Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Taxes

Schedule of reconciliation of effective income tax rate

A reconciliation of the income tax expense computed using the federal statutory income tax rate to the Company’s effective income tax rate is as follows:

	Year Ended
	December 31,
	2017		2016		2015
Income tax computed at federal statutory tax rate	34.0	%	34.0	%	34.0	%
State taxes, net of federal benefit	5.9	%	3.5	%	2.5	%
General business credit carryovers	2.5	%	1.5	%	0.8	%
Non-deductible expenses	(2.1)	%	(3.6)	%	(17.9)	%
Federal tax rate reduction	(24.7)	%	—	%	—	%
Change in valuation allowance	(15.6)	%	(35.4)	%	(19.4)	%
	—	%	—	%	—	%

Schedule of components of deferred tax assets and liabilities

The principal components of the Company’s deferred tax assets and liabilities consist of the following at December 31, 2017 and 2016 (in thousands):

	Year Ended
	December 31,
	2017		2016
Deferred tax assets:
Net operating loss carryforwards	$	27,726	$	16,490
Tax credit carryforwards		5,259		2,014
Accrued expenses		2,079		7,353
Capitalized patent costs		26,307		16,025
Deferred revenue		7,151		9,672
Construction financing lease obligation		9,352		13,685
Other		4,978		2,979
Total deferred tax assets		82,852		68,218
Less valuation allowance		(73,301)		(54,300)
Net deferred tax assets		9,551		13,918
Deferred tax liabilities—depreciation and amortization		(9,551)		(13,918)
Net deferred taxes	$	—	$	—