Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
License revenue	$ 38	$ 38	$ 114	$ 114
Research and development:
Noncash stock expense associated with in-licensing agreements				100
Noncash compensation	4,618	1,482	8,150	4,323
Other research and development	45,846	56,503	114,785	118,814
Total research and development	50,464	57,985	122,935	123,237
General and administrative:
Noncash compensation	23,712	593	38,618	1,391
Other general and administrative	11,584	2,321	25,373	6,580
Total general and administrative	35,296	2,914	63,991	7,971
Total costs and expenses	85,760	60,899	186,926	131,208
Operating loss	(85,722)	(60,861)	(186,812)	(131,094)
Other expense (income):
Interest expense	1,610	1,537	5,038	3,388
Other income	(169)	(468)	(687)	(1,183)
Total other expense, net	1,441	1,069	4,351	2,205
Net loss	$ (87,163)	$ (61,930)	$ (191,163)	$ (133,299)
Basic and diluted net loss per common share (in dollars per share)	$ (0.73)	$ (0.69)	$ (1.70)	$ (1.55)
Weighted average shares used in computing basic and diluted net loss per common share (in shares)	119,176,336	89,667,979	112,380,784	85,911,878