Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Taxes [Abstract]

Schedule of Deferred Tax Assets and Liabilities

	As of December 31,
	2016			2015
	(in thousands)
Deferred tax assets:
Net operating loss carryforwards	$	258,405		$	263,138
Research and development tax credits	44,111			43,728
Orphan drug credits	24,233			—
Capitalized research and development	86,845			85,385
Stock-based compensation	7,060			8,160
Deferred revenue	39,307			4,363
Other	8,432			8,831
Total deferred tax assets	468,393			413,605
Deferred tax liabilities:
Deferred tax liability related to acquisition of Symphony Icon	(18,675		)	(18,675		)
Total deferred tax liabilities	(18,675		)	(18,675		)
Less: valuation allowance	(468,393		)	(413,605		)
Net deferred tax liabilities	$	(18,675	)	$	(18,675	)