Stock Incentive Plans (Tables)

9 Months Ended

Sep. 30, 2022

Share-Based Payment Arrangement [Abstract]

Schedule of Stock Options Valuation Assumptions Using a Black-Scholes Option Pricing Model

The assumptions used in the Black-Scholes option pricing model are as follows:

	Three months ended September 30,		Nine months ended September 30,
	2022	2021	2022	2021
Expected volatility	70.1%	66.3% - 71.7%	68.7% - 70.1%	64.6% - 71.7%
Weighted-average risk-free interest rate	3.2% - 3.66%	0.81% - 1.03%	1.46% - 3.66%	0.50% - 1.20%
Expected dividend yield	— %	— %	— %	— %
Expected term (in years)	6.25	6.25	5.5 - 6.25	5.5 - 6.25
Underlying common stock fair value	$1.82-$2.82	$6.36-$7.75	$1.78-$4.17	$6.36-$13.91

Summary of Option Activity under Plans

The following table summarizes the Company’s stock option activity for the nine months ended September 30, 2022:

	Number of Options			Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value
								(in thousands)
Outstanding at January 1, 2022		7,624,306		$	14.25		7.5	$	2,069
Granted		2,895,055		$	2.70
Exercised		(293	)	$	2.71
Cancelled/Forfeited		(899,370	)	$	9.92
Outstanding at September 30, 2022		9,619,698		$	11.18		7.3	$	717
Vested and expected to vest at    September 30, 2022		9,619,698		$	11.18		7.3	$	717
Exercisable at September 30, 2022		5,716,593		$	13.29		6.3	$	717

Summary of Company's RSU Activity

The following table summarizes the Company’s RSU activity for the nine months ended September 30, 2022:

	Number of Restricted Stock Units			Weighted- Average Grant Date Fair Value
Outstanding at January 1, 2022		307,600		$	12.75
Granted		400,495		$	2.70
Vested		(103,590	)	$	12.66
Forfeited		(77,546	)	$	6.32
Outstanding at September 30, 2022		526,959		$	6.08

Schedule of Stock-Based Compensation Expense

The Company recorded stock-based compensation expense related to stock options, shares purchased under the 2018 ESPP and restricted stock units as follows:

	Three months ended September 30,				Nine months ended September 30,
	2022		2021		2022		2021
	(in thousands)
Research and development	$	889	$	2,145	$	4,143	$	6,304
General and administrative		1,882		2,081		5,822		6,278
	$	2,771	$	4,226	$	9,965	$	12,582