Callisto Pharmaceuticals Announces Additional Clinical Trial Sites for Atiprimod

Company's Cancer Drug Now Under Clinical Trial at Four Leading Cancer Research Institutions

Callisto Pharmaceuticals, Inc. , a biopharmaceutical company primarily focused on the development of drugs to treat cancer and osteolytic bone disease, announced today the opening of two additional sites for the Phase I/IIa clinical trial of Atiprimod. The new sites include the Roswell Park Cancer Institute in Buffalo, New York and the St. Vincent's Comprehensive Cancer Center in New York, NY. Atiprimod is Callisto's lead drug candidate for treatment of multiple myeloma (MM). The trial is presently underway at two leading cancer centers in the United States, the Dana-Farber Cancer Institute in Boston, Massachusetts, and The University of Texas M. D. Anderson Cancer Center, Houston, Texas.

"We are pleased to announce the addition of these two sites at Roswell Park and St. Vincent Hospital to our Atiprimod clinical trial," said Callisto Executive VP, R&D Dr. Donald Picker. "The new sites, both of which are leading institutions for the study of cancer and bone disease, will provide additional patients for the ongoing trial."

The primary objective of the Phase I/IIa trial is to provide additional data for the identification of the maximum tolerated dose of Atiprimod in patients. The secondary objectives are to provide additional data on 1) the measurement of its pharmacokinetics, 2) the response to Atiprimod in patients with relapsed multiple myeloma, and 3) the screening of surrogate markers to explore any potential drug effect in multiple myeloma patients.

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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