CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Grant revenue	$ 13,405	$ 3,966
Collaboration revenue	$ 4,742
Type of Revenue [Extensible List]	us-gaap:LicenseMember	us-gaap:LicenseMember
Total revenues	$ 18,147	$ 3,966
Operating expenses:
Research and development	65,775	33,885
General and administrative	15,588	12,887
Total operating expenses	81,363	46,772
Loss from operations	(63,216)	(42,806)
Other income (expense):
Gain on settlement of derivative liability	223
Interest income	1,328	1,101
Other income (expense), net	740	43
Total other income (expense), net	2,291	1,144
Net loss	$ (60,925)	$ (41,662)
Net loss per share attributable to common stockholders, basic and diluted	$ (3.35)	$ (2.60)
Weighted average common shares outstanding, basic and diluted:	18,160,525	16,001,832
Comprehensive loss:
Net loss	$ (60,925)	$ (41,662)
Other comprehensive gain (loss):
Unrealized gain (loss) on marketable securities	38	(28)
Reclassification adjustment for gains included in net loss	6
Net unrealized gains (losses) on securities	44	(28)
Total comprehensive loss	$ (60,881)	$ (41,690)