Equity Incentive Plans (Tables)

9 Months Ended

Sep. 30, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Options

The following table summarizes stock option activity for the nine months ended September 30, 2016:

	Options Outstanding
	Shares Available for Grant				Number of Options			Weighted- Average Exercise Price		Aggregate Intrinsic Value
										(In thousands)
Balance—December 31, 2015		4,810,271				9,931,229		$	5.29	$	229,591
Authorized		2,543,513
RSUs granted, net		(660,800	)
Granted		(1,165,660	)			1,165,660			12.84
Exercised		—				(457,654	)		1.03
Canceled		43,370		⁽¹⁾		(94,328	)		15.45
Balance—September 30, 2016		5,570,694				10,544,907		$	6.22	$	87,430
Options exercisable—September 30, 2016						5,569,984		$	3.24	$	56,838
Options vested and expected to vest—September 30, 2016						10,293,961		$	6.11	$	86,148

⁽¹⁾	This excludes 50,958 canceled options for the nine months ended September 30, 2016 initially granted from the legacy stock option plans. As these plans have been terminated, any options canceled are not added back to the existing option plan pool.

Summary of Restricted Stock Unit Activity

The following table summarizes restricted stock unit activity for the nine months ended September 30, 2016:

	RSUs Outstanding
	Number of Restricted Stock Units			Weighted- Average Grant Date Fair Value Per Share		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
								(In thousands)
Balance—December 31, 2015		—		$	—		—	$	—
Granted		662,800			14.29
Vested		—
Canceled/forfeited		(2,000	)		14.29
Balance—September 30, 2016		660,800		$	14.29		2.45	$	8,214

Summary of Stock-Based Compensation

Total stock-based compensation expense recognized was as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Research and development	$	2,257	$	499	$	6,226	$	1,250
General and administrative		1,527		1,388		4,626		3,982
Total stock-based compensation expense	$	3,784	$	1,887	$	10,852	$	5,232

Schedule of Black-Scholes Option-Pricing Model

The fair value of stock option awards granted to employees was estimated at the date of grant using a Black-Scholes option-pricing model with the following assumptions for the nine months ended September 30, 2016:

	2015 Plan		2015 ESPP
	Nine Months Ended September 30,		Nine Months Ended September 30,
	2016	2015	2016		2015
Expected term (in years)	5.31 - 6.05	5.30 - 6.10	0.5		0.5
Volatility	72.0 -75.0%	70.2 - 82.8%		73.8%		71.7%
Risk-free interest rate	1.25 - 1.72%	1.38 - 1.93%		0.36%		0.10%
Dividend yield	—%	—%	—%		—%