Stock Based Compensation (Tables)

6 Months Ended

Jun. 30, 2021

Share-based Payment Arrangement [Abstract]

Summary of stock option activity

The following table summarizes option activity under the Plan:

	Shares Available For Grant			Options and restricted stock awards			Weighted Average Exercise Price		Weighted Average Contractual Term (in Years)
Balance as of January 1, 2021		28,974,067			18,724,096			0.69		6.5
Granted		(849,978	)		849,978			16.60
Exercised		—			(901,406	)		0.23
Restricted stock unit awards released		—			(97,059	)		N/A
Forfeited or surrendered for taxes		385,867			(360,313	)		3.39
Balance as of June 30, 2021		28,509,956			18,215,296			1.26		6.1

Summary of Share-based Payment Award, Stock Options, Valuation Assumptions

The fair value of each stock option grant under the Plan was estimated on the date of grant using the Black-Scholes option pricing model, with the following range of assumptions:

	Six-months Ended June 30, 2021
Expected term (in years)		6.3
Volatility		90.2% to 99%
Dividend yield		0.0%
Risk-free interest rate		0.63% to 1.22%
Common stock price		$19.28

Summary of Stock-based compensation expense

Stock-based compensation expense is as follows (in thousands):

	Three-months Ended June 30,
	2021		2020
General and administrative expense	$	444	$	30
Research and development		1,774		22
Total		2,218		52

	Six-months Ended June 30,
	2021		2020
General and administrative expense	$	617	$	38
Research and development		2,418		32
Total		3,035		70