Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Stock-Based Compensation Expense Related to Equity Awards Granted to Employees and Consultants

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,
	2018		2017		2018		2017
Research and development	$	2,050	$	610	$	3,641	$	1,200
General and administrative		2,732		731		4,772		1,546
Total	$	4,782	$	1,341	$	8,413	$	2,746

Summary of Stock Option and Other Equity Award Activity Under Plans

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, 2017		2,964,549		$	11.54
Options granted		1,167,256			51.41
Options exercised		(263,145	)		7.31
Options canceled/forfeited		(99,248	)		20.26
Balance at June 30, 2018		3,769,412		$	23.95

	Shares Subject to			Weighted Average
	Outstanding Awards			Grant Date Fair Value
Balance at December 31, 2017		—		$	—
Restricted stock units granted		138,086			51.88
Restricted stock units forfeited		(2,830	)		53.77
Balance at June 30, 2018		135,256		$	51.84