Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2020

Share-based Payment Arrangement [Abstract]

Schedule of Stock-Based Compensation Expense

Total stock-based compensation expense recognized in the condensed consolidated statements of operations and comprehensive loss for the three months endedMarch 31, 2020 and 2019 was as follows (in thousands):

	Three Months Ended March 31,
	2020		2019
Research and development	$	1,181	$	1,097
General and administrative	1,437		1,445
Total stock-based compensation expense	$	2,618	$	2,542

Schedule of Restricted Stock Activity

The Company has also granted RSUs to its employees under the 2017 Plan. The following table summarizes RSU activity for the three months ended March 31, 2020 (in thousands, except per share amounts):

	RSUs		Weighted-Average Grant Date Fair Value per Share
Unvested as of December 31, 2019	460		$	5.61
Issued	408		$	6.55
Vested	(101	)	$	4.40
Cancelled	(7	)	$	6.83
Unvested as of March 31, 2020	760		$	6.27

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

The fair value of stock options granted during the three months endedMarch 31, 2020 and 2019 was calculated on the date of grant using the following weighted-average assumptions:

	Three Months Ended March 31,
	2020		2019
Risk-free interest rate	1.4	%	2.6	%
Expected dividend yield	—	%	—	%
Expected term (in years)	6.1		6.1
Expected volatility	71.4	%	68.9	%

Schedule of Stock Options, Activity

The following table summarizes stock option activity during the three months ended March 31, 2020 (in thousands, except per share amounts):

	Options		Weighted-Average Exercise Price		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at December 31, 2019	5,735		$	8.76	7.2	$	18,959
Granted	957		$	6.66
Exercised	(9	)	$	4.21
Cancelled	(40	)	$	9.18
Outstanding at March 31, 2020	6,643		$	8.46	7.3	$	5,855
Exercisable at March 31, 2020	3,845		$	7.69	6.2	$	5,264