Stock-Based Compensation Expense (Tables)

3 Months Ended

Mar. 31, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Option Activity

The following table summarizes stock option activity during the three months ended March 31, 2016:

	Number of Options			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Life (in Years)		Weighted- Average Grant Date Fair Value
Outstanding as of December 31, 2015		2,369,847		$	13.99		8.28
Granted		945,480		$	7.91			$	5.88
Exercised		—		$	—
Canceled		(31,000	)	$	13.46
Outstanding as of March 31, 2016		3,284,327		$	12.23		8.52
Vested and expected to vest as of March 31, 2016		3,183,159		$	12.31		8.24
Vested and exercisable as of March 31, 2016		1,260,974		$	16.35		7.39

Summary of Stock-Based Compensation Expense

Stock-based compensation expense related to options granted was recorded as follows (in thousands):

	Three Months Ended March 31,
	2016		2015
Research and development	$	312	$	33
General and administrative		876		197
Total	$	1,188	$	230