Quarterly Financial Data (unaudited) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Data
Revenue					$ 86,000					$ 86,000
Revenue, Product and Service [Extensible List]					us-gaap:GrantMember					us-gaap:GrantMember
Operating expenses:
Research and development	$ 7,457,953	$ (1,604,399)	$ 8,223,783	$ 6,306,712	$ 4,876,162	$ 4,859,902	$ 8,533,466	$ 8,975,513
General and administrative	3,958,211	3,530,617	3,287,276	3,159,657	3,256,044	3,125,780	3,436,340	3,420,623	$ 13,935,761	$ 13,238,787	$ 10,016,902
Total operating expenses	11,416,164	1,926,218	11,511,059	9,466,369	8,132,206	7,985,682	11,969,806	12,396,136	34,319,810	40,483,830	32,823,009
Loss from operations	(11,416,164)	(1,926,218)	(11,511,059)	(9,466,369)	(8,046,206)	(7,985,682)	(11,969,806)	(12,396,136)	(34,319,810)	(40,397,830)	(32,823,009)
Other income (expense):
Interest income	295,140	436,846	439,201	350,951	321,621	278,214	186,304	175,184	1,522,138	961,323	519,554
Foreign exchange loss	406,033	(457,018)	(63,327)	(31,599)	(65,658)	(99,897)	(223,731)	(85,382)	(145,911)	(474,668)	291,151
Total other income	701,173	(20,172)	375,874	319,352	255,963	178,317	(37,427)	89,802	1,376,227	486,655	810,705
Net loss	$ (10,714,991)	$ (1,946,390)	$ (11,135,185)	$ (9,147,017)	$ (7,790,243)	$ (7,807,365)	$ (12,007,233)	$ (12,306,334)	$ (32,943,583)	$ (39,911,175)	$ (32,012,304)
Net loss per share basic and diluted	$ (0.46)	$ (0.08)	$ (0.50)	$ (0.47)	$ (0.44)	$ (0.47)	$ (0.89)	$ (0.91)	$ (1.50)	$ (2.61)	$ (2.48)
Basic and diluted weighted average shares outstanding	23,191,428	23,186,410	22,116,758	19,452,088	17,616,373	16,587,353	13,504,485	13,467,694	22,000,203	15,308,886	12,914,814
Australian Taxation Office
Research and development
Research and development incentive and tax receivable	$ 8,300,000	$ 8,300,000							$ 8,300,000
Research and development incentive tax credit		$ 8,300,000							$ 8,300,000