Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue:
Collaboration revenue - related party	$ 5,462,000	$ 6,615,000
Type of Revenue [Extensible List]	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember
Grant revenue	$ 739,000	$ 446,000
Collaboration revenue	1,988,000	260,000
Total revenue	8,189,000	7,321,000
Operating expenses:
Research and development expenses	21,743,000	22,887,000
General and administrative expenses	6,138,000	7,495,000
Restructuring expenses	0	1,492,000
Total operating expenses	27,881,000	31,874,000
Loss from operations	(19,692,000)	(24,553,000)
Other income (expense):
Interest income	159,000	220,000
Interest expense	(716,000)
Other income	368,000
Total other income (expense), net	(189,000)	220,000
Net loss	$ (19,881,000)	$ (24,333,000)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.28)	$ (0.59)
Weighted average common shares outstanding, basic and diluted	70,821,514	41,027,824
Net loss	$ (19,881,000)	$ (24,333,000)
Other comprehensive loss:
Unrealized loss on investments, net of tax of $0	(10,000)
Total other comprehensive loss	(10,000)
Comprehensive loss	$ (19,891,000)	$ (24,333,000)