Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

Income Taxes

Schedule of tax effects of temporary differences that give rise to significant portions of deferred tax assets

	December 31
	2015			2014
Deferred tax assets:
Net operating loss carryforwards	$	54,197		$	46,853
Research credit carryforward		4,527			3,683
Stock options and other		1,474			795
Total gross deferred tax assets		60,198			51,331
Valuation allowance for deferred tax assets		(60,198	)		(51,331	)
Net deferred tax assets	$	—		$	—

Schedule of reconciliation of U.S. statutory income tax rate to effective tax rate

	December 31,
	2015			2014			2013
Federal income tax at statutory rate		34.0	%		34.0	%		34.0	%
State income tax benefit, net of federal benefit		6.0	%		6.0	%		5.7	%
Research and development tax credits		2.0	%		3.0	%		2.7	%
Other		(2.0	)%		—	%		(1.4	)%
Increase to valuation allowance		(24.0	)%		(24.0	)%		(41.0	)%
Effective income tax rate		16.0	%		19.0	%		0.0	%