Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2012

Stock-Based Compensation

Schedule of stock option activity

	Shares		Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term (In Years)
Options Outstanding at December 31, 2011	4,459,034		$	6.08	6.9
Granted	1,115,700		$	5.84
Exercised	(21,679	)	$	2.61
Canceled	(201,056	)	$	8.22
Options Outstanding at September 30, 2012	5,351,999		$	5.97	7.2
Options Vested and Expected to Vest at September 30, 2012	5,273,241		$	5.98	7.1
Options Exercisable at September 30, 2012	3,190,776		$	6.77	5.9
Shares Available for Grant under the 2008 Plan	3,380,865

Schedule of stock-based compensation expense

	Three months ended September 30,				Nine months ended September 30,
	2012		2011		2012		2011
	(In thousands)
Research and development	$	330	$	327	$	1,010	$	1,032
General and administrative	195		243		604		671
Total stock-based compensation expense	$	525	$	570	$	1,614	$	1,703

Schedule of assumptions used for the fair values of employee stock options granted

	Three months ended September 30,				Nine months ended September 30,
	2012		2011		2012		2011
Expected stock price volatility	71	%	70	%	70 - 71	%	68 - 70	%
Expected option term	6.0 years		6.0 years		6.0 years		6.0 years
Risk-free interest rate	1.2 - 1.3	%	1.9 - 2.5	%	0.9 - 1.4	%	1.9 - 2.9	%
Expected dividend yield	None		None		None		None