5. STOCKHOLDERS' EQUITY (Details Narrative) - USD ($)		12 Months Ended
		Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014	Jul. 14, 2016
Amounts remaining under registration statements					$ 112,445,000
Stock Incentive Plans [Member]
Common shares reserved for issuance		39,561,165
Employee Stock Purchase Plan [Member]
Common shares reserved for issuance		5,000,000
Warrants
Common shares reserved for issuance		273,280
Common Stock
Number of common stock shares issued, shares		42,372,195	13,665,117	33,527,369
Issuance costs		$ 677,000	$ 513,000	$ 1,504,000
Series E Preferred Stock [Member]
Issuance costs		$ 1,000	1,002,000	1,458,000
Common shares reserved for issuance	[1]	45,745,760
December 2012 AMI Agreement
Aggregate gross proceeds available in offering			75,000,000
Proceeds from sale of common stock, gross			75,000,000
Amounts remaining under registration statements			$ 0
June 2014 AMI Agreement | Common Stock
Aggregate gross proceeds available in offering		$ 25,000,000
Proceeds from sale of common stock, gross		25,000,000
Amounts remaining under registration statements		$ 0
June 2014 AMI Agreement | Series E Preferred Stock [Member]
Number of common stock shares issued, shares		2,676	799,764
Issuance costs		$ 1,000	$ 1,002,000
Amounts remaining under registration statements		10,735,000
Proceeds from sale of preferred stock, gross		60,000	$ 19,205,000
August 2015 AMI Sales Agreement [Member[
Aggregate gross proceeds available in offering		30,000,000
Amounts remaining under registration statements		22,553,000
Equity Distribution Agreement [Member]
Aggregate gross proceeds available in offering		20,000,000
Amounts remaining under registration statements		$ 13,031,000
Equity Distribution Agreement [Member] | Common Stock
Number of common stock shares issued, shares		8,472,288
Common Stock Purchase Agreement [Member]
Number of common stock shares issued, shares		18,518,518
Proceeds from sale of common stock, gross		$ 20,000,000
Issuance costs		$ 1,000
February 2014 Initial Public Offering [Member]
Issuance costs				1,458,000
Proceeds from sale of preferred stock, gross				$ 19,375,000
February 2014 Initial Public Offering [Member] | Series E Preferred Stock [Member]
Number of common stock shares issued, shares				775,000
Issuance costs				$ 1,458,000

[1] The Series E Preferred Stock is convertible into a number of shares of our common stock determined by dividing the liquidation preference of $25.00 per share by the conversion price, currently $3.00 per share. If all outstanding Series E Preferred Stock were converted at the $3.00 per share conversion price, the holders of Series E Preferred Stock would receive an aggregate of 13,145,333 shares of our common stock. However, we have reserved the maximum number of shares of our common stock that could be issued upon a change of control event assuming our shares of common stock are acquired for consideration of $0.855 per share or less. In this scenario, each outstanding share of Series E Preferred Stock could be converted into 29 shares of our common stock, representing the Share Cap.