Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Jan. 31, 2021	Apr. 30, 2020
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 9,193	$ 6,765
Less: Accumulated depreciation	(3,653)	(2,772)
Property and equipment, net	5,540	3,993
Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment	242	180
Computer Equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	1,888	1,209
Laboratory Equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	6,075	4,818
Asset In Progress
Property, Plant and Equipment [Line Items]
Total property and equipment	984	554
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 4	$ 4