Stock Incentive Plans (Tables)

6 Months Ended

Jun. 30, 2023

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 June 30,		Six months ended June 30,
	2023	2022	2023	2022
Expected volatility	69.2% - 69.6%	69.3% - 69.6%	69.2% - 69.7%	68.7% - 69.6%
Weighted-average risk-free interest rate	3.45% - 4.03%	2.67% - 3.38%	3.45% - 4.22%	1.46% - 3.38%
Expected dividend yield	— %	— %	— %	— %
Expected term (in years)	5.5 - 6.25	5.5 - 6.25	5.5 - 6.25	5.5 - 6.25
Underlying common stock fair value	$0.92-$1.03	$1.78-$2.88	$0.92-$1.60	$1.78-$4.17

Summary of Option Activity under Plans

The following table summarizes the Company’s stock option activity for the six months ended June 30, 2023:

	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, 2023		9,865,734		$	10.96		7.2	$	493
Granted		3,188,150		$	1.53
Exercised		(3,366	)	$	0.47
Cancelled/Forfeited		(296,260	)	$	8.91
Outstanding at June 30, 2023		12,754,258		$	8.65		7.3	$	252
Vested and expected to vest at    June 30, 2023		12,754,258		$	8.65		7.3	$	252
Exercisable at June 30, 2023		7,246,788		$	12.20		6.1	$	252

Summary of Company's RSU Activity

The following table summarizes the Company's RSU activity for the six months ended June 30, 2023:

	Number of Restricted Stock Units			Weighted- Average Grant Date Fair Value
Outstanding at January 1, 2023		543,179		$	6.12
Granted		483,850		$	1.60
Vested		(194,525	)	$	6.14
Forfeited		(26,009	)	$	5.28
Outstanding at June 30, 2023		806,495		$	2.85

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 June 30,				Six months ended June 30,
	2023		2022		2023		2022
	(in thousands)
Research and development	$	628	$	1,088	$	1,277	$	3,254
General and administrative		1,774		2,055		3,494		3,940
	$	2,402	$	3,143	$	4,771	$	7,194