Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2022

Stock-Based Compensation

Summary of stock option activity

	Options Outstanding and Exercisable
				Weighted
		Weighted		Average	Aggregate
		Average		Remaining	Intrinsic
	Number of	Exercise		Contractual	Value(1)
	Shares	Price		Life (Years)	(in thousands)
Outstanding as of December 31, 2021	4,545,794	$	14.15	8.1	$	2,860
Granted	1,704,850	$	5.39	—		—
Exercised	(50,420)	$	1.32	—		—
Forfeitures	(818,944)	$	13.76	—		—
Outstanding as of June 30, 2022	5,381,280	$	11.56	8.1	$	1,935
Exercisable as of June 30, 2022	2,444,111	$	12.84	7.0	$	1,870

(1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value of the common stock for the options that were in the money at June 30, 2022 and December 31, 2021.

Summary of stock based compensation expense recorded

	Three Months Ended				Six Months Ended
	June 30,				June 30,
(in thousands)	2022		2021		2022		2021
Research and development	$	728	$	1,056	$	1,496	$	2,014
General and administrative		1,514		1,731		3,374		3,281
Total stock-based compensation expense	$	2,242	$	2,787	$	4,870	$	5,295

Summary of assumptions used in the Black Scholes option pricing model for stock options granted

	Six Months Ended
	June 30,
	2022		2021
Expected term	5.5 - 6.1	years	5.5 - 6.1	years
Expected volatility	79.7	%	79.7	%
Risk free interest rate	1.8 - 3.1	%	0.8 - 1.4	%
Expected dividend yield	—	%	—	%