Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Schedule of Reconciliation of the Statutory U.S. Federal Rate to the Company's Effective Tax Rate

A reconciliation of the statutory U.S. federal rate to the Company's effective tax rate is as follows:

	Years ended December 31,
	2020		2019		2018
Percent of pre-tax income:
U.S. federal statutory income tax rate	21.0	%	21.0	%	21.0	%
State taxes, net of federal benefit	14.8	%	10.9	%	18.5	%
Permanent items	0.2	%	(1.0)	%	4.0	%
Impact of state rate changes	0.1	%	0.1	%	(0.2)	%
Research and development credit	3.1	%	2.8	%	(2.4)	%
Change in valuation allowance	(34.8)	%	(33.6)	%	(42.6)	%
Effective income tax rate	4.4	%	0.2	%	(1.7)	%

Schedule of Components of Income Tax (Benefit) Expense

The components of income tax benefit are as follows:

	Years ended December 31,
	2020		2019		2018
Current:
Federal	$	—	$	—	$	—
State	(3,695)		(111)		(1,063)
Deferred:
Federal	—		—		—
State	—		—		—
Income tax benefit	$	(3,695)	$	(111)	$	(1,063)

Schedule of Significant Components of the Company's Deferred Tax Assets (Liabilities)

Significant components of the Company's deferred tax assets (liabilities) for 2020 and 2019 consist of the following:

	As of December 31,
	2020		2019
Deferred tax assets (liabilities)
License and technology payments	$	7,479	$	7,116
Share-based compensation	23,266		22,131
Accrued expenses	427		362
Right-of-use asset	(40)		(163)
Lease obligation	38		162
Depreciation	6		(18)
Federal and state net operating loss carryforwards	130,524		105,375
Research and development credits	9,959		7,353
Other	7		6
Deferred income tax assets	171,666		142,324
Valuation allowance	(171,666)		(142,324)
Net deferred tax assets	$	—	$	—

Schedule of Position With Respect to Uncertain Tax Positions

The Company's position with respect to uncertain tax positions is set forth below:

Opening balance	$	12,227
Gross amount of increases in unrecognized tax benefits during the period - current year provisions	—
Gross amount of increases in unrecognized tax benefits during the period - prior year provisions	—
Gross amount of decreases in unrecognized tax benefits during the period - other	(659)
Decreases due to settlement with tax authorities during the period	(4,845)
Reduction of unrecognized tax benefits due to expiration of the state of limitations during the period	—
Closing Balance	$	6,723