Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Oct. 31, 2018	Apr. 30, 2018
Property, Plant and Equipment [Abstract]
Furniture and fixtures	$ 74	$ 73
Computer equipment and software	1,020	973
Laboratory equipment	3,153	2,490
Assets in progress	25	15
Total property and equipment	4,272	3,551
Less: Accumulated depreciation	(1,737)	(1,468)
Property and equipment, net	$ 2,535	$ 2,083

Assets in Progress, Gross

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Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated amortization of capitalized costs for computer software, including but not limited to, acquired and internally developed computer software.

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Amount before accumulated depreciation of equipment commonly used in offices and stores that have no permanent connection to the structure of a building or utilities. Examples include, but are not limited to, desks, chairs, tables, and bookcases.

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Amount before accumulated depreciation of tangible personal property used to produce goods and services, including, but is not limited to, tools, dies and molds, computer and office equipment.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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