INCOME TAXES (Tables)

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Analysis of Deferred Tax Assets

An analysis of the deferred tax assets is as follows: 

	As of December 31,
	2016			2015
	(in thousands)
Net operating loss carryforwards	$	174,569		$	138,786
Difference in depreciation and amortization		2,589			2,694
Research and development tax credits		37,812			31,397
Stock-based compensation		16,166			20,774
Deferred rent		2,306			2,771
Deferred revenue		1,315			1,324
Capitalized inventory		36,282			19,018
Other		3,047			3,060
Gross deferred tax assets		274,086			219,824
Valuation allowance		(274,086	)		(219,824	)
Net deferred tax assets	$	—		$	—

Reconciliation Between Effective Tax Rate and Income Tax Rate

The reconciliation between the Company’s effective tax rate and the income tax rate is as follows:

	For the Year Ended December 31,
	2016				2015				2014
Federal income tax rate		34.0		%		34.0		%		34.0		%
Research and development tax credits		1.5				0.3				2.4
Valuation allowance		(17.3	)			(19.1	)			(21.6	)
Permanent Differences		(3.4	)			(1.7	)			(2.4	)
Foreign rate differential		(14.8	)			(13.5	)			(12.4	)
Effective tax rate		—		%		—		%		—		%

Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits

The reconciliation of the beginning and ending amount of total unrecognized tax benefits for the years ended December 31, 2016, 2015 and 2014 are as follows:

	For the Year Ended December 31,
	2016		2015		2014
	(in thousands)
Balance at beginning of the period	$	3,706	$	—	$	—
Increase related to current year tax positions		801		613		—
Increase related to prior year tax positions		137		3,093		—
Balance at end of the period	$	4,644	$	3,706	$	—