Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2014

Option Activity under Stock-Based Compensation Plans

Option activity under our stock-based compensation plans during the three months ended March 31, 2014 was as follows (in thousands except per share amounts):

	Shares Underlying Outstanding Options (in thousands)			Weighted-Average Exercise Price Per Share		Weighted-Average Remaining Contractual Term (years)		Aggregate Intrinsic Value (in thousands)
Balance at December 31, 2013		15,765		$	3.17
Options granted		4,890			1.71
Options exercised		-			-
Options cancelled:
Options forfeited (unvested)		(89	)		2.71
Options cancelled (vested)		(461	)		3.71
Balance at March 31, 2014		20,105			2.80		6.25	$	1,566
Vested and expected to vest at March 31, 2014		20,105			2.80		6.25	$	1,566
Exercisable at March 31, 2014		10,899			3.32		3.76	$	969

Summary of Restricted Stock Units Activity

Restricted stock unit activity under our stock-based compensation plans during the three months ended March 31, 2014 was as follows (in thousands except per share amounts):

	Number of Shares (In thousands)			Weighted-Average Grant-Date Fair Value
Non-vested as of December 31, 2013		1,275		$	3.93
Granted		1,505		$	1.80
Vested		-		$	-
Forfeited or expired		(1,000	)	$	4.22
Non-vested as of March 31, 2014		1,780		$	1.76

Fair Value-Based Measurements and Weighted-Average Assumptions

The fair value-based measurements and weighted-average assumptions used in the calculations of these measurements are as follows:

	Stock Options						Employee Stock Purchase Plan
	Three Months Ended						Three Months Ended
	March 31,						March 31,
	2014			2013			2014			2013
Weighted-average fair value	$	1.57		$	2.70		$	0.92		$	1.46
Risk-free interest rate		1.8	%		1.1	%		0.2	%		0.2	%
Expected life (in years)		5.9			5.8			1.1			1.3
Volatility		1.4			1.4			0.9			0.7

Stock-Based Compensation Expense

The components of stock-based compensation expense were (in thousands):

	Three Months Ended
	March 31,
	2014		2013
Research and development	$	692	$	1,323
General and administrative		578		2,943
Total	$	1,270	$	4,266