STOCKHOLDERS' EQUITY AND SHARE-BASED COMPENSATION EXPENSE (Tables)

9 Months Ended

Sep. 30, 2013

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Share-based compensation expense

The Company recognized share-based compensation expense as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2013		2012		2013		2012
Costs of product sales	$	223	$	403	$	651	$	1,114
Research and development	340		307		906		980
Selling, general and administrative	1,436		1,549		3,552		12,763
Total share-based compensation expense	$	1,999	$	2,259	$	5,109	$	14,857

Fair value of options estimated at the date of grant with weighted-average assumptions

The fair value of options was estimated at the date of grant using the Black Scholes Merton option pricing model with the following weighted‑average assumptions:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2013		2012		2013		2012
Risk free interest rate	1.4	%	0.6	%	1.0	%	0.6	%
Expected dividend yield	0.0	%	0.0	%	0.0	%	0.0	%
Expected volatility	68	%	67	%	68	%	67	%
Expected option term (in years)	4.6		4.6		4.6		4.6

Assumptions Used to Value Employees Stock Purchase Rights

During the three and nine months ended September 30, 2013 and 2012, the fair value of shares under the ESPP was estimated using the following assumptions:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2013		2012		2013		2012
Risk free interest rate	0.1	%	0.1	%	0.1	%	0.1	%
Expected dividend yield	0.0	%	0.0	%	0.0	%	0.0	%
Expected volatility	52.6	%	67	%	52.6	%	67	%
Expected term (in years)	0.6		0.8		0.6		0.8