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Background, Basis of Presentation and Liquidity (Details Narrative) - USD ($)				3 Months Ended
	Oct. 24, 2019	Apr. 08, 2019	Jan. 07, 2019	Jul. 31, 2020	Jul. 31, 2019	Apr. 30, 2020
Accumulated deficit				$ (223,521,000)		$ (220,136,000)
Cash, cash equivalents and restricted cash, at carrying value				11,993,000		$ 10,930,000
Revenues				$ 200,000	$ 200,000
Aggregate offering price		$ 15,700,000
Number of common stock shares sold		1,542,000
Pre-funded Warrants [Member]
Warrant to purchase shares common stock		3,385,680
Over-Allotment Option [Member]
Number of common stock shares sold		642,000
2019 ATM Facility [Member] | A.G.P./ Alliance Global Partners [Member]
Aggregate offering price			$ 25,000,000
Number of common stock shares sold				5,913,362
Proceeds from issuance or sale of equity, net of issuance costs				$ 5,000,000
Combined purchase price per share				$ 0.85
Payment of sales commission				$ 162,448
Securities Purchase Agreement [Member]
Warrant to purchase shares common stock		4,927,680
Stock Purchase Agreement [Member] | Aspire Capital Fund, LLC [Member]
Number of common stock shares sold				6,424,205
Proceeds from issuance or sale of equity, net of issuance costs				$ 4,000,000
Combined purchase price per share				$ 0.63
Aggregate purchase of common stock	$ 10,000,000
Percentage of outstanding common stock limit for shareholder approval	19.99%
Stock Purchase Agreement [Member] | Aspire Capital Fund, LLC [Member] | December 20, 2019 [Member]
Stock issued for new issue, shares	5,400,000
Stock Purchase Agreement [Member] | Aspire Capital Fund, LLC [Member] | Maximum [Member]
Percentage of outstanding common stock limit for shareholder approval	19.99%
Number of shares can be issued based upon outstanding percentage	1,219,010
Common stock issued for commitment fee	194,805

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