Stock Based Compensation (Tables)

12 Months Ended

Dec. 31, 2014

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

Summary of Total Stock-Based Compensation Expense

Total stock-based compensation expense was allocated to research and development, manufacturing and production and general and administrative expense as follows (in thousands):

	Year ended December 31,
	2014		2013		2012
Research and development	$	785	$	908	$	1,035
Manufacturing and production		229		258		207
General and administrative		2,145		2,300		2,048
Total stock-based compensation expense	$	3,159	$	3,466	$	3,290
Cash received from RSU grants and options exercised	$	2	$	816	$	221

Summary of Stock Option Transactions under Company's Stock Incentive Plans

The following table summarizes stock option transactions under the Company’s stock incentive plans for the years ended December 31, 2014, 2013 and 2012:

	Shares			Weighted Average Exercise Price
Outstanding December 31, 2011		6,955,100		$	3.51
Granted		1,687,257		$	3.50
Exercised		(96,345	)	$	2.29
Forfeited		(549,443	)	$	5.94
Outstanding December 31, 2012		7,996,569		$	3.36
Granted		2,876,382		$	2.56
Exercised		(347,450	)	$	2.34
Forfeited		(2,121,313	)	$	3.27
Outstanding December 31, 2013		8,404,188		$	3.15
Granted		1,889,614		$	1.40
Exercised		—		$	—
Forfeited		(1,699,370	)	$	3.69
Outstanding December 31, 2014		8,594,432		$	2.66
Vested and unvested options expected to vest as of December 31, 2014		8,188,766		$	2.70

Summary of Outstanding RSUs

A summary of the outstanding RSUs as of December 31, 2014, and changes during the year then ended is presented below:

	Shares			Weighted Average Grant-Date Fair Value per Share
Unvested at December 31, 2013		496,397		$	2.59
Granted		828,000		$	1.42
Vested		(346,164	)	$	2.30
Cancelled		(18,167	)	$	1.58
Unvested at December 31, 2014		960,066		$	1.70