Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Revenue:
Total revenue	$ 1,022	$ 2,757
Operating expenses:
Research and development	24,083	23,000
General and administrative	6,026	3,874
Total operating expenses	30,109	26,874
Loss from operations	(29,087)	(24,117)
Other income (expense):
Interest and other income, net	357	420
Change in fair value of warrant liability		1,632
Share of loss from equity method investment	951	40
Net loss	(29,681)	(22,105)
Preferred dividends		(1,357)
Net loss available to common stockholders	$ (29,681)	$ (23,462)
Weighted-average common shares outstanding used in computing net loss per share available to common stockholders
Weighted-average common shares outstanding used in computing net loss per share available to common stockholders, basic and diluted:	8,458,277	3,146,632
Net loss per share available to common stockholders:
Net loss per share available to common stockholders, basic and diluted:	$ (3.51)	$ (7.45)
Collaboration revenue
Revenue:
Total revenue		$ 1,168
Grant revenue
Revenue:
Total revenue	$ 1,022	$ 1,589