Summary of significant accounting policies - Schedule Of Estimated Lives of Property And Equipment (Detail)	12 Months Ended
	Sep. 30, 2020
Laboratory equipment
Property, Plant and Equipment, Useful Life	5 years
Furniture, fixtures and other equipment
Property, Plant and Equipment, Useful Life	5 years
Computer equipment
Property, Plant and Equipment, Useful Life	3 years
Computer software
Property, Plant and Equipment, Useful Life	3 years
Leasehold improvements
Property, Plant and Equipment, Estimated Useful Lives	Lesser of useful life or facilities’ lease term.