Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Consolidated Statements of Operations [Abstract]
Revenue	$ 0	$ 0	$ 0	$ 0
Operating expenses:
Research and development	24,798	16,731	53,340	33,687
General and administrative	9,250	6,828	19,930	13,990
Total operating expenses	34,048	23,559	73,270	47,677
Loss from operations	(34,048)	(23,559)	(73,270)	(47,677)
Research and development incentives	0	0	500	0
Interest expense	(251)	(1,786)	(1,980)	(3,360)
Interest and other income - net	501	429	1,412	1,395
Amortization of premium on investments - net	(727)	(124)	(1,366)	(62)
Net loss	$ (34,525)	$ (25,040)	$ (74,704)	$ (49,704)
Net loss per share attributable to common stockholders - basic (in dollars per share)	$ (0.55)	$ (0.45)	$ (1.20)	$ (0.90)
Net loss per share attributable to common stockholders - diluted (in dollars per share)	$ (0.55)	$ (0.45)	$ (1.20)	$ (0.90)
Weighted-average common shares outstanding - basic (in shares)	63,061,232	55,158,459	62,321,926	55,020,789
Weighted-average common shares outstanding - diluted (in shares)	63,061,232	55,158,459	62,321,926	55,020,789