Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Restricted Common Stock Activity

The following table summarizes restricted common stock activity for the nine months ended September 30, 2020:

	Shares			Weighted Average Grant Date Fair Value
Unvested as of January 1, 2020		4,403,148		$	1.87
Granted		171,204			13.17
Forfeited		(6,710	)		3.01
Vested		(1,013,154	)		1.88
Unvested as of September 30, 2020		3,554,488		$	2.41

Summary of Stock Option Activity

The following table summarizes stock option activity (in thousands, except share and per share data):

	Stock Options
	Shares		Weighted Average Exercise Price		Weighted Average Contractual Life (in years)		Aggregate Intrinsic Value
Options outstanding as of January 1, 2020		44,960	$	3.01		9.5		—
Granted		3,616,945		16.89
Exercised		—		—
Forfeited		—		—
Options outstanding as of September 30, 2020		3,661,905	$	16.72		9.8	$	39,553
Options vested and exercisable at September 30, 2020		14,048	$	3.01		9.0	$	344

Schedule of Estimated Fair Value Assumptions Using Black Scholes Option-Pricing Model

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

	Three Months Ended September 30, 2020			Nine Months Ended September 30, 2020
Expected term (in years)		6.08			6.08
Expected volatility		95.2	%		95.1	%
Risk-free interest rate		0.35	%		0.35	%
Expected dividend yield		—			—
Fair value of common stock	$	13.01		$	12.86

Schedule of Stock-based Compensation Expense

Stock-based compensation expense was as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2020		2019		2020		2019
Research and development	$	3,092	$	174	$	3,400	$	356
General and administrative		768		422		1,598		1,912
Total stock-based compensation expense	$	3,860	$	596	$	4,998	$	2,268