Stock-Based Compensation

6 Months Ended

Jun. 30, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

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 June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
Research and development	$	610	$	247	$	1,200	$	421
General and administrative		731		357		1,546		597
Total	$	1,341	$	604	$	2,746	$	1,018

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		1,340,475		$	12.49
Options exercised		(15,281	)	$	1.66
Options canceled		(134,920	)	$	10.01
Balance at June 30, 2017		3,332,142		$	8.74

Pursuant to the terms of the Company’s 2015 Employee Stock Purchase Plan (the “2015 ESPP”), on April 28, 2017, the Company issued 36,429 shares to participants in the 2015 ESPP in exchange for their contributions during the period from November 1, 2016 to April 28, 2017.

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 six months ended June 30, 2017, respectively, and $73,000 for each of the three and six months ended June 30, 2016. The Company begins to recognize expenses related to these options during the period upon concluding that certain performance criteria are considered probable.