CONDENSED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Revenue	$ 0	$ 320
Operating expenses:
Research and development	22,320	11,449
General and administrative	3,327	3,159
Total operating expenses	25,647	14,608
Loss from operations	(25,647)	(14,288)
Other income (expense):
Loss from remeasurement of development derivative liability	(1,426)	(454)
Interest income	2	211
Interest expense	(285)	(378)
Foreign exchange (loss) gain	(2)	4
Total other expense	(1,711)	(617)
Net loss	$ (27,358)	$ (14,905)
Net loss per common share, basic and diluted (in usd per share)	$ (0.87)	$ (0.52)
Weighted average common shares outstanding, basic, and diluted (in shares)	31,282,662	28,773,274
Revenue from Contract with Customer, Product and Service [Extensible List]		us-gaap:GrantMember