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Background, Basis of Presentation and Liquidity (Details Narrative) - USD ($) $ / shares in Units, $ in Thousands						9 Months Ended		12 Months Ended
	Dec. 23, 2020	Nov. 20, 2020	Sep. 18, 2020	Oct. 24, 2019	Jan. 07, 2019	Jan. 31, 2021	Jan. 31, 2020	Apr. 30, 2020
Accumulated deficit						$ (229,696)		$ (220,136)
Net cash used in operating activities						(8,525)	$ (8,631)	10,500
Unrestricted cash and cash equivalents						$ 79,801		$ 10,002
2019 ATM Facility [Member] | Alliance Global Partners [Member]
Aggregate offering price					$ 25,000
Number of common stock shares sold					17,595,472
Proceeds from issuance or sale of equity, net of issuance costs					$ 23,400
Combined purchase price per share					$ 1.33
Payment of sales commission					$ 800
2020 ATM Facility [Member] | Alliance Global Partners [Member]
Aggregate offering price		$ 50,000
Number of common stock shares sold						17,179,883
Proceeds from issuance or sale of equity, net of issuance costs						$ 50,000
Combined purchase price per share						$ 2.91
Payment of sales commission						$ 1,600
Stock Purchase Agreement [Member] | Aspire Capital Fund, LLC [Member]
Number of common stock shares sold			6,424,205			2,250,000
Proceeds from issuance or sale of equity, net of issuance costs			$ 4,000			$ 7,400
Combined purchase price per share			$ 0.63			$ 3.28
Aggregate purchase of common stock			$ 12,500
Percentage of outstanding common stock limit for shareholder approval	19.99%		19.99%
Number of shares can be issued based upon outstanding percentage			3,722,251
Number of additional shares that can be issued upon shareholder approval	9,864,706
Stock Purchase Agreement [Member] | Aspire Capital Fund, LLC [Member] | Maximum [Member]
Aggregate purchase of common stock				$ 10,000

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