Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Reconciliation of Total Income Tax Provision

A reconciliation of the total income tax provision tax rate to the statutory federal income tax rates of 21% for the years ended December 31, 2021 and 2020, respectively, is as follows:

	2021			2020
Income tax expense (benefit) at federal statutory rate		(21.0	)%		(21.0	)%
Change in valuation allowance		0.9	%		23.6	%
Income tax expense (benefit) at state statutory rate		(0.6	)%		(8.9	)%
Stock compensation		0.7	%		6.9	%
NOLs expiring and adjustments to NOL		20.3	%		6.0	%
Research credit		(0.8	)%		(1.1	)%
Return to provision		0.5	%		1.0	%
Change in state rate		—			(0.5	)%
Mark to market adjustment		—			(6.1	)%
Other, net		—			0.1	%
		0.0	%		0.0	%

Deferred Tax Assets and Liabilities

The tax effects of temporary differences that give rise to significant portions of our deferred tax assets and deferred tax liabilities as of December 31, 2021 and 2020 are as follows (in thousands):

	2021			2020
Deferred tax assets:
Accrued expenses	$	41		$	128
Stock based compensation		164			168
Net operating loss carryforwards		95,310			95,114
Income tax credit carryforwards		8,864			8,756
Property and equipment, principally due to differences in depreciation		19			16
Intangible assets		451			556
Other, net		82			182
		104,931			104,920
Valuation allowance		(104,857	)		(104,742	)
Total deferred tax assets, net of allowance		74			178
Deferred tax liabilities:
Other		(74	)		(178	)
Total deferred tax liability		(74	)		(178	)
Net deferred tax assets (liability)	$	—		$	—

Unrecognized Tax Benefits Activity

Following is a tabular reconciliation of the unrecognized tax benefits activity during the years ended December 31, 2021 and 2020 (in thousands):

	2021			2020
Unrecognized Tax Benefits – Beginning	$	2,223		$	2,234
Gross decreases – tax positions in prior period		(44	)		(44	)
Gross increase – current-period tax positions		69			33
Unrecognized Tax Benefits – Ending	$	2,248		$	2,223