Stock-Based Compensation

6 Months Ended

Jun. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

9. 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 equity awards granted to employees and consultants for all periods presented (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Research and development	$	3,795	$	2,050	$	6,758	$	3,641
Selling, general and administrative		4,843		2,732		8,861		4,772
Total	$	8,638	$	4,782	$	15,619	$	8,413

The following summarizes option and other equity award 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, 2018		3,701,461		$	26.40
Options granted		1,179,253			41.34
Options exercised		(88,629	)		11.23
Options canceled/forfeited		(71,235	)		32.24
Balance at June 30, 2019		4,720,850			30.33
	Shares Subject to			Weighted Average
	Outstanding Awards			Grant Date Fair Value
Balance at December 31, 2018		162,946		$	53.37
RSUs awarded		460,149			41.54
RSUs released		(32,523	)		52.06
RSUs forfeited		(8,154	)		47.25
Balance at June 30, 2019		582,418			44.19

Restricted stock units (“RSUs”) settle into shares of common stock upon vesting and the fair value is the market price on the date of grant.

Pursuant to the terms of the Company’s 2015 Employee Stock Purchase Plan (the “2015 ESPP”), on April 30, 2019, the Company issued 20,958 shares to participants in the 2015 ESPP in exchange for their contributions during the period from November 1, 2018 to April 30, 2019.

In relation to stock options and awards that vest upon the achievement of performance criteria, there was $0 and $40,000 in stock-based compensation expense recorded for the three months ended June 30, 2019 and 2018, respectively, and $0 and $193,000 was recorded for the six months ended June 30, 2019 and 2018, respectively. The Company begins to recognize expenses related to these stock options and awards during the period upon concluding that certain performance criteria are considered probable.