Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

The components of loss before income taxes consist of the following (in thousands):

The income tax expense consisted of the following (in thousands):

The following is a reconciliation of the statutory federal income tax rate to the Company’s effective tax rate:

	Years Ended December 31,
	2018			2017			2016
U.S. federal income tax at statutory rate		21.0	%		34.0	%		34.0	%
U.S. state and local income taxes		(1.3	)		(0.2	)		(0.1	)
Change in valuation allowance		(1,039.4	)		19.0			(36.9	)
Federal research and development tax credit		166.2			5.2			4.8
Convertible preferred stock warrants		-			(21.7	)		0.7
Stock-based compensation		859.4			1.2			(2.5	)
Meals and Entertainment		(6.6	)		(1.1	)		(0.2	)
Permanent items		(1.1	)		—			—
Foreign rate differential		(1.5	)		0.2			—
Tax rate change		2.4			(36.4	)		—
Provision to return trueup		5.9			—			—
Other		0.1			(0.7	)		(0.2	)
Effective tax rate		5.1	%		(0.5	)%		(0.4	)%

Significant components of the Company’s deferred income tax assets and liabilities consist of the following (in thousands):

	As of December 31,
	2018			2017
Deferred tax assets:
Net operating loss carryforwards	$	128,829		$	34,843
Reserves and accruals		7,840			13,577
Research and development credits		39,344			15,475
Depreciation and amortization		—			288
Stock-based compensation		7,529			4,098
Total deferred tax assets		183,542			68,281
Deferred tax liabilities:
Depreciation and amortization		(343	)		—
Total deferred tax liabilities		(343	)		—
Valuation allowance		(182,360	)		(68,219	)
Net deferred tax assets	$	839		$	62

A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):

	As of December 31,
	2018		2017
Unrecognized tax benefits at beginning of year	$	5,843	$	4,368
Gross increase for tax positions of current years		7,053		1,475
Gross increase for tax positions of prior year		1,645		—
Unrecognized tax benefits balance at end of year	$	14,541	$	5,843