The Company’s 2020 Performance Incentive Plan (the “2020 Plan”), which was adopted by the Company’s board of directors in June 2020 and approved by the Company’s stockholders in July 2020, became effective upon the consummation of the Company’s initial public offering (“IPO”). Upon the effectiveness of the 2020 Plan, no further grants may be made under the Company’s 2015 Equity Incentive Plan (the “2015 Plan”). The Company’s 2020 Plan allows for the grant of incentive stock options, non-qualified stock options, stock appreciation rights, stock bonuses, restricted stock, stock units and other forms of awards including cash awards to its officers, directors, employees, consultants and advisors.

A total of 5,945,002 shares of the Company’s common stock is authorized for issuance with respect to awards granted under the 2020 Plan. The share limit will automatically increase on the first trading day in January of each year by an amount equal to the lesser of (1) 5% of the total number of outstanding shares of the Company’s common stock on the last trading day in December in the prior year, or (2) such lesser number as determined by the Company’s board of directors. Any shares subject to awards granted under the 2020 Plan or the 2015 Plan that are not paid, delivered or exercised before they expire or are canceled or terminated, or otherwise fail to vest, as well as shares used to pay the purchase or exercise price of such awards or related tax withholding obligations, will become available for new award grants under the 2020 Plan.

The following table summarizes the option activity under the 2020 Plan and 2015 Plan during the six months ended June 30, 2022:


	Number of shares			Weighted- average exercise price		Weighted- average remaining contractual term (in years)
Outstanding at December 31, 2021		4,204,686		$	19.19		8.2
Granted		1,642,598			12.51
Exercised		(109,450	)		3.76
Forfeited		(480,080	)		20.47
Outstanding at June 30, 2022		5,257,754		$	17.31		8.0
Exercisable at June 30, 2022		2,078,037		$	16.32		6.8
Vested and expected to vest at June 30, 2022		5,257,754		$	17.31		8.0

The weighted-average grant date fair value of stock option grants was $8.49 per share for the six months ended June 30, 2022.

The following table summarizes the restricted stock unit activity under the 2020 Plan during the six months ended June 30, 2022:


	Number of shares			Weighted-average grant date fair value per share
Outstanding at December 31, 2021		—		$	—
Granted		356,908			12.18
Forfeited		(36,630	)		12.14
Vested		—			—
Outstanding at June 30, 2022		320,278		$	12.18

The Company’s 2020 Employee Stock Purchase Plan (the “ESPP”), which was adopted by the Company’s board of directors in June 2020 and approved by the Company’s stockholders in July 2020, became effective upon the consummation of the IPO. A total of 952,524 shares of the Company’s common stock is available for issuance under the ESPP. The ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to any plan limitations. The ESPP provides for six-month offering periods, and at the end of each offering period, employees are able to purchase shares at 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 last trading day of the offering period. As of June 30, 2022, no shares had been issued under the ESPP, and the full number of shares authorized under the ESPP was available for issuance purposes.

Shares subject to repurchase by the Company were 2,475 shares and 16,181 shares, and the related liability recorded under other long-term liabilities in the condensed balance sheets was insignificant as of June 30, 2022 and December 31, 2021, respectively.

Share-based compensation expense for the three and six months ended June 30, 2022 and 2021 was as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Research and development	$	1,602	$	1,744	$	3,457	$	3,314
General and administrative		2,310		1,946		4,552		3,723
Total share-based compensation	$	3,912	$	3,690	$	8,009	$	7,037

The total unrecognized compensation cost related to unvested stock options was $44.5 million, which is expected to be recognized over a weighted-average remaining service period of 2.60 years as of June 30, 2022. The total unrecognized compensation cost related to unvested restricted stock units was $3.9 million, which is expected to be recognized over a weighted-average remaining service period of 3.69 years as of June 30, 2022.