Equity Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2018

Equity Incentive Plans

Schedule of stock-based compensation expense

	Year Ended December 31,
	2018		2017		2016
Research and development	$	1,274	$	1,184	$	1,063
General and administrative		2,356		2,467		2,362
Total	$	3,630	$	3,651	$	3,425

Schedule of assumptions used to compute employee stock-based compensation

	2018		2017		2016
Risk-free interest rate	2.57	%	2.27	%	1.48	%
Expective volatility	70.0	%	73.9	%	75.0	%
Expected dividend yield	0	%	0	%	0	%
Expected life (in years)	6.25		6.25		6.25

Summary of options outstanding, vested and exercisable

		Weighted		WeightedAverage
		Average		Remaining	Aggregate
		Exercise		Contractual	Intrinsic
	Options	Price		Life (Years)	Value
Options outstanding at December 31, 2016	2,844,970	$	6.97	7.5
Options granted	1,145,750		2.64
Options exercised	(76,610)		1.98
Options cancelled/forfeited	(108,805)		7.62
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 exercisable at December 31, 2018	3,430,512		5.48	6.4	$	—
Vested and expected to vest at December 31, 2018	5,687,901				$	—

Schedule of restricted stock activity

		Weighted Average
		Grant Date Fair		Aggregate
	Shares	Value		Intrinsic Value
Restricted stock outstanding at December 31, 2016	33,334	$	5.93
Granted	247,694		2.97
Vested	(16,667)		5.93	$	38
Cancelled/forfeited	—		—
Restricted stock outstanding at December 31, 2017	264,361		3.16
Granted	108,254		3.46
Vested	(225,061)		3.39	$	370
Cancelled/forfeited	—		—
Restricted stock outstanding at December 31, 2018	147,554		3.03