4. PROPERTY AND EQUIPMENT (Details) - USD ($)	Jan. 31, 2018	Apr. 30, 2017
Property, Plant and Equipment [Abstract]
Leasehold improvements	$ 20,579,000	$ 20,098,000
Laboratory equipment	10,683,000	10,777,000
Furniture, fixtures, office equipment and software	4,688,000	4,499,000
Construction-in-progress	2,558,000	2,841,000
Total property and equipment	38,508,000	38,215,000
Less accumulated depreciation and amortization	(12,183,000)	(11,700,000)
Total property and equipment, net	$ 26,325,000	$ 26,515,000