Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

Income Taxes

Schedule of provision for income taxes

The provision for annual income taxes consisted of the following (in thousands):

	As of December 31,
	2015		2014		2013
U.S. Federal	$	—	$	—	$	—
State		1		1		1
Foreign		11		6		16
Total current	$	12	$	7	$	17
Deferred:
U.S. Federal	$	(4)	$	—	$	—
State		—		—		—
Foreign		—		—		—
Total deferred	$	(4)	$	—	$	—
Total provision for income taxes	$	8	$	7	$	17

Reconciliation of federal statutory income tax

The reconciliation of federal statutory income tax to the Company's provision for income taxes is as follows (in thousands):

	As of December 31,
	2015		2014		2013
Expected provision at statutory federal rate	$	(7,134)	$	(7,741)	$	(3,080)
State tax—net of federal benefit		1		1		1
U.S. federal research credit		(924)		(1,125)		(2,272)
Non deductible expenses		119		104		28
Others		8		8		(9)
Change in valuation allowance		7,938		8,760		5,349
Provision for income taxes	$	8	$	7	$	17

Schedule of deferred tax assets and liabilities

Significant components of the Company's deferred tax assets and liabilities are as follows (in thousands):

	As of December 31,
	2015		2014
Deferred tax assets:
Net operating loss federal and state	$	30,836	$	22,442
Research and foreign tax credits		12,307		10,694
Accrued compensation and vacation		411		390
Deferred revenue, other accruals and reserves		3,918		3,077
Stock-based compensation		4,319		4,028
Patents		2,884		4,472
Gross deferred tax assets	$	54,675	$	45,103
Valuation allowance	$	(54,420)	$	(45,036)
Total deferred tax asset	$	255	$	67
Deferred tax liabilities:
Property and equipment	$	255	$	67
Total deferred tax liabilities	$	255	$	67
Net deferred tax assets	$	—	$	—

Schedule of unrecognized tax benefits roll forward

The following table summarizes the activity related to unrecognized tax benefits (in thousands):

	As of December 31,
	2015		2014		2013
Unrecognized benefit—beginning of period	$	3,261	$	2,656	$	1,840
Gross increase—prior period tax positions		—		—		274
Gross decreases—prior period tax positions		—		—		(90)
Gross increases—current period tax positions		496		605		632
Unrecognized benefit—end of period	$	3,757	$	3,261	$	2,656