Callisto Pharmaceuticals Reports Preclinical Data on Anticancer and Antiangiogenic Activities of Atiprimod

Callisto Pharmaceuticals, Inc. , a biopharmaceutical company primarily focused on the development of drugs to treat cancer and osteolytic bone disease, today announced that an article entitled "Atiprimod Is An Inhibitor Of Cancer Cell Proliferation And Angiogenesis" will be published in the Journal of Experimental Therapeutics and Oncology (volume 4, pages 267-279, December 27, 2004). This journal is devoted to the rapid publication of innovative preclinical investigations on therapeutic agents against cancer, and pertinent findings of experimental and clinical oncology.

Atiprimod is Callisto's lead drug candidate for treatment of multiple myeloma and is currently undergoing a Phase I/IIa clinical trial in patients with relapsed multiple myeloma. The trial is 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 in Houston Texas.

The publication, jointly authored by scientists from Callisto and the National Cancer Institute (NCI), reports preclinical data suggesting anti-cancer and antiangiogenic activities of Atiprimod. According to Dr. Shailubhai, the lead author of the article, Atiprimod has unique properties centering on its ability to inhibit angiogenesis and proliferation of a wide range of human cancer cells, as well as its ability to inhibit production of two essential factors for tumor growth and metastasis: vascular endothelial growth factor (VEGF) and Interleukin-6 (IL-6).

The article also notes that Atiprimod is more effective in inhibiting proliferation of metastatic cells as compared to the non-metastatic cells from the same tumor type. "We are excited about these data, and look forward to the clinical results from the Atiprimod trial in relapsed multiple myeloma patients." commented Dr. Shailubhai.

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.