Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Reconciliation of the U.S. federal statutory income tax rate to effective income tax rate

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate for the years ended December 31, 2021, 2020, and 2019 were as follows:

	Year ended December 31,
	2021		2020		2019
Federal statutory rate	21.0	%	21.0	%	21.0	%
State taxes	16.3	%	(0.1)	%	(0.3)	%
Federal research tax credit	2.7	%	4.1	%	3.5	%
Stock compensation	(1.6)	%	(1.7)	%	(2.2)	%
Change in valuation allowance	(38.4)	%	(23.3)	%	(22.0)	%
	0.0	%	0.0	%	0.0	%

Summary of deferred income tax benefits and liabilities

Temporary differences and carryforwards that give rise to a significant portion of the deferred income tax benefits and liabilities were as follows at December 31, 2021 and 2020:

	December 31,
(dollars in millions)	2021		2020
Deferred income tax assets:
Loss carryforwards	$	97.0	$	43.1
Tax credits	18.8		10.1
Stock compensation	15.4		5.0
Deferred revenue	10.0		9.0
Other	3.3		0.1
Total deferred income tax assets	144.5		67.3
Deferred income tax liabilities:
Property, equipment and leasehold improvements	(3.6)		(2.4)
Other	(1.4)		—
Total deferred income tax liabilities	(5.0)		(2.4)
Less valuation allowance	(139.5)		(64.9)
Net deferred income tax liability	$	—	$	—