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 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. As of March 31, 2021, there were an aggregate of 2,061,754 shares of common stock issuable upon the exercise of outstanding options under the 2015 Plan. Any options or awards outstanding under the 2015 Plan remain outstanding and effective.

A total of 4,295,638 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 (commencing in 2021) 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. A total of 715,770 options had been granted under the 2020 Plan for the three months ended March 31, 2021, and 2,325,631 shares was available for issuance under the 2020 Plan as of March 31, 2021.

The following table summarizes the option activity under the 2020 Plan and 2015 Plan during the three months ended March 31, 2021:

	Number of shares			Weighted- average exercise price		Weighted- average remaining contractual term (in years)
Outstanding at December 31, 2020		3,640,715		$	11.00		9.0
Granted		715,770			53.39
Exercised		(155,322	)		4.87
Forfeited		(15,732	)		18.23
Outstanding at March 31, 2021		4,185,431		$	18.45		9.0
Exercisable at March 31, 2021		745,999		$	8.10		8.5
Vested and expected to vest at March 31, 2021		4,185,431		$	18.45		9.0

The weighted-average grant date fair value of stock option grants was $36.29 per share for the three months ended March 31, 2021.

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 622,652 shares of the Company’s common stock is initially 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 March 31, 2021, no shares had been issued under the ESPP, and the full number of shares authorized under the ESPP Plan was available for issuance purposes.

Shares subject to repurchase by the Company were 62,424 shares and 77,393 shares, with the related liability of $0.1 million and $0.1 million recorded under other long-term liabilities in the balance sheets as of March 31, 2021 and December 31, 2020, respectively.

Share-based compensation expense for the three months ended March 31, 2021 and 2020 were as follows (in thousands):

	Three Months Ended March 31,
	2021		2020
Research and development	$	1,570	$	192
General and administrative		1,777		290
Total share-based compensation	$	3,347	$	482

The total unrecognized compensation cost related to unvested share-based awards was $44.6 million, which is expected to be recognized over a weighted-average remaining service period of 3.5 years as of March 31, 2021.

The fair value of stock options was estimated on the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:

	Three Months Ended March 31,
	2021			2020
Common stock fair value	$	53.39		$	4.29
Risk-free interest rate		0.69	%		0.51	%
Expected volatility		79.86	%		87.78	%
Expected term (in years)		6.0			6.0
Expected dividend yield		—	%		—	%

As of March 31, 2021, the Company had reserved the following shares of common stock for future issuance:

	March 31, 2021
Common stock options granted and outstanding		4,185,431
Reserved for future equity award grants		2,325,631
Reserved for future ESPP issuances		622,652
		7,133,714