Callisto Pharmaceuticals, Inc. (OTCBB:CLSP) today announced that researchers at Dana-Farber Cancer Institute (Boston) and The University of Texas M. D. Anderson Cancer Center (Houston) presented preclinical data on Atiprimod, Callisto Pharmaceuticals’ lead drug candidate for multiple myeloma, at oral and poster presentations given at the 45th Annual Meeting of the American Society of Hematology, held in San Diego, Calif., December 6-9, 2003.

Dr. Zeev Estrov and his colleagues at M. D. Anderson, in a talk entitled “Atiprimod Inhibits Proliferation, Blocks STAT3 Phosphorylation, Causes Cell Cycle Arrest and Induces Apoptosis in Multiple Myeloma (MM) Cells,” described experiments performed on human multiple myeloma cells that begin to define the underlying mechanism-of-action of Atiprimod’s anticancer activity in culture. Atiprimod is shown to affect the activation of a key signaling enzyme in multiple myeloma cells needed to support cancer cell growth. In similar studies reported in a poster by scientists at Dana-Farber (Senior Author: Dr. Kenneth C. Anderson), experiments were reported demonstrating that Atiprimod inhibits the growth of drug-resistant lines of human multiple myeloma cells, an important requirement for any drug that is developed to treat patients previously treated with chemotherapeutic agents. Importantly, Atiprimod was also shown to inhibit the secretion of key growth factors needed to support growth of multiple myeloma cells. “The data from these two highly-regarded research teams at Dana-Farber and M. D. Anderson, as well as additional research conducted by Callisto scientists, provide the framework for the first clinical trial of Atiprimod in multiple myeloma planned to begin in the next few weeks” said Dr. Gary S. Jacob, CEO of Callisto Pharmaceuticals, Inc.


Atiprimod is Callisto’s lead drug candidate for multiple myeloma. Callisto recently filed an investigational new drug application (IND) on Atiprimod, and a Phase I/IIa clinical trial in multiple myeloma patients is expected to begin shortly.

About Callisto Pharmaceuticals, Inc.

Callisto is a biopharmaceutical company primarily focused on the development of drugs to treat multiple myeloma, other cancers and osteolytic bone disease. Callisto’s lead drug candidate, Atiprimod, is a small-molecule, orally available drug with antiproliferative and antiangiogenic activity. Atiprimod successfully completed Phase I clinical trials in rheumatoid arthritis patients and Callisto plans to enter Atiprimod in a safety and proof-of-principle clinical trial in multiple myeloma patients. The drug is also being explored as an agent to treat osteolytic bone disease. In addition,

Callisto has programs focused on the development of an analog of the human intestinal hormone, uroguanylin, to treat colon cancer, and drugs to protect against staphylococcal and streptococcal bioweapons, protecting against the devastating effects of toxic shock syndrome. Callisto has two operating subsidiaries, Callisto Research Labs, LLC and Synergy Pharmaceuticals Inc. Callisto has an exclusive worldwide license from AnorMED Inc. to develop, manufacture, use and sell Atiprimod. For additional information, visit

Included in this release are “forward-looking” statements. 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. Callisto’s actual results could differ materially from those anticipated in the forward-looking statements as a result of various factors.