Equity Plans (Tables)

3 Months Ended

Mar. 31, 2018

Schedule of activity under equity incentive plans

		Weighted-		Weighted-
		Average		Average
		Exercise		Remaining	Aggregate
	Number of	Price Per		Contractual	Intrinsic
	Options	Share		Life (years)	Value
					(in millions)
Outstanding at December 31, 2017	2,438,151	$	11.51	8.26
Granted	629,950		16.91
Exercised	(50,507)		4.40
Forfeited	(33,072)		20.12
Outstanding at March 31, 2018	2,984,522	$	12.67	8.52	$	5.9
Exercisable – March 31, 2018	952,059	$	9.92	7.81	$	3.3
Vested and expected to vest – March 31, 2018	2,984,522	$	12.67	8.52	$	5.9

⁽¹⁾ The aggregate intrinsic values were calculated as the difference between the exercise price of the options and the closing price of the Company’s common stock on March 31, 2018. The calculation excludes options with an exercise price higher than the closing price of the Company’s common stock on March 31, 2018.

Schedule of stock-based compensation expense

Total stock-based compensation expense was as follows (in thousands):

	Three Months Ended
	March 31,
	2018		2017
Research and development	$	541	$	359
General and administrative		644		484
Total stock-based compensation expense	$	1,185	$	843

Director And Employee [Member]

Schedule of valuation assumptions

	Three Months Ended
	March 31,
	2018	2017
Expected term (in years)	6.02 - 6.08	6.08
Expected volatility	66.38% - 66.47%	62.5%
Risk-free interest rate	2.42% - 2.73%	2.07%
Dividend yield	—	—

2016 Employee Stock Purchase Plan [Member]

Schedule of activity under equity incentive plans

Un
			Weighted-
			Average
	Number of		Grant Date
	Shares		Fair Value
Unvested at December 31, 2017	—		—
Granted	113,625	$	16.95
Unvested at March 31, 2018	113,625	$	16.95