STOCK-BASED COMPENSATION AND STOCK PLANS (Tables)

3 Months Ended

Mar. 31, 2016

Compensation and Retirement Disclosure [Abstract]

Schedule of stock-based compensation expense

	Three Months Ended March 31,
	2016		2015
Research and development	$	190	$	271
General and administrative		404		547
Total stock-based compensation expense	$	594	$	818

Schedule of activity of options under stock plans

Stock Options	Number of Shares			Weighted Average Exercise Price
Outstanding as of December 31, 2015		8,305,950		$	4.24
Granted		1,472,000			1.79
Exercised		(97,498	)		1.16
Cancelled		(203,254	)		3.95
Outstanding as of March 31, 2016		9,477,198		$	3.89
Exercisable as of March 31, 2016		6,383,542		$	4.93

Schedule of 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, 2016		9,304,672	$	3.89		5.7	$	452
Exercisable at March 31, 2016		6,383,542	$	4.93		4.1	$	102

Schedule of restricted stock activity

Restricted Stock	Number of Shares			Weighted Average Grant Date Fair Value
Unvested as of December 31, 2015		58,635		$	2.51
Vested		(29,306	)		2.51
Cancelled		(53	)		2.51
Unvested as of March 31, 2016		29,276		$	2.51