Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2015

The fair value of the stock options granted was estimated based on the following weighted average assumptions for three months ended March 31, 2015 and 2014:

	Three Months Ended March 31,
	2015			2014
Dividend yield		0	%		0	%
Expected volatility		82	%		94	%
Risk-free interest rate		1.34	%		1.73	%
Expected term	5.6 years			5.6 years

Stock option activity

Stock option activity for the three months ended March 31, 2015 was as follows:

	Options			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2015		7,702,309		$	8.15
Granted		1,322,528			3.82
Exercised		(65,815	)		1.55
Forfeited, expired or cancelled		(620,440	)		25.65
Outstanding at March 31, 2015		8,338,582		$	6.22		7.50	$	3,174
Vested and expected to vest at March 31, 2015		7,928,331		$	6.30		7.41	$	3,131
Exercisable at March 31, 2015		4,621,508		$	7.52		6.34	$	2,409

Unvested RSU activity

Unvested RSU activity for the three months ended March 31, 2015 is summarized below:

	Number of Shares			Weighted- Average Grant- Date Fair Value
Unvested balance at January 1, 2015		1,953,879		$	5.46
Granted		1,401,652			3.83
Vested		(802,081	)		5.04
Forfeited		(27,138	)		5.88
Unvested balance at March 31, 2015		2,526,312		$	4.69

Stock-based compensation expense

The following table shows allocated stock-based compensation expense included in the condensed consolidated statements of comprehensive loss for the three months ended March 31, 2015 and 2014 (in thousands):

	Three Months Ended March 31,
	2015		2014
Research and development	$	2,196	$	2,406
Selling, general and administrative		1,469		1,518
Total stock-based compensation expense	$	3,665	$	3,924