Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Components of Deferred Tax Assets

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

	December 31,
	2021			2020
Deferred tax assets:
Net operating loss carryforwards	$	99,450		$	88,013
Research and development credits		11,107			9,985
Depreciation and amortization		7,940			10,212
Accrued expenses		694			850
Lease liabilities		3,373			3,816
Stock compensation		4,083			3,856
Other, net		94			234
Total deferred tax assets		126,741			116,966
Less: valuation allowance		(124,040	)		(113,826	)
Total deferred tax assets, net of valuation allowance		2,701			3,140
Deferred tax liability:
Right-of-use assets		(2,701	)		(3,140	)
Total deferred tax liability		(2,701	)		(3,140	)
Total	$	—		$	—

Reconciliation of Expected Recovery of Income Taxes

The following is a reconciliation of the expected recovery of income taxes between those that are based on enacted tax rates and laws, to those currently reported for the years ended December 31 (in thousands):

	2021			2020			2019
Federal statutory rate	$	(10,748	)	$	(9,393	)	$	(9,382	)
State tax (net of federal benefit)		500			334			299
Permanent items, other		11			9			189
Stock compensation		1,349			1,595			2,470
Other adjustments		(204	)		687			523
Research and development credits		(1,870	)		(1,774	)		(1,595	)
Uncertain tax positions		748			710			638
Change in valuation allowance		10,214			7,832			6,858
Provision for income taxes	$	0		$	0		$	0

Unrecognized Tax Benefit

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

	December 31,
	2021			2020			2019
Balance at the beginning of the year	$	11,514		$	10,739		$	10,052
Adjustments related to prior year tax positions		(83	)		(21	)		(80	)
Increases related to current year tax positions		885			796			767
	$	12,316		$	11,514		$	10,739