Stock-Based Compensation

9 Months Ended

Sep. 30, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

8. Stock-Based Compensation

The Company classifies stock-based compensation expense in the accompanying condensed consolidated statements of operations and comprehensive loss based on the department to which a recipient belongs. The following table sets forth stock-based compensation expense related to options granted to employees and consultants for all periods presented (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Research and development	$	713	$	269	$	1,913	$	690
General and administrative		888		494		2,434		1,091
Total	$	1,601	$	763	$	4,347	$	1,781

The following summarizes option activity under the 2012 Equity Incentive Plan and 2015 Stock Option and Incentive Plan:

	Shares Subject to			Weighted Average
	Outstanding Options			Exercise Price Per Share
Balance at December 31, 2016		2,141,868		$	6.42
Options granted		1,685,575			14.69
Options exercised		(282,978	)		4.46
Options canceled		(254,788	)		9.13
Balance at September 30, 2017		3,289,677		$	10.62

In relation to stock options to purchase common stock that vest upon the achievement of performance criteria, the Company recorded zero and $174,000 in stock-based compensation expense for the three and nine months ended September 30, 2017, respectively, and $74,000 and $147,000 for the three and nine months ended September 30, 2016, respectively. The Company begins to recognize expenses related to these options during the period upon concluding that certain performance criteria are considered probable.