan, or 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, or the 2021 Plan, which became effective on June 16, 2021. The 2021 Plan provides for grant of qualified and nonqualified 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. Under the 2021 Plan, the number of shares of common stock initially reserved for issuance was the sum of: (1) 3,466,530; plus (2) the number of shares as was equal to the sum of (x) the number of shares of common stock reserved for issuance under the 2018 Plan that remained available for grant under the 2018 Plan on June 16, 2021 and (y) the number of shares of common stock subject to outstanding awards granted under the 2018 Plan that expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right; plus (3) an annual increase, to be added on the first day of each fiscal year, commencing on January 1, 2022 and continuing until, and including, January 1, 2031, equal to the lesser of (i) 5% of the number of shares of common stock outstanding on such date and (ii) the number of shares of common stock determined by the Company’s board of directors.

On January 1, 2022, 2,425,587 shares of the Company's common stock were added to the amount reserved for issuance under the 2021 Plan in accordance with the 2021 Plan described above. As of June 30, 2022, the Company had reserved 7,057,629 shares of the Company's common stock for issuance of equity awards, of which 3,456,180 shares 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.

Stock-based compensation expense recorded in the condensed consolidated statements of operations and comprehensive loss is as follows:


	Three months ended June 30,				Six months ended June 30,
(in thousands)	2022		2021		2022		2021
Research and development	$	2,955	$	708	$	5,421	$	1,021
General and administrative		2,694		643		4,432		1,000
Total stock-based compensation expense	$	5,649	$	1,351	$	9,853	$	2,021

The following table provides a summary of stock option activity during the six months ended June 30, 2022:


	Number of options			Weighted average exercise price per share		Weighted average remaining contractual life (in years)		Aggregate intrinsic value(2) (in thousands)
Outstanding at December 31, 2021		6,119,295		$	9.44
Granted		2,103,350			27.34
Exercised		(172,699	)		3.62
Forfeited		(164,729	)		25.77
Outstanding at June 30, 2022		7,885,217		$	14.09		8.5	$	52,868
Exercisable at June 30, 2022		2,301,148		$	4.40		7.8	$	25,676
Expected to vest after June 30, 2022(1)		5,584,069		$	18.08		8.8	$	27,192

(1)

This represents the number of unvested options outstanding as of June 30, 2022 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 June 30, 2022.

As of June 30, 2022, there was $66.3 million of unrecognized compensation cost related to unvested stock options, which is expected to be recognized over a weighted-average period of approximately 2.8 years.

During the six months ended June 30, 2022, the Company granted 524,875 restricted stock units under the 2021 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 June 30, 2022 was as follows:


	Shares			Weighted- average grant date fair value per share
Unvested restricted stock units as of December 31, 2021		32,000		$	36.58
Restricted stock units granted		524,875		$	20.48
Restricted stock units forfeited		(4,500	)	$	30.94
Unvested restricted stock units as of June 30, 2022		552,375		$	21.33

As of June 30, 2022, there was $11.0 million of unrecognized 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 3.9 years.

In June 2021, the board of directors adopted, and the Company's stockholders approved, the 2021 Employee Stock Purchase Plan, or the ESPP, as amended and restated, which became effective on June 16, 2021. The Company initially reserved 433,316 shares of common stock for sale under the ESPP. The aggregate number of shares reserved for sale under the ESPP increases automatically on the first day of each fiscal year commencing on January 1, 2022 through January 1, 2031, by the number of shares equal to the least of (a) 1,083,290 shares, (b) 1% of the total outstanding shares of common stock on such date, and (c) a number of shares as may be determined by the board of directors in any particular year. The first offering period under the ESPP commenced on June 16, 2021 and ended on December 13, 2021. On January 1, 2022, 485,117 shares of common stock were added to the amount reserved for sale under the ESPP. As of June 30, 2022, 844,918 shares remained available for issuance under the ESPP. The second offering period ended on May 31, 2022, for which offering period the Company issued 25,218 shares. The next offering period commenced on June 1, 2022 and will end on November 30, 2022.