Equity Incentive Plans (Tables)

6 Months Ended

Jun. 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	(422,345)		10.95
Balances, June 30, 2022	7,128,365	$	3.87	7.8	$	19
Vested and expected to vest at June 30, 2022	7,128,365	$	3.87	7.8	$	19
Exercisable at June 30, 2022	3,984,931	$	4.58	7.0	$	10
Vested at June 30, 2022	3,984,931	$	4.58	7.0	$	10

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Expected life (in years)	5.87		5.87		5.88		5.97
Volatility	86.0	%	89.5	%	85.9	%	91.4	%
Risk-free interest rate	3.2	%	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 Cancelled	(78,340)		6.15
Unvested Balances, June 30, 2022	789,390	$	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 June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Research and development	$	2,639	$	1,918	$	4,707	$	4,134
General and administrative		2,848		1,964		5,117		4,148
	$	5,487	$	3,882	$	9,824	$	8,282

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 June 30,				Six Months Ended June 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	79.0 - 89.9	%	93.9 - 107.6	%	79.0 - 89.9	%	93.9 - 107.6	%
Risk-free interest rate	0.6 - 1.3	%	0.1	%	0.6 - 1.3	%	0.1	%