Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Schedule of Geographical Breakdown of Loss Before Provision for Income Taxes

The geographical breakdown of loss before provision for income taxes is as follows:

	Year Ended December 31,
	2021			2020			2019
	(in thousands)
United States	$	(95,605	)	$	(81,670	)	$	(89,459	)
International	$	943			910			1,024
Loss before provision for (benefit from) income    taxes, net	$	(94,662	)	$	(80,760	)	$	(88,435	)

Components of Provision (Benefit from) for Income Taxes

The components of the provision for (benefit from) income taxes are as follows:

	Year Ended December 31,
	2021			2020		2019
	(in thousands)
Current tax provision (benefit):
Federal	$	—		$	—	$	—
State		—			—		—
Foreign		38			59		85
Total current tax provision (benefit)	$	38		$	59	$	85
Deferred tax provision (benefit):
Foreign		(41	)		83		(245	)
Total deferred tax provision (benefit)	$	(41	)	$	83	$	(245	)
Total provision for (benefit from)    income taxes	$	(3	)	$	142	$	(160	)

Reconciliation Between Income Taxes Computed at the Federal Statutory Income Tax Rate and the Provision for Income Taxes

The reconciliation between income taxes computed at the federal statutory income tax rate and the provision for (benefit from) income taxes is as follows:

	Year Ended December 31,
	2021			2020			2019
Federal statutory rate		21.0	%		21.0	%		21.0	%
Effect of:
Change in valuation allowance		(27.8	)		(23.6	)		12.4
Federal tax credit		7.4			5.8			1.5
Warrant issuance and remeasurement		—			(4.2	)		(5.3	)
Effect of ownership change on deferred tax assets		(0.1	)		1.3			(29.0	)
State income tax benefit, net of federal benefit		—			0.2			0.2
Other permanent items		(0.5	)		(0.7	)		(0.6	)
Total provision for (benefit from) income    taxes%		0.0	%		(0.2	)%		0.2	%

Components of the Deferred Tax Assets

The components of the deferred tax assets are as follows:

	December 31,
	2021			2020
	(in thousands)
Deferred tax assets:
59 (e) expenditures and amortization	$	21,833		$	6,222
Net operating loss carryforwards		13,546			14,011
Federal R&D and orphan drug credits		11,992			5,107
Stock based compensation		8,806			6,459
License fee		4,691			3,224
Other		1,468			1,024
Gross deferred tax assets		62,336			36,047
Valuation allowance		(61,847	)		(35,513	)
Total deferred tax assets		489			534
Deferred tax liabilities:
Lease Asset		19			114
Other		82			73
Total deferred tax liabilities		101			187
Total net deferred tax assets	$	388		$	347

Unrecognized Tax Benefits

The activity related to the gross amount of unrecognized tax benefits is as follows:

	Year Ended December 31,
	2021			2020			2019
	(in thousands)
Beginning balance	$	621		$	314		$	264
Increases based on tax positions related to prior    years		39			—			—
Decreases based on tax positions related to prior    years		(83	)		(54	)		(103	)
Decreases due to ownership change		—			(207	)		—
Increases based on tax positions in current year		780			568			153
Settlement		—			—			—
Lapse of statute of limitations		—			—			—
Ending balance	$	1,357		$	621		$	314