Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Schedule of Deferred Tax Assets and Liabilities

	As of December 31,
	2019		2018
	(in thousands)
Deferred tax assets:
Net operating loss carryforwards	$	193,270	$	206,789
Research and development tax credits	46,306		47,087
Orphan drug credits	24,524		24,524
Capitalized research and development	58,596		71,047
Stock-based compensation	5,340		4,641
Deferred revenue	—		5,458
Interest	—		3,625
Other	5,533		6,044
Total deferred tax assets	333,569		369,215
Deferred tax liabilities:
Deferred tax liability related to acquisition of Symphony Icon	(4,140)		(10,525)
Other	(3)		(2)
Total deferred tax liabilities	(4,143)		(10,527)
Less: valuation allowance	(329,426)		(364,702)
Net deferred tax liabilities	$	—	$	(6,014)

Schedule of Effective Income Tax Rate Reconciliation

A reconciliation of the statutory tax rate to the effective tax rate for the years ended December 31, 2019, 2018 and 2017 consists of the following:

	Year Ended December 31,
	2019		2018		2017
	(in thousands)
Expected income tax expense (benefit) at 21%, 21% and 35%, respectively	$	26,065	$	(25,315)	$	(47,479)
State income taxes, net of federal benefit	445		(809)		(2,324)
Equity compensation	1,688		1,059		1,447
Research and development credit	—		(978)		(1,993)
Orphan drug credit	—		—		(189)
Deferred true-up	—		—		(5,316)
Tax rate change	—		—		169,464
Symphony Icon fair value adjustment	—		—		735
Change in valuation allowance	(35,276)		25,928		(126,634)
Other (1)	1,064		115		(372)
Income tax benefit	$	(6,014)	$	—	$	(12,661)