Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Taxes

Schedule of components of the net deferred tax asset

The components of the net deferred tax asset are as follows (in thousands):

	December 31,
	2016		2015
Gross deferred tax assets:
Net operating loss carryforwards	$	48,654	$	37,051
Accrued expenses		55		29
Contributions		6		6
Deferred expenses		58		23
Stock-based compensation		1,523		826
Research and development and other credits		5,258		4,123
Total gross deferred tax assets		55,554		42,058
Gross deferred tax liabilities:
Depreciation		(3)		(2)
Total gross deferred tax liabilities		(3)		(2)
Net deferred tax assets		55,551		42,056
Less: valuation allowance		(55,551)		(42,056)
Net deferred tax assets after valuation allowance	$	—	$	—

Schedule of reconciliation of income tax expense (benefit) at the statutory federal income tax rate and income taxes

	Year Ended December 31,
	2016		2015		2014
Federal income tax expense at statutory rate	34.0	%	34.0	%	34.0	%
Permanent items	(1.2)		(1.0)		(5.4)
State income tax, net of federal benefit	7.5		7.1		3.8
R&D tax credits	5.2		4.2		4.2
Other	1.6		5.0		—
Change in valuation allowance	(47.1)		(49.3)		(36.6)
Effective income tax rate	0.0	%	0.0	%	0.0	%