Condensed Consolidated Statements of Operations (Unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Grant		$ 0	$ 0	$ 3,888,000
Type of revenue [extensible list]	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember
Operating expenses:
Research and development	$ 17,839,000	$ 8,929,000	$ 47,034,000	$ 24,921,000
General and administrative	4,307,000	3,314,000	11,391,000	9,125,000
Total operating expenses	22,146,000	12,243,000	58,425,000	34,046,000
Loss from operations	(22,146,000)	(12,243,000)	(58,425,000)	(30,158,000)
Other income (expense):
Interest income	585,000	339,000	1,711,000	745,000
Other expense, net	(12,000)	(13,000)	(45,000)	(37,000)
Total other income	573,000	326,000	1,666,000	708,000
Net loss	$ (21,573,000)	$ (11,917,000)	$ (56,759,000)	$ (29,450,000)
Net loss per share, basic and diluted	$ (0.66)	$ (0.54)	$ (1.80)	$ (1.49)
Weighted-average common shares outstanding, basic and diluted	32,894,205	21,986,989	31,596,321	19,772,077