Income taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income taxes

Schedule of significant components of deferred income tax assets and liabilities

	December 31,
	2018		2017
	(in thousands)
Deferred Tax Assets:
Net operating loss	$	37,818	$	32,193
Share-based compensation		1,757		1,340
R&D tax credit		2,378		1,696
Other reserves		1,616		1,069
Capital lease liability		390		563
State deferreds		1,236		397
Inventory		103		829
Accrued rebates		4,902		561
Other current assets		—		319
Other		2,456		2,597
Total deferred tax assets		52,656		41,564
Deferred Tax Liabilities:
Intangible assets		(1,571)		(1,846)
Property and equipment		(999)		(747)
Total deferred tax liabilities		(2,570)		(2,593)
Valuation allowance		(50,086)		(38,971)
Net deferred tax asset (liability)	$	—	$	—

Schedule of gross unrecognized tax benefits

	December 31,
	2018		2017
		(in thousands)
Beginning Balance	$	7,261	$	5,081
Decrease based on tax positions taken during a current period		(3,305)		2,180
Ending Balance	$	3,956	$	7,261

Schedule of reconciliation of Federal statutory tax rate

	Year Ended
	December 31,
	2018		2017
U.S. Statutory Tax Rate	21	%	34	%
Change in Valuation Allowance	(21.5)	%	44	%
Deferred Tax Adjustments	0	%	(47)	%
Federal Rate Change	0	%	(31)	%
State tax expense, net	1.8	%	2	%
Provision to Return and Other Adjustments	(1.3)	%	(2)	%
Tax Expense / (Benefit)	0	%	0	%