Quarterly report pursuant to Section 13 or 15(d)

Stock Plans (Tables)

Stock Plans (Tables)

6 Months Ended

Jun. 30, 2013

Summary of stock-based compensation expense recorded for awards under the stock option plans

The following table summarizes the stock-based compensation expense recorded for awards under the stock option plans for the three and six month periods ended June 30, 2013 and 2012:


	Three Months Ended June 30,				Six Months Ended June 30,
(in thousands, except per share amounts)	2013		2012		2013		2012
Research and development	$	52	$	114	$	356	$	730
General and administrative		78		202		279		1,138

Total stock-based compensation expenses	$	130	$	316	$	635	$	1,868

Schedule of assumptions used to estimate the stock-based compensation expense

We use the Black-Scholes-Merton option-pricing model with the following assumptions to estimate the stock-based compensation expense for the three and six month periods ended June 30, 2013 and 2012:


	Three Months Ended June 30,						Six months Ended June 30,
	2013			2012			2013			2012
Weighted-average risk-free interest rate		1.0	%		0.7	%		0.8	%		0.9	%
Expected dividend payments		—			—			—			—
Expected holding period (years)¹		3.9			5.0			4.2			5.1
Weighted-average volatility factor²		1.56			1.78			1.70			1.74
Estimated forfeiture rates for options granted to management³		23	%		23	%		23	%		23	%
Estimated forfeiture rates for options granted to non-management³		41	%		41	%		41	%		41	%

(1)	Expected holding periods are based on the simplified method provided in Staff Accounting Bulletin No. 107 for “plain vanilla options.”

(2)	Weighted average volatility is based on the historical volatility of our common stock.

(3)	Estimated forfeiture rates are based on historical data.

Summary of option activity

The following table summarizes option activity for the six month period ended June 30, 2013:


(in thousands, except per share amounts)	Options			Weighted Average Exercise Price		Weighted Average Remaining Option Term		Aggregate Intrinsic Value
Outstanding at January 1, 2013		6,842		$	1.33		6.65	$	722
Granted		—			—
Exercised		(75	)		1.50
Expired or cancelled		—			—
Forfeited		—			—

Outstanding at June 30, 2013		6,767		$	1.32		6.22	$	—

Exercisable at June 30, 2013		6,743		$	1.32		6.22	$	—