Stock incentive plan (Tables)

3 Months Ended

Mar. 31, 2020

Stock incentive plan

Allocation of stock-based compensation expenses

Non-cash stock-based compensation expense recognized in the accompanying condensed statements of operations relating to both stock options, restricted stock awards, and restricted stock units for the three months ended March 31, 2020 and 2019 was as follows (in thousands):

	Three months ended
	March 31,
	2020		2019
Research and development	$	456	$	421
General and administrative		1,875		1,579
Total stock‑based compensation expense	$	2,331	$	2,000

Schedule of restricted stock unit activity

The table below summarizes activity related to restricted stock units (in thousands, except per share amounts):

		Weighted‑
		average
		grant date
		fair value
	Shares	per share
Unvested as of December 31, 2019	1,032	$	3.63
Issued	—	$	—
Vested	(6)		3.63
Forfeited and canceled	(59)		3.63
Unvested as of March 31, 2020	967	$	3.63

Summary of stock option activity

The table below summarizes activity related to stock options (in thousands, except per share amounts):

				Weighted‑
		Weighted‑		average
		average		remaining	Aggregate
		exercise		contractual	intrinsic
Options	Shares	price		term	value
Outstanding, December 31, 2019	4,798	$	8.75	8.29	$	1,159
Granted	1,939		3.09
Exercised	(104)		2.34
Forfeited and canceled	(214)		6.12
Outstanding, March 31, 2020	6,419	$	7.23	8.48	$	102
Vested and expected to vest at March 31, 2020	6,419	$	7.23	8.48	$	102
Exercisable at March 31, 2020	2,439	$	6.96	7.45	$	100