Equity Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2016

Summary of Activity Under 2008 Plan, 2014 Plan and Inducement Plan Including Grants to Nonemployees Issued

The following table summarizes activity under the 2008 Plan, the 2014 Plan, and the Inducement Plan, including grants to nonemployees issued:


				Options Issued and Outstanding
	Shares Available for Grant			Number of Shares			Weighted-Average Exercise Price per Share		Aggregate Intrinsic Value
									(in thousands)
Balance at December 31, 2013		3,914			1,162,829		$	1.03
Options authorized		1,452,661			—			—
Options granted		(188,888	)		188,888			24.41
Options exercised		—			(336,398	)		0.71
Options canceled		4,084			(4,084	)		2.21
Options repurchased		3,511			(3,511	)		0.55
Issuance of common stock for services		(10,000	)		—			—

Balance at December 31, 2014		1,265,282			1,007,724		$	5.51
Options authorized		743,569			—
Options granted		(379,709	)		379,709			19.60
Options exercised		—			(77,784	)		1.42
Options canceled		28,563			(28,563	)		12.41
Issuance of common stock for services		(13,285	)		—			—

Balance at December 31, 2015		1,644,420			1,281,086		$	9.78
Options authorized		1,038,595			—
Additional shares reserved under the Inducement Plan		1,000,000			—			—
Options granted		(1,524,014	)		1,524,014			11.42
Options exercised		—			(25,134	)		2.19
Options canceled		67,743			(67,743	)		16.67
Issuance of common stock for services		(20,118	)		—			—

Balance at December 31, 2016		2,206,626			2,712,223		$	10.60	$	13,750

Vested and expected to vest at December 31, 2016					2,640,905		$	10.54	$	13,574

Vested at December 31, 2016					1,263,430		$	7.58	$	10,187

Summary of Non-vested RSU Activity

A summary of non-vested RSU activity under the Plan for the year ended December 31, 2016 is as follows:


	Number of Shares			Weighted-Average Grant Date Fair Value Per Share
Non-vested restricted stock units at December 31, 2015		9,425		$	18.04
Granted		174,389			14.34
Vested		(30,122	)		16.35
Forfieted		(5,000	)		18.04

Non-vested restricted stock units at December 31, 2016		148,692		$	14.17

Summary of Weighted Average Assumptions to Estimate Fair Value of Stock Option Awards and Employee Stock Purchase Plan

The estimated grant date fair value of employee stock options was calculated using the Black-Scholes option-pricing model, based on the following weighted assumptions:


	Year Ended December 31,
	2016			2015			2014
Expected term ( years)		5.99			5.89			5.97
Volatility		77	%		75	%		94	%
Risk-free interest rate		1.62	%		1.64	%		1.79	%
Dividend yield		—	%		—	%		—	%

Summary of Stock-Based Compensation Recognized

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


	Year Ended December 31,
	2016		2015		2014
	(in thousands)
Research and development	$	2,786	$	1,327	$	1,376
General and administrative		2,531		1,307		316

Total stock-based compensation	$	5,317	$	2,634	$	1,692

2014 Employee Stock Purchase Plan [Member]

Summary of Weighted Average Assumptions to Estimate Fair Value of Stock Option Awards and Employee Stock Purchase Plan

The following table illustrates the weighted-average assumptions for the Black-Scholes option-pricing model used in determining the fair value of ESPP purchase rights granted to employees:


	Year Ended December 31, 2016
	2016			2015
Expected term ( years)		0.5			0.5
Volatility		76	%		97	%
Risk-free interest rate		0.48	%		0.16	%
Dividend yield		—	%		—	%