Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense (Benefit)

The components of income before taxes are as follows (in thousands):

	Year Ended December 31,
	2020		2019		2018
United States	$	(47,365)	$	(52,415)	$	(37,630)
International	—		—		—
	$	(47,365)	$	(52,415)	$	(37,630)

Schedule of Effective Income Tax Rate Reconciliation

A reconciliation of the statutory U.S. federal rate to the Company’s effective tax rate is as follows (in thousands):

	Year Ended December 31,
	2020		2019		2018
Tax at federal statutory rate	$	(9,947)	$	(11,007)	$	(7,902)
State taxes, net of federal benefit	(1,958)		(2,270)		(1,582)
Permanent differences	(8,489)		(4,731)		289
Loss on Series C warrant liability	—		5,330		2,500
Change in valuation allowance	22,164		12,797		6,197
General business credits	(1,268)		(319)		136
Other	(491)		208		376
Provision for income taxes	$	11	$	8	$	14

Schedule of Deferred Tax Assets and Liabilities

Significant components of the Company’s net deferred tax assets as of December 31, 2020 and 2019 consist of the following (in thousands):

	December 31,
	2020		2019
Deferred tax assets:
Net operating loss carryforwards	$	63,069	$	44,574
Research and development credits	7,191		5,287
Capitalized start-up costs/Intangibles	8		11
Accruals and reserves	2,337		2,227
Property and equipment	—		188
Stock-based compensation	1,859		568
Operating lease liability	935		1,133
Interest limitation	813		—
Total deferred tax assets	76,212		53,988
Less: Valuation allowance	(75,289)		(53,126)
Deferred tax liabilities:
Operating lease asset	(707)		(862)
Property and equipment	(216)		—
Total deferred tax liabilities	(923)		(862)
Net deferred tax assets	$	—	$	—

Reconciliation of Unrecognized Tax Benefits

A reconciliation of the unrecognized tax benefits from January 1, 2018 to December 31, 2020 is as follows (in thousands):

	December 31,
	2020		2019		2018
Balance at the beginning of year	$	1,436	$	1,348	$	615
Increases related to current years’ tax positions	342		88		118
Increases related to prior years’ tax positions	241		—		615
Balance at end of year	$	2,019	$	1,436	$	1,348