Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2012

Stock-Based Compensation [Abstract]

Stock-Based Compensation Expense on All Employee and Non-Employee Awards

The Company recognized stock-based compensation expense on all employee and non-employee awards as follows:

	For the three months ended September 30,				For the nine months ended September 30,
(in thousands)	2012		2011		2012		2011
Research and development	$	363	$	264	$	1,305	$	540
General and administrative		828		322		2,177		1,360
Stock-based employee compensation expense	$	1,191	$	586	$	3,482	$	1,900

Fair Value of Stock Options Assumptions Using Black-Scholes Option Valuation Model

For the three months ended September 30, 2012 and 2011, the fair value of stock options was estimated on the date of grant using a Black-Scholes option valuation model with the following assumptions:

	For the three months ended September 30,
	2012		2011
Risk-free interest rate		0.79 - 1.04%		1.12 - 2.61%
Expected life in years		6		5.77 - 6
Expected volatility		83.37 - 83.51%		83.26 - 87.4%
Expected dividend yield		0		0

Stock Option Activity Under Stock Option Plan

Stock option activity under the Company’s stock option plan for the nine months ended September 30, 2012 is as follows:

(in thousands, except share and per share data)	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Contractual   Term (Years)		Aggregate Intrinsic Value
Outstanding, December 31, 2011		5,138,486		$	4.08
Granted		508,700			5.07
Exercised		(8,300	)		3.61
Cancelled		(277,399	)		5.67
Outstanding, September 30, 2012		5,361,487		$	4.09		6.88	$	8,037
Vested and unvested expected to vest at September 30, 2012		5,262,835		$	4.09		6.88	$	7,889
Options exercisable, September 30, 2012		3,301,387		$	3.50		5.23	$	6,764
Options exercisable, December 31, 2011		2,911,186		$	3.21		5.52	$	4,232
Options available for future grant		3,594,700

Summary of Unvested Restricted Stock

A summary of the status of unvested restricted stock for the nine months ended September 30, 2012 is as follows:

	Number of Shares			Weighted-Average Grant Date Fair Value
Non-vested, December 31, 2011		950,906		$	4.34
Granted		170,302			4.51
Vested		(75,000	)		5.66
Cancelled		(123,370	)		4.34
Non-vested, September 30, 2012