In October 2020, the Company’s shareholders approved the Company’s 2020 Incentive Award Plan (“2020 Plan”). The 2020 Plan initially provided for the issuance of up to 7,924,000 shares of common stock and for the grant of incentive stock options or other incentive awards to employees, officers, directors and consultants of the Company. The number of shares of common stock that may be issued under the 2020 Plan is also subject to increase on the first day of each calendar year equal to the lesser of i) 5% of the aggregate number of shares of common stock outstanding on the final day of the immediately preceding calendar year or ii) such smaller number of shares as is determined by the board of directors. Through December 31, 2022, the shares available under the plan were increased by 8,285,983 shares. As of December 31, 2022 there were 7,961,066 shares of common stock remaining available for future issuance under the 2020 Plan. In January 2023, the shares of the Company's common stock available under the 2020 Plan were increased by 4,164,381 shares.

The 2020 Plan replaced and is the successor of the Company’s 2013 Equity Incentive Plan, as amended (“2013 Plan”). Upon any cancellation of outstanding option awards to purchase up to 5,982,266 shares of common stock under the 2013 Plan, such shares will be made available for grant under the 2020 Plan.

During the year ended December 31, 2022, the Company granted 182,350 restricted stock units to employees with an aggregate grant date fair market value of $1,302. The restricted stock unit awards vest in three annual installments, the first of which occurred on January 31, 2023. No restricted stock units were granted during the years ended December 31, 2021 and 2020. During the year ended December 31, 2022, 20,600 restricted stock units were cancelled due to terminations.


	Number of Shares			Weighted Average Grant Date Fair Value
Outstanding at January 1, 2022		—		$	—
Granted		182,350		$	7.14
Release		—		$	—
Cancelled		(20,600	)	$	7.14
Unvested shares at December 31, 2022		161,750		$	7.14

During the year ended December 31, 2022, the Company granted 742,070 performance-based restricted stock units to employees with an aggregate grant date fair value of $5,298. No performance-based restricted stock units were granted during the years ended December 31, 2021 and 2020. The performance stock unit awards provide for a performance period from February 1, 2022 through January 31, 2025 to achieve up to six defined performance metrics. The percentage of each award eligible to vest will be determined based on the number of metrics achieved during the performance period and may range from 0% to 200%. The Company has not recognized any compensation expense through December 31, 2022, as the minimum performance criteria had not been deemed probable. The vesting of any eligible awards will occur in equal installments on January 31, 2025 and January 31, 2026.

During the year ended December 31, 2022, 17,100 performance-based restricted stock units were cancelled due to terminations.


	Number of Shares			Weighted Average Grant Date Fair Value
Outstanding at January 1, 2022		—		$	—
Granted		742,070		$	7.14
Release		—		$	—
Cancelled		(17,100	)	$	7.14
Unvested shares at December 31, 2022		724,970		$	7.14

In October 2020, the Company’s shareholders approved the ESPP, which became effective upon the closing of the Company’s IPO in November 2020. The Company initially reserved a total of 1,187,000 shares of its common stock for issuance under the ESPP. The ESPP provides that the number of shares reserved and available for issuance under the ESPP will be increased on January 1 of each calendar year by 1% of the number of shares of the Company's common stock issued and outstanding on the immediately preceding December 31 or such lesser amount as specified by the board of directors. Through December 31, 2022, there was no increase in the number of shares reserved for issuance under the ESPP. In January 2023, the number of shares of the Company's common stock available for issuance under the ESPP was increased by 832,876 shares.

In April 2022, the Company initiated its first offering period under the ESPP. Each offering period is six months in duration with the purchase date being the last trading day of the offering period. On September 30, 2022, the first offering period concluded and the Company issued 29,036 shares of its common stock for proceeds of $140.

The following summarizes stock option activity:


	Number of Shares			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value ($000s)
Outstanding at January 1, 2022		10,516,972		$	22.87		8.1	$	31,239
Granted		3,884,917		$	7.08
Exercised		(155,873	)	$	1.48
Cancelled		(613,738	)	$	25.87
Outstanding at December 31, 2022		13,632,278		$	18.48		7.7	$	10,937
Vested and expected to vest at December 31, 2022		13,632,278		$	18.48		7.7	$	10,937
Vested and exercisable at December 31, 2022		7,459,247		$	16.11		7.0	$	10,348

The aggregate intrinsic value of options granted is calculated as the difference between the exercise price of the options and the estimated fair value of the Company’s common stock for those options that had exercise prices lower than the fair value of the Company’s common stock.

Option grants generally vest over a service period of three or four years and have a contractual term of ten years. As of December 31, 2022, total unrecognized compensation expense related to stock option awards was $92,798, which amount is being recognized over a remaining weighted average period of 2.3 years.

The weighted average grant date fair value per option granted during the years ended December 31, 2022, 2021 and 2020 was $5.09, $39.10 and $14.93, respectively. The fair value of each award was estimated using Black-Scholes based on the following assumptions:


	For the Year Ended December 31,
	2022			2021			2020
Risk-free interest rate		2.10	%		0.80	%	0.31 - 0.56%
Expected term	5.96 years			5.99 years			6.25 years
Expected volatility		85.0	%		85.0	%	80.0% - 91.7%
Expected dividend yield		0	%		0	%		0	%

Stock-based compensation expense is classified as follows:


	For the Year Ended December 31,
	2022		2021		2020
Research and development expense	$	21,870	$	18,127	$	3,565
General and administrative		24,848		21,494		3,892
Total stock-based compensation expense	$	46,718	$	39,621	$	7,457

The components of stock-based compensation expense were:


	For the Year Ended December 31,
	2022		2021		2020
Restricted common stock	$	—	$	—	$	657
Restricted stock units		352		—		—
Performance-based restricted stock units		—		—		—
Stock options		46,220		39,621		6,800
ESPP		145		—		—
Total stock-based compensation expense	$	46,718	$	39,621	$	7,457