Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Significant Component of Deferred Tax Assets

Significant components of the Company’s deferred tax assets at December 31, 2018 and 2017 are as follows:

	December 31,
(in thousands)	2018			2017
Net operating loss carryforwards	$	106,430		$	89,098
Start-up and organizational costs		33,977			37,488
Research and development credit carryforwards		33,684			32,395
Stock compensation		990			1,330
Capitalized acquisition costs		5,160			5,822
Deferred revenue		—			11,126
Depreciation		132			136
Other		920			993
		181,293			178,388
Less valuation allowance		(181,293	)		(178,388	)
Effective tax rate	$	—		$	—

Reconciliation of Income Tax Expense (Benefit)

A reconciliation of income tax expense (benefit) at the statutory federal income tax rate and income taxes as reflected in the financial statements is as follows:

	Year Ended December 31,
(in thousands)	2018			2017			2016
Federal income tax at statutory rates		21	%		34	%		34	%
State income tax, net of federal tax benefit		4	%		4	%		1	%
Research and development credits		2	%		3	%		3	%
Stock compensation		-1	%		-1	%		-1	%
Channel rights		0	%		0	%		-25	%
Research and development true-up		0	%		-7	%		0	%
Officers compensation		-1	%		-2	%		0	%
Other		-2	%		-3	%		0	%
Federal rate change		3	%		-124	%		0	%
Change in valuation allowance		-26	%		96	%		-12	%
Effective tax rate		0	%		0	%		0	%