STOCK-BASED COMPENSATION AND STOCK PLANS (Tables)

3 Months Ended

Mar. 31, 2013

Compensation and Retirement Disclosure [Abstract]

Schedule of stock-based compensation expense

	Three Months Ended March 31,
	2013		2012
Research and development	$	494		$	460
General and administrative		871			738
Total stock-based compensation expense	$	1,365		$	1,198

Schedule of activity of options under stock plans

Stock Options	Number of Shares			Weighted Average Exercise Price
Outstanding as of December 31, 2012		7,157,458		$	5.70
Granted		1,120,910			2.51
Exercised		—			—
Cancelled		(18,765	)		3.23
Outstanding as of March 31, 2013		8,259,603		$	5.27
Exercisable as of March 31, 2013		5,235,700		$	5.33

Schedule of details regarding shares vested, expected to vest and exercisable

	Shares	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Vested and unvested expected to vest at March 31, 2013	8,112,241	$	5.27	6.4	$	88
Exercisable at March 31, 2013	5,235,700	$	5.33	5.1	$	3

Schedule of activity of restricted stock under the plan

Restricted Stock	Number of Shares			Weighted Average Grant Date Fair Value
Unvested as of December 31, 2012		79,795		$	3.54
Granted		242,697			2.51
Vested		(79,795	)		3.54
Cancelled		—			—
Unvested as of March 31, 2013		242,697		$	2.51