Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Collaboration revenue	$ 8,823
Operating expenses:
Research and development	59,042	$ 71,072
General and administrative	21,392	13,145
Total operating expenses	80,434	84,217
Loss from operations	(71,611)	(84,217)
Other income, net	792	1,540
Net loss	(70,819)	(82,677)
Cumulative convertible preferred stock dividends		(7,128)
Net loss attributable to common stockholders	$ (70,819)	$ (89,805)
Net loss per share attributable to common stockholders, basic and diluted	$ (2.79)	$ (8.13)
Weighted average number of common shares used in net loss per share attributable to common stockholders, basic and diluted	25,354	11,046
Comprehensive loss:
Net loss	$ (70,819)	$ (82,677)
Other comprehensive loss:
Unrealized loss on marketable securities	(2)
Total other comprehensive loss	(2)
Comprehensive loss	$ (70,821)	$ (82,677)