Equity Incentive Plan (Tables)

3 Months Ended

Mar. 31, 2020

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, 2019	3,742,144	$	9.58	8.6	$	22,910
Granted*	636,000		22.02
Exercised	(86,872)		4.82
Cancelled	(6,690)		11.43
Balances, March 31, 2020	4,284,582	$	11.52	8.6	$	25,368
Vested and expected to vest at March 31, 2020	4,284,582	$	11.52	8.6	$	25,368
Exerciseable at March 31, 2020	1,888,288	$	6.65	7.8	$	18,813
Vested at March 31, 2020	1,374,666	$	7.21	7.7	$	12,954

  *  The board of directors of the Company approved the grant of 564,800 stock options on February 26, 2020. As the Company prioritized other communications including COVID-19 related matters, the terms of the 564,800 stock options were not communicated until April 2020. As a result, the Company excluded these options from the computation of expense and option activity in the quarter ended March 31, 2020. These options will be included in the second Quarterly Report on Form 10-Q.

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

	Three Months Ended March 31,
	2020		2019
Expected life (in years)	5.95		6.02
Volatility	84.9	%	80.8	%
Risk-free interest rate	1.19	%	2.46	%

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 March 31,
	2020		2019
Research and development	$	1,058	$	419
General and administrative		1,424		357
	$	2,482	$	776

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 March 31,
	2020
Expected life (in years)	0.5 - 2.0
Volatility	91.4 - 106.8	%
Risk-free interest rate	0.86 -  1.11	%