Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Stock-Based Compensation

Summary of stock option activity

	Options Outstanding and Exercisable
				Weighted
		Weighted		Average	Aggregate
		Average		Remaining	Intrinsic
	Number of	Exercise		Contractual	Value(1)
	Shares	Price		Life (Years)	(in thousands)
Outstanding as of January 1, 2018	506,586	$	0.94	9.0	$	137
Granted	1,570,136	$	5.92	9.9		—
Exercised	(5,599)	$	0.84	—		—
Forfeitures	(14,232)	$	1.11	—		—
Outstanding as of December 31, 2018	2,056,891	$	4.74	9.4	$	5,946
Granted	258,897	$	18.88	9.5		—
Exercised	(125,108)	$	0.96	7.4		—
Forfeitures	(20,468)	$	19.66	9.5		—
Outstanding as of December 31, 2019	2,170,212	$	6.51	8.6	$	—
Vested and expected to vest as of December 31, 2019	2,170,212	$	6.51	—	$	113,295
Exercisable as of December 31, 2019	716,393	$	3.75	—	$	39,370

(1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value of the common stock for the options that were in the money at December 31, 2019 and 2018.

Summary of stock based compensation expense recorded

	Year Ended
	December 31,
	2019		2018
Research and development	$	691	$	85
General and administrative		1,195		178
Total stock-based compensation expense	$	1,886	$	263

Summary of assumptions used in the Black Scholes option pricing model for stock options granted

	Year Ended
	December 31,
	2019		2018
Expected term	6.1	years	6.1	years
Expected volatility	69.7	%	69.7	%
Risk free interest rate	1.90	%	2.77	%
Expected dividend yield	—	%	—	%