Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2013

Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]

Summary of Option Activity

	2005 Stock Incentive Plan					1995 Stock Option Plan
	Stock Options			Weighted-Average Exercise Price		Stock Options			Weighted-Average Exercise Price
Outstanding at January 1, 2013		9,143,825		$	1.87		211,900		$	4.94
Granted		4,117,500		$	1.92		-		$	-
Exercised		(522,292	)	$	2.29		-		$	-
Canceled		(802,883	)	$	1.74		(23,750	)	$	4.05
Outstanding at September 30, 2013		11,936,150		$	1.88		188,150		$	5.04
Shares exercisable at September 30, 2013		4,647,873		$	2.12		188,150		$	5.04
Shares available for grant at September 30, 2013		6,461,494

Assumptions used to Estimate Grant Date Fair Value of Stock Options granted using Black-Scholes Option-Pricing Model

The fair value of stock options granted was estimated at the date of grant using the Black-Scholes option-pricing model with the following assumptions:

	Three Months Ended September 30,						Nine Months Ended September 30,
	2013			2012			2013			2012
Weighted-average fair value of stock options granted	$	1.41		$	1.09		$	1.02		$	0.71
Risk-free interest rate		1.12%-1.36	%		0.55	%		0.54%-1.36	%		0.55%-1.54	%
Dividend yield		0	%		0	%		0	%		0	%
Volatility		56.75%-62.51	%		76.60%-76.71	%		55.81%-73.72	%		75.47%-80.48	%
Expected term (in years)		4.25			4.24			3.98-7.05			3.34-7.09
Expected forfeiture rate		23.15	%		23.15	%		0%-23.15	%		0%-23.15	%

Stock-Based Compensation Expense

The Company recorded stock-based compensation expense in the consolidated statements of operations as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2013		2012		2013		2012
Research and development	$	316	$	219	$	829	$	638
General and administrative		347		274		955		1,030
Total stock-based compensation expense	$	663	$	493	$	1,784	$	1,668

Summary of Restricted Stock Awards Activity

The following is a summary of restricted stock awards activity for the nine months ended September 30, 2013:

	Number of Shares		Per Share Weighted-Average Grant-Date Fair Value
Outstanding and Unvested at January 1, 2013		33,334	$	1.39
Restricted stock granted		-	$	-
Restricted stock vested		-	$	-
Restricted stock forfeited		-	$	-
Outstanding and Unvested at September 30, 2013		33,334	$	1.39

Employee Stock Purchase Plan [Member]

Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]

Assumptions used to Estimate Grant Date Fair Value of Stock Options granted using Black-Scholes Option-Pricing Model

The ESPP is considered compensatory for financial reporting purposes. As such, the fair value of ESPP shares was estimated at the date of grant using the Black-Scholes option-pricing model with the following assumptions:

	Three Months Ended September 30,
		2013
Weighted-average fair value of ESPP shares granted	$	0.78
Risk-free interest rate		0.04	%
Dividend yield		0	%
Volatility		50.80	%
Expected term (in years)		0.5
Expected forfeiture rate		5	%