Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Revenue from collaboration agreements	$ 33,195	$ 21,381
Operating expenses:
Research and development	78,440	48,059
General and administrative	15,204	8,774
Total operating expenses	93,644	56,833
Operating loss	(60,449)	(35,452)
Other (expense) income
Change in fair value of warrant liability—related party	(5,676)
Interest expense and amortization of long-term debt—related party	(1,229)
Interest and other income, net	393	2,157
Total other (expense) income	(6,512)	2,157
Loss before income taxes	(66,961)	(33,295)
Income tax benefit (expense)	626	(804)
Net loss	(66,335)	(34,099)
Unrealized gain on marketable securities	13
Comprehensive loss	(66,322)	(34,099)
Reconciliation of net loss to net loss attributable to common stockholders:
Net loss	(66,335)	(34,099)
Accrual of preferred stock dividends		(8,468)
Net loss attributable to common stockholders—basic and diluted	$ (66,335)	$ (42,567)
Net loss per share attributable to common stockholders—basic and diluted	$ (5.83)	$ (31.03)
Weighted-average common stock outstanding—basic and diluted	11,370,328	1,371,905