Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Summary of Difference Between Provision for Income Taxes and Amounts Computed by Applying Statutory Federal Income Tax Rate to Income Before Income Taxes

The difference between the Company’s provision for income taxes and the amounts computed by applying the statutory federal income tax rate to income before income taxes is as follows (in thousands):

	Year Ended December 31,
	2017			2016			2015
Tax provision derived by applying the federal statutory rate to income before income taxes	$	(9,260	)	$	(7,377	)	$	(3,841	)
Permanent differences and other		296			333			307
Federal tax credits		(1,294	)		(1,921	)		(321	)
State tax credits		(284	)		(404	)		—
Change in tax rate		7,869			—			—
Conversion of LLC from partnership to corporation		—			—			(21	)
Change in the valuation allowance		2,673			9,369			3,876
Income tax expense /(benefit)	$	—		$	—		$	—

Components of Deferred Tax Assets and Liabilities

The components of the deferred tax assets and liabilities consist of the following (in thousands):

	December 31,
	2017			2016
Deferred tax assets
Net operating loss carryforward	$	12,170		$	12,286
Intangible assets		29			38
Accrued expense		333			335
Stock-based compensation		386			283
Federal tax credits		5,572			3,291
State tax credits		824			404
Other		75			76
Total deferred tax assets		19,389			16,713
Deferred tax liabilities
Depreciable assets	$	(63	)	$	(60	)
Total deferred tax liabilities		(63	)		(60	)
Less: Valuation allowance		(19,326	)		(16,653	)
Deferred tax assets, net	$	—		$	—