Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Schedule of Reconciliation of Effective Income Tax Expense (Benefit)

A reconciliation of income tax expense (benefit) computed at the statutory federal income tax rate of 34 percent to income tax expense (benefit) as reflected in the financial statements is as follows (in thousands):

	Years Ended December 31,
	2016			2015			2014
Federal income tax benefit at statutory rate	$	(21,556	)	$	(7,756	)	$	(1,089	)
State income tax benefit, net of federal benefit		(1,617	)		(1,511	)		(264	)
Change in income tax rates upon conversion to C-corporation		—			—			427
Federal deferred tax assets upon conversion to C-corporation		—			—			(105	)
Step-up in assets upon conversion to C-corporation		—			(709	)		(448	)
Research and development credits		(7,275	)		—			—
Stock-based compensation expense for incentive stock options and employee stock purchase plan		1,805			283			98
Other non-deductible expenses and reconciling items		212			240			129
Change in valuation allowance		27,996			9,453			1,252
Total income tax expense (benefit)	$	(435	)	$	—		$	—

Components of Net Deferred Tax Assets

The significant components of the Company’s net deferred tax assets are as follows (in thousands):

	December 31, 2016			December 31, 2015
Deferred tax assets:
Net operating loss carryforwards	$	25,625		$	9,254
Research and development tax credits		10,890			—
Step-up in assets upon conversion to C-corporation		953			1,046
Stock-based compensation expense for non-qualified stock options and restricted stock units		1,401			855
Unrealized losses on marketable securities		—			284
Deferred rent		258			97
Accruals and other		1,132			568
Total deferred tax assets before valuation allowance		40,259			12,104
Valuation allowance		(40,084	)		(12,093	)
Total deferred tax assets		175			11
Deferred tax liabilities:
Depreciation		(19	)		(11	)
Unrealized gains on marketable securities		(156	)		—
Total deferred tax liabilities		(175	)		(11	)
Net deferred tax assets	$	—		$	—