Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

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,
	2017			2016			2015
	(in thousands)
United States	$	(42,425	)	$	(48,244	)	$	(53,376	)
International		566			520			171
Loss before provision for income taxes	$	(41,859	)	$	(47,724	)	$	(53,205	)

Components of Provision for Income Taxes

The components of the provision for income taxes are as follows:

	Year Ended December 31,
	2017			2016			2015
	(in thousands)
Current tax provision:
Federal	$	—		$	—		$	—
State		—			—			—
Foreign		183			170			59
Total current tax provision		183			170			59
Deferred tax provision (benefit):
Foreign		(27	)		(27	)		(4	)
Total deferred tax provision (benefit)	$	(27	)	$	(27	)	$	(4	)
Total provision for income taxes	$	156		$	143		$	55

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 income taxes is as follows:

	Year Ended December 31,
	2017			2016			2015
	(in thousands)
Federal statutory rate		34.0	%		34.0	%		34.0	%
Effect of:
Effect of ownership change on deferred tax assets		(84.8	)		—			—
Change in valuation allowance		69.5			(33.5	)		(27.8	)
US tax reform deferred impact of tax rate change		(17.3	)		—			—
Federal tax credit		(0.9	)		1.6			2.6
State income tax benefit, net of federal benefit		0.1			0.1			2.9
Change in fair value of preferred stock warrants		—			—			(11.1	)
Other permanent items		(1.0	)		(2.5	)		(0.7	)
Total provision for income taxes		(0.4	)%		(0.3	)%		(0.1	)%

Components of the Deferred Tax Assets

The components of the deferred tax assets are as follows:

	December 31,
	2017			2016
	(in thousands)
Deferred tax assets:
Net operating loss carryforwards	$	9,183		$	35,244
Stock Based Compensation		2,444			2,291
59 (e) expenditures and amortization		1,435			—
License fee		1,346			3,339
Research and development credits		365			2,597
Other		698			1,017
Gross deferred tax assets		15,471			44,488
Valuation allowance		(15,395	)		(44,440	)
Total deferred tax assets		76			48
Deferred tax liabilities:
Other		13			12
Total deferred tax liabilities		13			12
Total net deferred tax assets	$	63		$	36

Unrecognized Tax Benefits

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

	Year Ended December 31,
	2017			2016		2015
	(in thousands)
Beginning balance	$	311		$	232	$	162
Increases based on tax positions related to prior years		—			—		—
Decreases based on tax positions related to prior years		(79	)		—		(77	)
Decreases due to ownership change		(232	)		—		—
Increases based on tax positions in current year		43			79		147
Settlement		—			—		—
Lapse of statute of limitations		—			—		—
Ending balance	$	43		$	311	$	232