Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2014

Summary of Share-based Compensation Expense

The following table summarizes all share-based compensation expense related to stock options, restricted stock and restricted stock units by expense category (in thousands):



	Three Months Ended March 31,
	2014		2013
Research and development
Stock options	$	8	$	396
Restricted stock	359		3
Research and development share-based compensation expense	367		399
General and administrative
Stock options	23		3,070
Restricted stock	2,308		9
Restricted stock units	—		52
General and administrative share-based compensation expense	2,331		3,131
Total share-based compensation expense included in expenses	$	2,698	$	3,530

Stock Options, Valuation Assumptions

The fair value of employee stock options was estimated at the grant date using the following assumptions:



	Three Months Ended March 31, 2014
Dividend yield	—
Volatility	132.0	%
Risk-free interest rate	1.85	%
Expected life of options (years)	6.11

Summary of Stock Option Activity and Related Data

A summary of the Company’s stock option activity and related data for the three months ended March 31, 2014 is as follows:



	Outstanding Options
	Number of Shares	Weighted-Average Exercise Price		Weighted Average Remaining Contractual Term (Years)
Balance at December 31, 2013	54,000	$	6.00	9.63
Granted	55,000	7.51		9.90
Balance at March 31, 2014	109,000	$	6.76	9.76