Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Consolidated Statements of Operations
Revenue	$ 46.7	$ 21.8	$ 43.0
Operating expenses:
Research and development	180.4	108.4	67.2
General and administrative	61.6	38.3	27.3
Total operating expenses	242.0	146.7	94.5
Loss from operations	(195.3)	(124.9)	(51.5)
Other income (expense)
Other income, net	2.5	2.1	1.4
Interest income	1.9	3.6	4.6
Interest expense	(0.1)	(0.1)	(0.1)
Total other income	4.3	5.6	5.9
Loss from equity method investment	0.0	0.0	(24.7)
Net loss	$ (191.0)	$ (119.3)	$ (70.3)
Net loss per common share - basic (in usd per share)	$ (3.82)	$ (3.02)	$ (2.13)
Net loss per common share - diluted (in usd per share)	$ (3.82)	$ (3.02)	$ (2.13)
Weighted average common shares outstanding - basic (in shares)	50.0	39.5	32.9
Weighted average common shares outstanding - diluted (in shares)	50.0	39.5	32.9
Consolidated Statements of Comprehensive Loss
Net loss	$ (191.0)	$ (119.3)	$ (70.3)
Other comprehensive loss:
Unrealized (loss) gain on available-for-sale securities	(5.2)	0.5	0.3
Comprehensive loss	$ (196.2)	$ (118.8)	$ (70.0)