Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2012

Stock-Based Compensation

Summary of stock option activity

	Shares			Weighted average exercise price		Weighted average remaining contractual life (years)		Aggregate intrinsic value
Outstanding at January 1		5,821,073		$	7.54
Options granted		1,799,096			5.14
Options exercised		(322,298	)		3.54
Options cancelled		(1,776,287	)		9.36
Outstanding at December 31		5,521,584		$	6.40		6.83	$	17,472,889
Exercisable at December 31		3,091,173		$	7.44		5.25	$	7,906,822

Summary unvested restricted shares

	Shares			Weighted average grant date fair value
Outstanding at January 1		82,450		$	4.94
Vested		(92,571	)		5.16
Granted		45,243			5.47
Outstanding at December 31		35,122		$	5.04

Schedule of weighted average assumptions used to estimate fair value of each employee stock option award

	Years ended December 31,
	2012			2011			2010
Risk-free interest rate		1.11	%		2.48	%		2.62	%
Expected life in years		6.25 years			6.25 years			6.25 years
Volatility		101	%		101	%		102	%
Expected dividend yield		—			—			—

Schedule of stock-based compensation expense

Stock-based compensation expense during the years ended December 31, 2012, 2011 and 2010 was as follows (in thousands):

	Years ended December 31,
	2012		2011		2010
Stock-based compensation expense by type of award:
Employee stock options	$	3,082	$	2,951	$	3,614
Restricted stock		240		403		434
Total stock-based compensation expense	$	3,322	$	3,354	$	4,048
Effect of stock-based compensation expense by line item:
Research and development	$	2,485	$	2,494	$	3,074
General and administrative		837		860		974
Total stock-based compensation expense included in net loss	$	3,322	$	3,354	$	4,048

Schedule of unrecognized stock-based compensation expense

Unrecognized stock-based compensation expense as of December 31, 2012 was as follows (in thousands):

	Unrecognized stock compensation expense as of December 31, 2012		Weighted average remaining period (in years)
Employee stock options	$	7,747		2.65
Restricted stock		172		0.62
Total	$	7,919		2.61