Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2013

The following is a summary of option activity under the 2005 Plan and the 1995 Plan for the six months ended June 30, 2013:

	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		4,007,500		$	1.89		-		$	-
Exercised		(133,917	)	$	2.02		-		$	-
Canceled		(750,008	)	$	1.72		(23,750	)	$	4.05
Outstanding at June 30, 2013		12,267,400		$	1.88		188,150		$	5.04
Shares exercisable at June 30, 2013		4,662,956		$	2.17		188,150		$	5.04

Shares available for grant at June 30, 2013		2,518,619

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 June 30,		Six Months Ended June 30,
	2013	2012	2013	2012
Weighted-average fair value of stock options granted	$1.01	$0.71	$1.00	$0.71
Risk-free interest rate	0.54%-0.96%	0.59%	0.54%-1.34%	0.59%-1.54%
Dividend yield	0%	0%	0%	0%
Volatility	55.81%-66.02%	75.47%-75.52%	55.81%-73.72%	75.47%-80.48%
Expected term (in years)	3.98-4.25	4.24	3.98-7.05	3.34-7.09
Expected forfeiture rate	0%-23.15%	0%-23.15%	0%-23.15%	0%-23.15%

Summary of Restricted Stock Awards Activity

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

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

Stock-Based Compensation Expense

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2013		2012		2013		2012
Research and development	$	296	$	236	$	513	$	419
General and administrative		342		353		608		757
Total stock-based compensation expense	$	638	$	589	$	1,121	$	1,176