Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Relevant Data Used to Estimate Fair Value of Stock Option Grants

The relevant data used to determine the value of the stock option grants for the six months ended June 30, 2017 and 2016 are as follows:

	Six months ended June 30,
	2017			2016
Risk-free interest rates	1.97-2.29%			1.08-1.90%
Expected dividend yield		0.00	%		0.00	%
Expected term (in years)		6.0			6.0
Expected volatility	69.9-72.8%			79.8-87.9%

Summary of Stock Option Activity

The following table summarizes stock option activity for the six months ended June 30, 2017:

(In thousands, except per share amounts)	SharesIssuable UnderOptions			WeightedAverage ExercisePrice
Outstanding as of December 31, 2016		3,268		$	14.84
Granted		879			22.03
Exercised		(182	)		8.01
Cancelled		(89	)		17.17
Outstanding as of June 30, 2017		3,876		$	17.60
Options vested and expected to vest at June 30, 2017		3,876		$	17.60
Options exercisable at June 30, 2017		1,353		$	14.15

Stock-Based Compensation Expense Related to Stock Options

The Company recorded stock-based compensation expense related to stock options for the three and six months ended June 30, 2017 and 2016 as follows:

	Three months ended June 30,				Six months ended June 30,
(In thousands)	2017		2016		2017		2016
Research and development	$	923	$	576	$	1,802	$	1,113
General and administrative		1,440		1,043		2,939		2,147
	$	2,363	$	1,619	$	4,741	$	3,260