Income Taxes (Tables)

12 Months Ended

Dec. 31, 2015

Loss before Income Tax Attributable to Geographic Location

Loss before income taxes is attributed to the following geographic locations for the years ended December 31,


	2015		2014
United States	$	36,065,000	$	30,215,000
Foreign		350,000		2,526,000

Total loss before income taxes	$	36,415,000	$	32,741,000

Components of Deferred Tax Assets and Liabilities

Significant components of our deferred tax assets and liabilities at December 31 are as follows:


	2015			2014
Deferred tax assets:
Capitalized research and development costs	$	75,409,000		$	66,212,000
Net operating losses		59,319,000			57,261,000
Research and development credits		10,581,000			9,798,000
Stock-based compensation		1,925,000			1,124,000
Capital loss carryover		264,000			254,000
Fixed assets		(107,000	)		393,000
Other		4,707,000			3,930,000

		152,098,000			138,972,000
Valuation allowance		(152,098,000	)		(138,972,000	)

Total deferred tax assets	$	—		$	—

Reconciliation of Federal Income Tax Rate

The effective tax rate as a percentage of income before income taxes differs from the statutory federal income tax rate (when applied to income before income taxes) for the years ended December 31 as follows:


	2015			2014			2013
Statutory federal income tax (benefit) rate		(34	)%		(34	)%		(34	)%
State income tax (benefit) rate		(0.6	)		—			—
Increase resulting from:
Expenses not deductible for taxes		0.1			0.8			0.5
Increase in valuation allowance		36.0			32.6			38.8
Change in state deferred tax rate		(2.2	)		0.0			1.1
Change in foreign deferred tax rate		0.3			2.8			0.9
Expiration of tax attributes		1.2			1.7			0.5
Prior year true up		2.5			1.1			(0.7	)
Tax credits		(2.5	)		(2.4	)		(3.0	)
Warrant valuation		(0.9	)		(2.5	)		(4.1	)

Effective tax (benefit) rate		0	%		0	%		0	%