Property and Equipment (Details) - USD ($) $ in Thousands	Jul. 31, 2015	Apr. 30, 2015
Furniture and fixtures	$ 70	$ 70
Computer equipment and software	698	685
Laboratory equipment	510	493
Leasehold improvements	2	2
Total property and equipment	1,281	1,250
Less: Accumulated depreciation	(836)	(798)
Property and equipment, net	$ 445	$ 452