4. PROPERTY AND EQUIPMENT (Details) - USD ($)	Oct. 31, 2016	Apr. 30, 2016
Property, Plant and Equipment [Abstract]
Leasehold improvements	$ 19,990,000	$ 19,610,000
Laboratory equipment	10,569,000	10,257,000
Furniture, fixtures, office equipment and software	4,227,000	4,045,000
Total property and equipment	34,786,000	33,912,000
Less accumulated depreciation and amortization	(10,829,000)	(9,610,000)
Total property and equipment, net	$ 23,957,000	$ 24,302,000