Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Total revenues	$ 3,669	$ 6,574
Operating expenses:
Research and development	44,330	48,788
General and administrative	18,952	12,674
Total operating expenses	63,282	61,462
Loss from operations	(59,613)	(54,888)
Other income	2,203	1,607
Net loss and comprehensive loss	$ (57,410)	$ (53,281)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (1.71)	$ (2.64)
Weighted-average number of common shares outstanding, basic and diluted (in shares)	33,556	20,199
Collaboration revenue
Revenues:
Total revenues	$ 3,669	$ 4,932
Grant revenue
Revenues:
Total revenues		$ 1,642