Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) (unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
License revenue	$ 0		$ 15,000,000
Revenue, Product and Service [Extensible List]	arpo:LicenseRevenueMember		arpo:LicenseRevenueMember
Operating expenses
Research and development	$ 3,985,988	$ 2,844,603	$ 9,363,602	$ 10,695,109
General and administrative	1,875,415	2,160,845	6,356,821	8,215,456
Restructuring (benefit) expense		(38,810)		876,284
Total operating expenses	5,861,403	4,966,638	15,720,423	19,786,849
Loss from operations	(5,861,403)	(4,966,638)	(720,423)	(19,786,849)
Grant income		79,303	79,900	99,574
Other income	897,378		897,378
Interest income	9,002	239,405	145,491	862,904
Total other income	906,380	318,708	1,122,769	962,478
Net and comprehensive (loss) income	$ (4,955,023)	$ (4,647,930)	$ 402,346	$ (18,824,371)
Net and comprehensive (loss) income per share
Basic and diluted	$ (0.12)	$ (0.11)	$ 0.01	$ (0.46)
Weighted average number of common shares used in computing net and comprehensive (loss) income per share basic and diluted
Basic	42,139,493	40,588,004	41,108,942	40,588,004
Diluted	42,139,493	40,588,004	41,477,388	40,588,004