Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2014

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, 2014 and 2013 are as follows:

($ in thousands)	Fair Value Measurements at Reporting Date Using
Description	Balance as of December 31, 2014		Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash equivalents	$	37,290	$	37,290	$	—	$	—
Warrant liability	$	—	$	—	$	—	$	—

($ 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	$	—

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)	2014		2013		2012
Research and development	$	1,416	$	792	$	1,917
General and administrative		3,327		2,715		2,963
Share based employee compensation expense before tax		4,743		3,507		4,880
Income tax benefit		—		—		—
Net share based employee compensation expense	$	4,743	$	3,507	$	4,880

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

The assumptions for volatility, expected life, dividend yield and risk-free interest rate are presented in the table below:

	2014	2013	2012
Weighted average risk-free interest rate	1.74 - 2.11%	1.00 - 2.10%	0.79 - 1.13%
Expected life in years	6	6	6
Expected volatility	85.22 - 94.55%	83.40 - 95.96%	83.36 - 83.53%
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, 2014, 2013, and 2012 consist of the following:

	December 31,
	2014		2013		2012
Stock options		6,505,664		6,747,303		7,147,303
Unvested restricted stock		144,508		352,865		733,739
Warrants		—		10,539,767		11,197,454
		6,650,172		17,639,935		19,078,496