Equity Incentive Plans (Tables)

9 Months Ended

Sep. 30, 2022

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of stock option activity

	Options Outstanding
				Weighted-
				Average	Aggregate
		Weighted-		Remaining	Intrinsic
	Number	Average		Contractual	Value
	of Shares	Exercise Price		Life (years)	(in thousands)
Balances, December 31, 2021	7,162,676	$	11.25	8.2	$	21
Granted	404,700		1.93
Exercised	(16,666)		4.56
Cancelled	(727,692)		8.69
Balances, September 30, 2022	6,823,018	$	3.79	7.5	$	8
Vested and expected to vest at September 30, 2022	6,823,018	$	3.79	7.5	$	8
Exercisable at September 30, 2022	4,252,602	$	4.32	6.8	$	8
Vested at September 30, 2022	4,252,602	$	4.32	6.8	$	8

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2022		2021		2022		2021
Expected life (in years)	—		6.01		5.88		5.97
Volatility	—	%	90.0	%	85.9	%	91.4	%
Risk-free interest rate	—	%	1.0	%	3.2	%	0.6	%

Schedule of summarizes RSU activity

		Weighted-Average
	Number	Grant Date
	of Shares	Fair Value per RSU
Unvested Balances, December 31, 2021	867,730	$	6.15
RSUs Vested	(384,390)		6.15
RSUs Cancelled	(130,720)		6.15
Unvested Balances, September 30, 2022	352,620	$	6.15

Schedule of stock-based compensation expense

The compensation expense is allocated on a departmental basis, based on the classification of the option holder, as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2022		2021		2022		2021
Research and development	$	1,869	$	1,946	$	6,576	$	6,080
General and administrative		2,015		1,907		7,132		6,055
	$	3,884	$	3,853	$	13,708	$	12,135

2019 Employee Stock Purchase Plan

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2022		2021		2022		2021
Expected life (in years)	0.5 - 2.0		0.5 - 2.0		0.5 - 2.0		0.5 - 2.0
Volatility	88.0 - 96.7	%	91.1 - 98.5	%	79.0 - 96.7	%	91.1 - 107.6	%
Risk-free interest rate	3.3 - 3.5	%	0.1 - 0.2	%	0.6 - 3.5	%	0.1 - 0.2	%