As of June 30, 2022, the Company has granted service-based awards, which vest over a defined period of service. Most service-based awards vest over a four-year period, with the first 25% vesting following 12 months of continued employment or service, and the remainder vesting in 12 quarterly installments over the following three years. The Company has also granted service-based awards, which vest over a two-year period, with the first 50% vesting following 12 months of continued employment or service, and the remainder vesting in four quarterly installments over the following year.

The 2020 Stock Option and Incentive Plan (the "2020 Plan") became effective in October 2020. The 2020 Plan provides for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock units, and other stock-based awards. The number of shares of the Company’s common stock initially reserved for issuance under the 2020 Plan was 1,043,402 shares. The number of shares reserved shall be annually increased on the first day of each calendar year beginning on January 1, 2021 and ending on and including January 1, 2030, equal to the lesser of 5% of the number of shares of common stock outstanding on the final day of the immediately preceding calendar year or such lesser number of shares determined by the compensation committee. As of January 1, 2022, 1,119,192 additional shares of common stock were reserved for issuance under the 2020 Plan.

The shares of the Company’s common stock subject to outstanding awards under the 2015 Stock Option and Grant 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 will be added back to the shares of common stock available for issuance under the 2020 Plan. As of June 30, 2022, there were 1,084,105 shares available for future issuance under the 2020 Plan.

The Company’s stock options expire after approximately ten years from the date of grant. As of June 30, 2022, the Company does not hold any treasury shares. Upon stock option exercise, the Company issues new shares and delivers them to the participant.

The Company’s 2020 Employee Stock Purchase Plan, (the "ESPP") was adopted by our board of directors, approved by the Company’s stockholders and became effective in October 2020. The ESPP initially provides participating employees with the opportunity to purchase up to an aggregate of 208,680 shares of the Company’s common stock. The number of shares of common stock reserved for issuance under the ESPP may be increased on the first day of each calendar year, beginning on January 1, 2021 and ending on January 1, 2030, by the lesser of (i) 834,720 shares of common stock, (ii) 0.5% of the outstanding shares of common stock on the immediately preceding December 31st or (iii) such lesser number of shares as determined by the administrator of the ESPP. There had been no increase in the number of shares of common stock reserved for issuance under the ESPP as of June 30, 2022.

The following table summarizes the Company’s option activity during the six months ended June 30, 2022:


	NUMBER OF SHARES			WEIGHTED AVERAGE EXERCISE PRICE PER SHARE		WEIGHTED AVERAGE REMAINING CONTRACTUAL TERM		AGGREGATE INTRINSIC VALUE (1)
						(In years)		(In thousands)
Outstanding as of December 31, 2021		4,763,489		$	12.56		6.44	$	10,370
Granted		1,214,325			5.85
Exercised		—			—
Forfeited/Cancelled		(514,873	)		13.02
Outstanding as of June 30, 2022		5,462,941		$	11.03		6.39	$	13
Exercisable as of June 30, 2022		3,040,043		$	9.88		4.90	$	-
Vested and expected to vest as of June 30, 2022		5,462,941		$	11.03		6.39	$	13

The aggregate intrinsic value of stock options exercised during the three months ended June 30, 2022 and 2021 was $0.0 million and $3.3 million, respectively. The aggregate intrinsic value of stock options exercised during the six months ended June 30, 2022 and 2021 was $0.0 million and $4.3 million, respectively.

The following table summarizes the Company’s restricted stock unit activity during the six months ended June 30, 2022


	NUMBER OF SHARES			WEIGHTED AVERAGE GRANT DATE FAIR VALUE

Outstanding as of December 31, 2021		—		$	—
Granted		906,683			5.62
Vested		—
Forfeited/Cancelled		(77,856	)		5.84
Outstanding as of June 30, 2022		828,827		$	5.60
Vested and expected to vest as of June 30, 2022		828,827		$	5.60

The following table presents the components and classification of stock-based compensation expense (in thousands):


	THREE MONTHS ENDED JUNE 30,				SIX MONTHS ENDED JUNE 30,
	2022		2021		2022		2021
Research and development	$	819	$	1,221	$	2,141	$	2,279
General and administrative		1,849		1,469		2,876		2,684
	$	2,668	$	2,690	$	5,017	$	4,963

Employee	$	2,481	$	2,620	$	4,456	$	4,859
Non-employee		187		70		561		104
	$	2,668	$	2,690	$	5,017	$	4,963

As of June 30, 2022, the total unrecognized compensation expense related to the Company’s stock compensation awards was $19.9 million, which the Company expects to recognize over a weighted-average period of approximately 2.6 years.