Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-based compensation expense includes amortization of stock options granted to employees and non-employees and has been reported in our Condensed Consolidated Statements of Operations and Comprehensive Loss as follows:



	Three Months Ended June 30,				Six Months Ended June 30,
	2016		2015		2016		2015
	(In thousands)				(In thousands)
Research and development	$	1,219	$	1,229	$	3,374	$	2,554
Selling, general and administrative	1,391		1,151		3,657		2,344
Total	$	2,610	$	2,380	$	7,031	$	4,898

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

The following assumptions were applied to employee and director stock option grants during the periods ended:



	Three Months Ended June 30,						Six Months Ended June 30,
	2016			2015			2016			2015
Estimated weighted-average fair value	$	8.50		$	12.63		$	6.93		$	12.97
Weighted-average assumptions
Expected volatility	74		%	69		%	74		%	70		%
Expected term, in years	5.8			5.9			5.7			5.9
Risk-free interest rate	1.37		%	1.71		%	1.40		%	1.61		%
Expected dividend yield	—		%	—		%	—		%	—		%

Stock Option Activity and Related Information

Stock option activity for all stock plans and related information is as follows:



	Options Outstanding		Weighted- Average Exercise Price per Share		Remaining Contractual Life (In years)	Aggregate Intrinsic Value (In thousands)
Balance at December 31, 2015	8,310,235		$	7.97
Granted	1,663,155		10.84
Exercised	(422,525	)	4.42
Forfeited	(49,047	)	14.02
Balance at June 30, 2016	9,501,818		$	8.60	6.44	$	23,678
Vested and expected to vest at June 30, 2016	9,225,654		$	8.51	6.36	$	23,615
Exercisable at June 30, 2016	6,764,948		$	7.41	5.45	$	23,051