13. SUBSEQUENT EVENTS	9 Months Ended
Jan. 31, 2018
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	Sale of Research and Development Assets On February 12, 2018, we sold the majority of our research and development assets to a third-party oncology therapeutics company (Note 10). Public Offering of Common Stock On February 14, 2018, we entered into an underwriting agreement (the “Underwriting Agreement”) with Wells Fargo Securities, LLC, as representative for the underwriters identified therein (collectively, the “Underwriters”), relating to the issuance and sale in an underwritten public offering of 9,000,000 shares of our common stock, par value $0.001 per share, at a public offering price of $2.25 per share (the “Offering”). In addition, pursuant to the Underwriting Agreement, we also granted the Underwriters a 30-day option to purchase up to an additional 1,350,000 shares of our Common Stock under this Offering at the public offering price of $2.25 per share less the underwriting discounts and commissions to cover over-allotments, if any (the “Overallotment Option”). On February 20, 2018, we completed the Offering pursuant to which we sold 10,294,445 shares of our Common Stock, including 1,294,445 shares sold pursuant to the Underwriter’s Overallotment Option at the public offering price of $2.25 per share. The aggregate gross proceeds we received from the Offering, including the shares sold pursuant to the Overallotment Option, was $23,163,000, before deducting underwriting discounts and commissions and other offering related expenses. We intend to use the net proceeds from the offering for the expansion of our contract manufacturing business and for general corporate purposes. The Offering was made pursuant to a prospectus supplement filed with the SEC on February 14, 2018 under our January 2018 Shelf (Note 6). As of March 12, 2018, aggregate gross proceeds of up to $101,837,000 remained available to us under the January 2018 Shelf. Series E Preferred Stock Dividend On March 7, 2018, our Board of Directors declared a quarterly cash dividend of $0.65625 per share on our Series E Preferred Stock. The dividend payment is equivalent to an annualized 10.50% per share, based on the $25.00 per share stated liquidation preference, accruing from January 1, 2018 through March 31, 2018. The cash dividend is payable on April 2, 2018 to holders of the Series E Preferred Stock of record on March 19, 2018.

13. SUBSEQUENT EVENTS

9 Months Ended

Jan. 31, 2018

Sale of Research and Development Assets

On February 12, 2018, we sold the majority of our research and development assets to a third-party oncology therapeutics company (Note 10).

Public Offering of Common Stock

On February 14, 2018, we entered into an underwriting agreement (the “Underwriting Agreement”) with Wells Fargo Securities, LLC, as representative for the underwriters identified therein (collectively, the “Underwriters”), relating to the issuance and sale in an underwritten public offering of 9,000,000 shares of our common stock, par value $0.001 per share, at a public offering price of $2.25 per share (the “Offering”). In addition, pursuant to the Underwriting Agreement, we also granted the Underwriters a 30-day option to purchase up to an additional 1,350,000 shares of our Common Stock under this Offering at the public offering price of $2.25 per share less the underwriting discounts and commissions to cover over-allotments, if any (the “Overallotment Option”).

On February 20, 2018, we completed the Offering pursuant to which we sold 10,294,445 shares of our Common Stock, including 1,294,445 shares sold pursuant to the Underwriter’s Overallotment Option at the public offering price of $2.25 per share. The aggregate gross proceeds we received from the Offering, including the shares sold pursuant to the Overallotment Option, was $23,163,000, before deducting underwriting discounts and commissions and other offering related expenses. We intend to use the net proceeds from the offering for the expansion of our contract manufacturing business and for general corporate purposes.

The Offering was made pursuant to a prospectus supplement filed with the SEC on February 14, 2018 under our January 2018 Shelf (Note 6). As of March 12, 2018, aggregate gross proceeds of up to $101,837,000 remained available to us under the January 2018 Shelf.

Series E Preferred Stock Dividend

On March 7, 2018, our Board of Directors declared a quarterly cash dividend of $0.65625 per share on our Series E Preferred Stock. The dividend payment is equivalent to an annualized 10.50% per share, based on the $25.00 per share stated liquidation preference, accruing from January 1, 2018 through March 31, 2018. The cash dividend is payable on April 2, 2018 to holders of the Series E Preferred Stock of record on March 19, 2018.