In February 2020, the Company’s Board of Directors adopted, and its stockholders approved, the 2020 Equity Incentive Plan (the 2020 Plan), which became effective in April 2020 in connection with the Company’s IPO. The 2020 Plan provides for the grants of stock options and other equity-based awards to employees, non-employee directors, and consultants of the Company. Upon adoption of the 2020 Plan, the Company restricted the grant of future equity awards under its 2014 Equity Incentive Plan, as amended and restated (the 2014 Plan).

Stock options granted under the 2020 Plan and the 2014 Plan become exercisable at various dates as determined by the Company’s Board of Directors or its authorized committee and will expire no more than ten years from their date of grant. Stock options generally vest over a four-year term. The exercise price of each option is determined by the Company’s Board of Directors, although generally options have an exercise price equal to the fair market value of the Company’s stock on the date of the option grant. In the case of incentive stock options, the exercise price shall not be less than 100% of the fair market value of the Company’s common stock at the time the option is granted. For holders of more than 10% of the Company’s total combined voting power of all classes of stock, incentive stock options may not be granted at less than 110% of the fair market value of the Company’s common stock at the date of grant and for a term not to exceed five years.

As of December 31, 2021, there were 1,831,539 shares available for future issuance under the 2020 Plan. The 2020 Plan share reserve will be increased by the number of shares under the 2014 Plan that are repurchased, forfeited, expired or cancelled after

the effective date of the 2020 Plan up to the limit under the 2020 Plan. In addition, the number of shares of the Company’s common stock available for issuance under the 2020 Plan will automatically increase on the first day of each fiscal year, beginning with the Company’s 2021 fiscal year, in an amount equal to the lessor of (1) 2,656,500 shares, (2) 5% of the outstanding shares of the Company’s common stock on the last day of the immediately preceding fiscal year, or (3) such other amount as determined by the Company’s Board of Directors.

The following table summarizes the option activity for the year ended December 31, 2021:


	Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2020		3,996,174		$	9.03
Granted		1,694,692			26.55
Exercised		(160,303	)		6.26
Forfeited and cancelled		(262,243	)		21.02
Outstanding at December 31, 2021		5,268,320		$	14.16		7.9	$	25,633
Exercisable at December 31, 2021		2,317,374		$	6.76		7.1	$	19,965

The total intrinsic value of options exercised was $2.2 million, $2.7 million and $0.1 million for the years ended December 31, 2021, 2020 and 2019, respectively.

In February 2020, the Company’s Board of Directors adopted, and its stockholders approved, the 2020 Employee Stock Purchase Plan (ESPP). The first offering period began in December 2021 and the first purchase under the ESPP will be in 2022. A total of 290,000 shares of common stock were reserved for future issuance under the ESPP. Further, the number of shares of common stock available for issuance under the ESPP will automatically increase on the first day of each fiscal year following the fiscal year in which the first offering period under the ESPP commences in an amount equal to the lessor of (1) 500,000 shares, (2) 1% of the outstanding shares of the Company’s common stock on the last day of the immediately preceding fiscal year, or (3) such other amount as determined by the Company’s Board of Directors. As of December 31, 2021, no shares had been issued pursuant to the ESPP and the associated compensation expense was immaterial for the year ended December 31, 2021.

Stock option awards and ESPP grants are valued using the Black-Scholes Merton option pricing model on the date of grant. This option pricing model involves a number of estimates, including the expected lives of the stock options, the Company’s anticipated stock volatility and interest rates. Stock-based compensation expense is recognized over the vesting period. Forfeitures are recognized as they occur.

The fair value of stock option awards to employees, executives, directors, and other service providers was estimated at the date of grant using the Black-Scholes Merton option pricing model with the following assumptions.


	Years Ended December 31,
	2021	2020	2019
Stock price	$13.36 - $35.67	$16.00 - $35.92	$1.60 - $9.16
Risk-free interest rate	0.60% - 1.34%	3.17% - 5.59%	1.4% - 2.6%
Expected volatility	82.34% - 88.43%	88.01% - 95.11%	77% - 104%
Expected term (in years)	5.50 - 6.08	5.50 - 6.08		6.10
Expected dividend yield	0%	0%	0%

The weighted-average grant-date fair value of options granted was $19.21, $12.99 and $5.01 for the years ended December 31, 2021, 2020 and 2019, respectively.

The total unrecognized compensation expense related to outstanding unvested stock-based awards as of December 31, 2021, was $36.4 million, which is expected to be recognized over a weighted-average remaining service period of 2.54 years.

The table below summarizes the total stock-based compensation expense included in the Company’s statements of operations and comprehensive loss for stock options for the periods presented (in thousands):


	Years Ended December 31,
	2021		2020		2019
Research and development	$	4,959	$	2,025	$	476
General and administrative		7,894		3,253		618
Total stock-based compensation expense	$	12,853	$	5,278	$	1,094