Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Schedule of Geographical Breakdown of Loss Before Provision for Income Taxes

The geographical breakdown of loss before provision for income taxes is as follows:

	Year Ended December 31,
	2018			2017			2016
	(in thousands)
United States	$	(54,395	)	$	(42,425	)	$	(48,244	)
International		758			566			520
Loss before provision for (benefit from) income taxes, net	$	(53,637	)	$	(41,859	)	$	(47,724	)

Components of Provision (Benefit from) for Income Taxes

The components of the provision for (benefit from) income taxes are as follows:

	Year Ended December 31,
	2018			2017			2016
	(in thousands)
Current tax provision (benefit):
Federal	$	—		$	—		$	—
State		—			—			—
Foreign		(180	)		183			170
Total current tax provision (benefit)		(180	)		183			170
Deferred tax provision (benefit):
Foreign		(122	)		(27	)		(27	)
Total deferred tax provision (benefit)	$	(122	)	$	(27	)	$	(27	)
Total provision for (benefit from) income taxes	$	(302	)	$	156		$	143

Reconciliation Between Income Taxes Computed at the Federal Statutory Income Tax Rate and the Provision for Income Taxes

The reconciliation between income taxes computed at the federal statutory income tax rate and the provision for (benefit from) income taxes is as follows:

	Year Ended December 31,
	2018			2017			2016
Federal statutory rate		21.0	%		34.0	%		34.0	%
Effect of:
Change in valuation allowance		(22.2	)		69.5			(33.5	)
Federal Tax Credit		2.4			(0.9	)		1.6
State income tax benefit, net of federal benefit		0.3			0.1			0.1
Effect of ownership change on deferred tax assets		—			(84.8	)		—
US tax reform deferred impact on tax rate change		—			(17.3	)		—
Other permanent items		(1.0	)		(1.0	)		(2.5	)
Total provision for (benefit from) income taxes		0.5	%		(0.4	)%		(0.3	)%

Components of the Deferred Tax Assets

The components of the deferred tax assets are as follows:

	December 31,
	2018			2017
	(in thousands)
Deferred tax assets:
Net operating loss carryforwards	$	18,347		$	9,183
Stock based compensation		3,642			2,444
License fee		2,008			1,346
59 (e) expenditures and amortization		1,435			1,435
Research and development credits		1,137			365
Other		972			698
Gross deferred tax assets		27,541			15,471
Valuation allowance		(27,317	)		(15,395	)
Total deferred tax assets		224			76
Deferred tax liabilities:
Other		39			13
Total deferred tax liabilities		39			13
Total net deferred tax assets	$	185		$	63

Unrecognized Tax Benefits

The activity related to the gross amount of unrecognized tax benefits is as follows:

	Year Ended December 31,
	2018		2017			2016
	(in thousands)
Beginning balance	$	43	$	311		$	232
Increases based on tax positions related to prior years		109		—			—
Decreases based on tax positions related to prior years		—		(79	)		—
Decreases due to ownership change		—		(232	)		—
Increases based on tax positions in current year		112		43			79
Settlement		—		—			—
Lapse of statute of limitations		—		—			—
Ending balance	$	264	$	43		$	311