In November 2018, the Company adopted, and its stockholders approved, the 2018 Stock Option and Grant Plan (the “2018 Plan”), which provides for the granting of stock options and other equity-based awards at the discretion of the Board of Directors or any subcommittee of the Board of Directors to its employees, officers, directors, and independent contractors. No further grants will be made under the 2018 Plan. However, the 2018 Plan will continue to govern outstanding equity awards granted thereunder. To the extent outstanding options granted under the 2018 Plan are cancelled, forfeited or otherwise terminated without being exercised and would otherwise have been returned to the share reserve under the 2018 Plan, the number of shares underlying such awards will be available for future grant under the 2020 Stock Option and Incentive Plan.

In August 2020, the Company and its stockholders approved the 2020 Stock Option and Incentive Plan (the “2020 Plan”), which became effective on August 20, 2020. The 2020 Plan replaced the 2018 Plan as the Company’s board of directors has determined not to make additional awards under the 2018 Plan following the closing of the Company’s IPO. The 2020 Plan allows the Company to make equity-based and cash-based incentive awards to its officers, employees, directors and consultants. The Company has initially reserved 4,457,370 shares of its common stock for the issuance of awards under the 2020 Plan,

which includes the shares of common stock remaining available for issuance under its 2018 Plan as of the business day immediately prior to the effective date of the registration statement. The 2020 Plan provides that the number of shares reserved and available for issuance will automatically increase on January 1, 2021 and each January 1 thereafter, by 4% of the Company’s outstanding number of shares of common stock on the immediately preceding December 31, or such lesser number of shares as determined by the Company’s compensation committee. These limits are subject to adjustment in the event of a stock split, stock dividend or other change in the Company’s capitalization. As of December 31, 2021, there were an aggregate of 3,082,121 shares remaining available for future grants.

In August 2020, the Company and its stockholders approved the 2020 Employee Stock Purchase Plan (the “2020 ESPP”), which became effective August 20, 2020. The 2020 ESPP initially reserves and authorizes the issuance of up to a total of 445,653 shares of common stock to participating employees. The 2020 ESPP provides that the number of shares reserved and available for issuance will automatically increase on January 1, 2021 and each January 1 thereafter through January 1, 2030, by the least of (i) 438,898 shares of common stock, (ii) 1% of the Company’s outstanding number of shares of common stock on the immediately preceding December 31 or (iii) such lesser number of shares of common stock as determined by the administrator of the 2020 ESPP. The number of shares reserved under the 2020 ESPP is subject to adjustment in the event of a stock split, stock dividend or other change in the Company’s capitalization. As of December 31, 2021, there were an aggregate of 864,864 shares remaining available for future grants.

A summary of stock option activity under the 2020 Stock Option and Grant Plan during the year ended December 31, 2021 is as follows (in thousands except share and per share data):


	Number of Options Outstanding			Weighted Average Strike Price per Option		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Outstanding at December 31, 2020		5,832,712		$	8.17		9.08	$	314,001
Granted		2,390,939			51.17
Exercised		(1,431,271	)		5.33
Forfeited		(553,198	)		23.76
Outstanding at December 31, 2021		6,239,182		$	23.91		8.56	$	246,933
Exercisable at December 31, 2021		1,928,457		$	12.99		8.18	$	97,387

The intrinsic value of stock options exercised during the years ended December 31, 2021, 2020 and 2019 was $67.6 million, $1.6 million and $0.1 million, respectively.

The weighted-average fair value of options granted during the years ended December 31, 2021, 2020 and 2019 was $29.95, $8.35 and $1.69 per share, respectively.

As of December 31, 2021, the total unrecognized stock-based compensation expense for unvested stock options was $66.1 million, which is expected to be recognized over 2.7 years.

The following table outlines equity-based compensation expense for stock options for the years ended December 31, 2021, 2020 and 2019:


	Year ending December 31,
	2021		2020		2019
Research and development	$	11,161	$	2,084	$	380
General and administrative		12,628		2,864		212
Total equity-based compensation	$	23,789	$	4,948	$	592

The weighted-average assumptions that the Company used in Black-Scholes option pricing model to determine the grant date fair value of stock options granted to employees and non-employees for the years ended December 31, 2021, 2020 and 2019:


	Year ending December 31,
	2021			2020			2019
Expected term (in years)		5.87		6.09				6.49
Volatility		66	%		70	%		71	%
Risk-free interest rate		0.9	%		0.5	%		1.83	%
Dividend yield		0.00	%		0.00	%		0.00	%

The Company has granted shares of restricted common stock with service-based and performance-based vesting conditions. A summary of restricted stock activity under the 2018 Plan during the year ended December 31, 2021 is as follows:


	Number of Units Outstanding			Grant Date Fair Value per Share
Unvested at December 31, 2020		110,104		$	1.60
Granted		12,500			53.50
Vested		(84,859	)		9.25
Forfeited		—			—
Unvested at December 31, 2021		37,745		$	1.60

During the year ended December 31, 2021, the Company granted 12,500 shares of restricted common stock to consultants which were fully vested at the time of grant. There were no grants of restricted stock during the years ended December 31, 2020 and 2019.

As of December 31, 2021, the total unrecognized stock-based compensation expense for unvested restricted stock was $0.1 million, which is expected to be recognized over 1.0 years.

During the years ended December 31, 2021, 2020 and 2019, the Company recorded stock-based compensation expense for restricted stock of $0.9 million, $0.2 million and $0.4 million, respectively. During the years ended December 31, 2021, 2020 and 2019, the Company recorded stock-based compensation expense of $0.3 million, $0.2 million and $0.2 million, respectively, within research and development. During the years ended December 31, 2021, 2020 and 2019, the Company recorded stock-based compensation expense of $0.6 million, an immaterial amount and $0.2 million, respectively, within general and administrative.

Total equity-based compensation expense recorded as research and development and general and administrative expenses for employees, directors, and non-employees during the years ended December 31, 2021, 2020 and 2019 is as follows (in thousands):


	Years ending December 31,
	2021		2020		2019
Research and development	$	11,731	$	2,305	$	688
General and administrative		13,241		2,885		508
Total equity-based compensation	$	24,972	$	5,190	$	1,196