Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Taxes [Abstract]

Components of Provision for Income Taxes

The components of our provision for income taxes are as follows for the periods indicated:

		Year Ended
		December 31,
(in thousands)		2023		2022
Current
Federal and state	$	—	$	—
Foreign		147		109
Total provision for income taxes	$	147	$	109

Reconciliation of Taxes at the Federal Statutory Rate

	Year Ended
	December 31,
	2023		2022
Tax at federal statutory rate	21.0	%	21.0	%
Permanent differences	(4.3)		(2.1)
Research and development ("R&D") tax credit	1.4		0.8
Uncertain tax position	(0.3)		(0.3)
State, net of federal benefit	2.6		(0.5)
Deferred rate change	0.4		0.3
Change in valuation allowance	(21.2)		(19.5)
Total	(0.4)	%	(0.3)	%

Components of Net Deferred Tax Assets

		Year Ended
		December 31,
(in thousands)		2023		2022
Deferred tax assets
Net operating loss carryforwards	$	89,173	$	82,050
R&D tax credits		9,664		9,072
Capitalized R&D expenses		8,963		8,412
Non-qualified stock options		1,473		752
Start-up costs		680		894
Accrued vacation		179		212
Property and equipment		59		144
Other		361		300
Total deferred tax assets		110,552		101,836
Valuation allowance		(110,552)		(101,836)
Net deferred tax assets	$	—	$	—

Changes to Gross Unrecognized Tax Benefits

The changes to our gross unrecognized tax benefits were as follows for the periods indicated:

		Year Ended
		December 31,
(in thousands)		2023		2022
Gross unrecognized tax benefits at beginning of year	$	2,046	$	1,939
Gross increases:
Prior year tax positions		12		4
Current year tax positions		185		113
Gross decreases:
Prior year tax positions		(22)		(10)
Gross unrecognized tax benefits at end of year	$	2,221	$	2,046