Condensed Consolidated Statements of Operations (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues:
Grant	$ 0	$ 1,510,000
Type of revenue [extensible list]	us-gaap:GrantMember	us-gaap:GrantMember
Operating expenses:
Research and development	$ 14,389,000	$ 6,870,000
General and administrative	3,268,000	2,885,000
Total operating expenses	17,657,000	9,755,000
Loss from operations	(17,657,000)	(8,245,000)
Other income (expense):
Interest income	507,000	143,000
Other expense, net	(17,000)	(17,000)
Total other income	490,000	126,000
Net loss	$ (17,167,000)	$ (8,119,000)
Net loss per share, basic and diluted	$ (0.59)	$ (0.49)
Weighted-average common shares outstanding, basic and diluted	29,011,737	16,672,125