Stock-Based Awards (Tables)

9 Months Ended

Sep. 30, 2016

Stock-Based Awards

Assumptions used to determine fair value of stock options granted

	Nine Months Ended September 30,
	2016		2015
Risk-free interest rate	1.41	%	1.73	%
Expected term (in years)	6.5		6.2
Expected volatility	96.60	%	96.65	%
Expected dividend yield	0	%	0	%

Summary of stock option activity

					Weighted
			Weighted		Average
			Average		Remaining	Aggregate
	Number		Exercise		Contractual	Intrinsic
	of Shares		Price		Term	Value
					(in years)
Outstanding as of December 31, 2015	1,738,524		$	13.23	9.51	$	24,722
Granted	222,528			20.10
Exercised	(25,990)			0.55
Forfeited and canceled	(67,561)			15.69
Outstanding as of September 30, 2016	1,867,501		$	14.13	8.80	$	22,921
Options vested and expected to vest as of September 30, 2016	1,867,501		$	14.13	8.80	$	22,921
Options exercisable as of September 30, 2016	384,223	(1)	$	5.54	8.07	$	7,713

(1) All options granted under the 2012 Plan are exercisable immediately, subject to a repurchase right in the Company’s favor that lapses as the option vests. This amount reflects the number of shares under options that were vested, as opposed to exercisable, as of September 30, 2016.

Summary of RSU activity

		Weighted
		Average
		Grant Date
	Number	Fair Value
	of Shares	Per Share
Outstanding as of December 31, 2015	53,800	$	28.68
Granted	37,200		20.32
Vested	—		—
Forfeited and cancelled	(2,000)		28.68
Outstanding as of September 30, 2016	89,000	$	25.19

Stock-based compensation expense

	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Research and development	$	623	$	47	$	1,577	$	74
General and administrative		995		111		2,617		169
	$	1,618	$	158	$	4,194	$	243