Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue
Grant revenue				$ 4,753,000
Type of Revenue [Extensible List]	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember
Operating expenses
Research and development	$ 5,070,000	$ 3,840,000	$ 11,085,000	$ 10,325,000
General and administrative	2,715,000	3,158,000	9,866,000	11,039,000
Loss on impairment of long-lived assets	2,914,000		5,784,000
Total operating expenses	10,699,000	6,998,000	26,735,000	21,364,000
Loss from operations	(10,699,000)	(6,998,000)	(26,735,000)	(16,611,000)
Interest income	8,000	232,000	251,000	811,000
Other income (expense), net	31,000	624,000	(13,000)	1,910,000
Net loss	$ (10,660,000)	$ (6,142,000)	$ (26,497,000)	$ (13,890,000)
Net loss per share - basic and diluted	$ (0.66)	$ (0.54)	$ (1.69)	$ (1.23)
Weighted-average common shares used to compute basic and diluted net loss per share	16,055	11,285	15,658	11,280