Equity Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2019

Equity Incentive Plans

Schedule of stock-based compensation expense

	Year Ended December 31,
	2019		2018		2017
Research and development	$	522	$	1,274	$	1,184
General and administrative		1,240		2,356		2,467
Total	$	1,762	$	3,630	$	3,651

Schedule of assumptions used to compute employee stock-based compensation

	2019					2018		2017
Risk-free interest rate	1.74	%	-	2.61	%	2.57	%	2.27	%
Expective volatility				65.0	%	70.0	%	73.9	%
Expected dividend yield				0	%	0	%	0	%
Expected life (in years)				6.25		6.25		6.25

Summary of options outstanding, vested and exercisable

				Weighted
		Weighted		Average
		Average		Remaining
		Exercise		Contractual	Aggregate
	Options	Price		Life (Years)	Intrinsic Value
Options outstanding at December 31, 2017	3,805,305		5.74	7.4
Options granted	2,230,000		1.96
Options exercised	—		—
Options cancelled/forfeited	(347,404)		4.19
Options outstanding at December 31, 2018	5,687,901		4.34	7.4
Options granted	2,805,600		1.18
Options exercised	(92,271)		1.78
Options cancelled/forfeited	(1,208,873)		2.70
Options outstanding at December 31, 2019	7,192,357		3.42	7.2	$	5,256
Options exercisable at December 31, 2019	4,396,577		4.60	6.1	$	2,228
Vested and expected to vest at December 31, 2019	7,192,357				$	5,256

Schedule of restricted stock activity

		Weighted Average		Aggregate
	Shares	Grant Date Fair Value		Intrinsic Value
Restricted stock units outstanding at December 31, 2017	264,361		3.16
Granted	108,254		3.46
Vested	(225,061)		3.39	$	370
Restricted stock units outstanding at December 31, 2018	147,554		3.03
Vested	(147,554)		3.03	$	129
Restricted stock units outstanding at December 31, 2019	—