Callisto Pharmaceuticals to Host Conference Call: An Update on L-Annamycin and Q&A With Dr. Hagop Kantarjian, Chairman, Leukemia Department, The University of Texas M.D. Anderson Cancer Center

Thursday, February 3rd, at 4:30 pm Eastern Time

Callisto Pharmaceuticals, Inc. , a biopharmaceutical company primarily focused on the development of drugs to treat cancer and osteolytic bone disease, announced today it will hold a conference call and simultaneous webcast on Thursday, February 3, 2005 to provide an update on L-Annamycin. The call will be followed by a question and answer session, hosted by Dr. Hagop Kantarjian, Principal Investigator for Callisto's proposed Phase IIb trial in adult relapsed acute lymphoblastic leukemia. The call will begin at 4:30 pm Eastern Time.

To participate on the conference call, please dial (617) 847-8712 at least 15 minutes before the start of the call. When prompted for a passcode, please enter 30501394. An audio web cast of the call will be accessible at www.callistopharma.com. Those who wish to listen to the conference call on the Internet should visit the Investor Relations section of the website at least 15 minutes before the event's broadcast. Instructions will be provided to ensure that the necessary audio applications are able to be downloaded if necessary. All programs can be downloaded at no charge to the user.

A replay of the call will be available two hours after the completion of the call at (888) 286-8010, passcode 13388924. The replay will be accessible through Thursday, February 10th.

About Callisto Pharmaceuticals, Inc.

Callisto is a biopharmaceutical company focused on the development of drugs to treat cancer and osteolytic bone disease. Callisto recently in-licensed Annamycin, a drug to treat leukemia, based on the drug's novel therapeutic profile, including activity against resistant diseases and significantly reduced toxicity. Callisto intends to initiate a Phase IIb clinical trial of Annamycin in relapsed acute lymphocytic leukemia patients in the first half of 2005. Callisto's second drug, Atiprimod, is in a Phase I/IIa clinical trial in relapsed multiple myeloma patients, and is a small-molecule, orally available drug with antiproliferative and antiangiogenic activity. Callisto also has drugs in preclinical development for melanoma, gastrointestinal inflammation, and a program focused on the development of a drug to protect against staphylococcus and streptococcus biowarfare agents. Callisto has exclusive worldwide licenses from AnorMED Inc. and M.D. Anderson Cancer Center to develop, manufacture, use and sell Atiprimod and Annamycin, respectively. For additional information, visit www.callistopharma.com.

Forward-Looking Statements

Certain statements made in this press release are forward-looking. Such statements are indicated by words such as "expect," "should," "anticipate" and similar words indicating uncertainty in facts and figures. Although Callisto believes that the expectations reflected in such forward-looking statements are reasonable, it can give no assurance that such expectations reflected in such forward-looking statements will prove to be correct. As discussed in the Callisto Pharmaceuticals Annual Report on Form 10-KSB for the year ended December 31, 2003,and other periodic reports, as filed with the Securities and Exchange Commission, actual results could differ materially from those projected in the forward-looking statements as a result of the following factors, among others: uncertainties associated with product development, the risk that products that appeared promising in early clinical trials do not demonstrate efficacy in larger-scale clinical trials, the risk that Callisto will not obtain approval to market its products, the risks associated with dependence upon key personnel and the need for additional financing.

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