Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

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 three and six months ended June 30, 2019 and 2018 were as follows:

	Three months ended				Six months ended
	June 30,				June 30,
	2019		2018		2019		2018
Risk-free interest rates	1.89 - 2.41%		2.67 - 2.93%		1.89 - 2.67%		2.67 - 2.93%
Expected dividend yield	0.00%		0.00%		0.00%		0.00%
Expected term (in years)		6.0		6.0		6.0		6.0
Expected volatility	68.6 - 68.9%		69.8 - 70.4%		68.6 - 69.5%		69.8 - 71.5%

Summary of Stock Option Activity

The following table summarizes stock option activity for the six months ended June 30, 2019:

(In thousands, except per share amounts)	Shares Issuable Under Options			Weighted Average Exercise Price Per Share
Outstanding as of December 31, 2018		4,435		$	19.21
Granted		825			13.87
Exercised		—			7.15
Cancelled		(288	)		20.91
Outstanding as of June 30, 2019		4,972		$	18.23
Options vested and expected to vest at June 30, 2019		4,972		$	18.23
Options exercisable at June 30, 2019		2,911		$	18.03

Summary of of RSU Activity

The following table summarizes the RSU activity for the six months ended June 30, 2019:

(In thousands, except per share amounts)	Number of Shares			Weighted Average Grant Date Fair Value Per Share
Nonvested balance as of December 31, 2018		252		$	22.25
Granted		804			14.64
Vested/Released		(54	)		22.96
Cancelled		(87	)		16.11
Nonvested Balance as of June 30, 2019		915		$	16.11

Stock-Based Compensation Expense Related to Stock Options, and RSUs and Shares Purchased Under Employee Stock Purchase Plan

The Company recorded stock-based compensation expense related to stock options and RSUs and shares purchased under the Employee Stock Purchase Plan for the three and six months ended June 30, 2019 and 2018 as follows:

	For the three months ended June 30,				For the six months ended June 30,
(In thousands)	2019		2018		2019		2018
Research and development	$	1,385	$	1,137	$	2,541	$	2,287
Selling, general and administrative		2,832		2,847		5,529		5,354
Total	$	4,217	$	3,984	$	8,070	$	7,641