Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Taxes

Summary of loss before income taxes

	Year Ended December 31,
	2018		2017		2016
U.S. operations	$	7,855	$	8,347	$	28,643
Foreign operations		28,871		10,551		—
Loss before income taxes	$	36,726	$	18,898	$	28,643

Schedule of components of the net deferred tax asset

The components of the net deferred tax asset are as follows (in thousands):

	December 31,
	2018		2017
Gross deferred tax assets:
Net operating loss carryforwards	$	36,383	$	35,559
Accrued expenses		52		52
Contributions		3		4
Deferred expenses		—		35
Stock‑based compensation		1,640		1,459
Research and development and other credits		6,545		5,536
Total gross deferred tax assets	$	44,623	$	42,645
Gross deferred tax liabilities:
Depreciation		(18)		(17)
Total gross deferred tax liabilities		(18)		(17)
Net deferred tax assets		44,605		42,628
Less: valuation allowance		(44,605)		(42,628)
Net deferred tax assets after valuation allowance	$	—	$	—

Schedule of reconciliation of income tax expense (benefit) at the statutory federal income tax rate and income taxes

	Year Ended December 31,
	2018		2017		2016
Federal income tax expense at statutory rate	21.0	%	34.0	%	34.0	%
Permanent items	(0.9)		(0.6)		(1.2)
State income tax, net of federal benefit	0.1		2.8		7.5
R&D tax credits	4.3		1.1		5.2
Change in federal statutory rate on deferreds	(1.1)		(85.6)		—
Foreign income tax effect	(16.5)		(19.0)		—
Other	(1.6)		(1.1)		1.6
Change in valuation allowance	(5.3)		68.4		(47.1)
Effective income tax rate	0.0	%	0.0	%	0.0	%