Condensed Consolidated Statements of Operations (Unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues:
Grant	$ 0	$ 1,261,000	$ 3,888,000	$ 3,723,000
Type of revenue [extensible list]	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember
Operating expenses:
Research and development	$ 8,929,000	$ 6,239,000	$ 24,921,000	$ 17,024,000
General and administrative	3,314,000	3,020,000	9,125,000	7,749,000
Total operating expenses	12,243,000	9,259,000	34,046,000	24,773,000
Loss from operations	(12,243,000)	(7,998,000)	(30,158,000)	(21,050,000)
Other income (expense):
Interest income	339,000	136,000	745,000	332,000
Other expense, net	(13,000)	(12,000)	(37,000)	(35,000)
Total other income	326,000	124,000	708,000	297,000
Net loss	$ (11,917,000)	$ (7,874,000)	$ (29,450,000)	$ (20,753,000)
Net loss per share, basic and diluted	$ (0.54)	$ (0.48)	$ (1.49)	$ (1.42)
Weighted-average common shares outstanding, basic and diluted	21,986,989	16,409,871	19,772,077	14,641,082