Summary of Significant Accounting Policies - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Apr. 30, 2016	Apr. 30, 2015
Accounting Policies [Abstract]
Furniture and fixtures	$ 73	$ 70
Computer equipment and software	715	685
Laboratory equipment	782	493
Leasehold improvements	2	2
Total property and equipment	1,572	1,250
Less: Accumulated depreciation and amortization	(954)	(798)
Property and equipment, net	$ 618	$ 452

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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 additions or improvements to assets held under a lease arrangement.

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