Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2013

Assets and Liabilities Measured at Fair Value on Recurring Basis

Assets and liabilities measured at fair value on a recurring basis as of December 31, 2013 and 2012 are as follows:

($ in thousands)			Fair Value Measurements at Reporting Date Using
Description	Balance as of December 31, 2013		Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents	$	66,794	$	66,794	$	—	$	—
Warrant liability	$	11,776	$	—	$	11,776	$	—

($ in thousands)			Fair Value Measurements at Reporting Date Using
Description	Balance as of December 31, 2012		Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents	$	72,002	$	72,002	$	—	$	—
Warrant liability	$	12,962	$	—	$	12,962	$	—

Share-Based Compensation Expense Included in Statements of Operations

The following table presents share-based compensation expense included in the Company’s Statements of Operations:

	Year ended December 31,
(in thousands)	2013		2012		2011
Research and development	$	792	$	1,917	$	890
General and administrative		2,715		2,963		1,869
Share based employee compensation expense before tax		3,507		4,880		2,759
Income tax benefit		—		—		—
Net share based employee compensation expense	$	3,507	$	4,880	$	2,759

Effect on Net Loss and Earnings Per Share if Applied Fair Value Recognition Provisions to Stock-Based Awards

The following table illustrates the effect on net loss and earnings per share if the Company had applied the fair value recognition provisions of current accounting standards to stock-based awards from September 9, 2003 (date of inception) to December 31, 2005:

(in thousands, except per share data)	September 9, 2003 (date of inception) to December 31, 2005
Net loss:
As reported	$	(15,364	)
Stock-based compensation expense included in reported net loss		802
Stock-based compensation expense under the fair-value based method		(1,756	)
Pro forma net loss	$	(16,318	)
Basic and diluted net loss per share:
As reported	$	(3.75	)
Pro forma	$	(3.98	)

Assumptions for Volatility, Expected life, Dividend Yield and Risk-free Interest Rate

and No. 110. The assumptions for volatility, expected life, dividend yield and risk-free interest rate are presented in the table below:

	2013	2012	2011
Weighted average risk-free interest rate	1.00 - 2.10%	0.79 - 1.13%	1.09 - 2.69%
Expected life in years	6	6	6
Expected volatility	83.40 - 95.96%	83.36 - 83.53%	83.26 - 87.29%
Expected dividend yield	0	0	0

Potential Dilutive Shares Excluded from Computation of Diluted Net Loss Per Share

The Company’s potential dilutive shares, which include outstanding common stock options, unvested restricted stock and warrants, have not been included in the computation of diluted net loss per share for any of the periods presented as the result would be antidilutive. Such potential common shares at December 31, 2013, 2012, and 2011 consist of the following:

	December 31,
	2013		2012		2011
Stock options		6,747,303		7,147,303		5,138,486
Unvested restricted stock		352,865		733,739		950,906
Warrants		10,539,767		11,197,454		13,117,264
		17,639,935		19,078,496		19,206,656