KAL Callisto Pharmaceuticals,

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): April 7, 2008

Callisto Pharmaceuticals, Inc.

 (Exact name of registrant as specified in its charter)

420 Lexington Avenue, Suite 1609

New York, New York          10170

 (Address of principal executive offices)

Registrant’s telephone number, including area code: (212) 297-0010

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

o   Written communication pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o   Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o   Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o   Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 8.01.               Other Events.

Attached as Exhibit 99.1 and incorporated herein by reference, is a press release announcing the  filing by Callisto Pharmaceuticals, Inc. of an IND for SP-304 (Guanilib) in chronic constipation and irritable bowel syndrome.

Item 9.01               Financial Statements and Exhibits

(c)            Exhibits.

99.1                                                    Press Release of Callisto Pharmaceuticals, Inc. dated April 7, 2008.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Dated:    April 7, 2008

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