Stock Based Compensation

9 Months Ended

Sep. 30, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Based Compensation

7. Stock Based Compensation

A summary of stock option activity is as follows (in thousands, except weighted-average exercise price and contractual term amounts):

	Options Outstanding
	Number of Shares Underlying Outstanding Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)		Aggregate Value Intrinsic
Outstanding — December 31, 2017		3,571		$	7.67
Options granted		1,160		$	8.13
Options exercised		(125	)	$	1.97
Options cancelled		(72	)	$	8.09
Outstanding — September 30, 2018		4,534		$	7.94		7.79	$	3,001
Exercisable — September 30, 2018		2,329		$	7.97		6.94	$	1,946

Total stock-based compensation expense related to the Company’s 2010 Equity Incentive Plan, 2014 Equity Incentive Plan and the 2014 Employee Stock Purchase Plan was as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Research and development	$	1,013	$	766	$	3,021	$	2,115
General and administrative		803		699		2,596		1,853
Total stock-based compensation	$	1,816	$	1,465	$	5,617	$	3,968