Equity Incentive Plans (Tables)

3 Months Ended

Mar. 31, 2018

Equity Incentive Plans

Summary of stock option activity under the Equity Plans

			Weighted
			Average		Weighted	Aggregate
			Exercise Price		Average Remaining	Intrinsic
	Options		Per Share		Life in Years	Value
Outstanding at December 31, 2017	2,257,621		$	12.38	8.66	$	68
Granted	—		$	—
Exercised	—		$	—
Forfeited	(7,541	)	$	7.24
Outstanding at March 31, 2018	2,250,080		$	12.40	8.41	$	895
Options exercisable at March 31, 2018	1,165,704		$	15.79	7.78	$	242
Options vested and expected to vest at March 31, 2018	2,250,080		$	12.40	8.41	$	895

Schedule of assumptions used to determine grant-date fair value of stock options

	Year Ended December 31,
	2017
Expected volatility	68.7	%
Weighted average risk-free interest rate	2.10	%
Expected dividend yield	0.00	%
Expected term (in years)	6.6

Schedule of stock-based compensation expense related to issuance of stock option awards recognized in condensed consolidated statements of operations and comprehensive loss

	Three Months Ended March 31,
	2018		2017
	(in thousands)
Research and development	$	117	$	1,678
General and administrative	611		1,945
Total	$	728	$	3,623