Property and Equipment - Components of Property and Equipment (Detail) - USD ($) $ in Thousands	Apr. 30, 2022	Apr. 30, 2021
Property, Plant and Equipment [Line Items]
Total property and equipment at cost	$ 4,597	$ 3,880
Less: Accumulated depreciation	(2,419)	(2,089)
Property and equipment, net	2,178	1,791
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment at cost	2,153	1,748
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment at cost	148	45
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment at cost	299	215
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment at cost	$ 1,997	$ 1,872