Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Taxes

Schedule of reconciliation of U.S. statutory income tax rate to effective tax rate

	Year Ended December 31,
	2016			2015			2014
Federal income tax (benefit) at statutory rate		34.00	%		34.00	%		34.00	%
Permanent differences		(0.85	)		(0.86	)		(1.29	)
Federal research and development credits and adjustments		2.43			2.64			2.70
State income tax, net of federal benefit		5.70			5.77			6.03
Other		(0.40	)		0.28			(0.15	)
Change in valuation allowance		(40.88	)		(41.82	)		(41.29	)
Effective income tax rate		—	%		—	%		—	%

Schedule of components of deferred tax assets

        The Company's deferred tax assets consisted of the following (in thousands):

	Year Ended December 31,
	2016			2015
Deferred tax assets
Net operating loss carryforwards	$	48,682		$	35,042
Tax credit carryforwards		4,833			3,762
Capitalized research and development		3,394			4,087
Capitalized legal expenses		1,597			1,464
Other differences		1,335			815
Total deferred tax assets		59,841			45,170
Valuation allowance		(59,841	)		(45,170	)
Net deferred tax assets	$	—		$	—