SOURCE: Callisto Pharmaceuticals, Inc.

May 05, 2005 07:00 ET

Callisto Pharmaceuticals Announces Animal Data on Drug for Inflammatory Bowel Disease

NEW YORK, NY -- (MARKET WIRE) -- May 5, 2005 -- Callisto Pharmaceuticals, Inc. (AMEX: KAL), a biopharmaceutical company primarily focused on the development of drugs to treat cancer, today announced the results of animal studies on SP304, Callisto's drug for treatment of inflammatory bowel disease (IBD) and other gastrointestinal (GI) disorders. SP304 is an orally deliverable, highly stable peptide, which acts locally in the GI tract and is not absorbed into the body. The drug is an analog of native human peptide uroguanylin, a guanylate cyclase receptor agonist (GCRA) normally produced in the intestinal tract, but which is dramatically under-expressed under pathological conditions.

In collaboration with Dr. Scott Plevy, a clinical gastroenterologist at the University of Pittsburgh Medical Center, SP304 was shown to be effective in preliminary experiments conducted in an inducible animal model of colitis, the TNBS murine model. Additional pre-clinical experiments are underway to further define the drug's therapeutic potential.

"SP304 is biologically more potent than uroguanylin and, unlike uroguanylin, it exists in a single biologically active conformation, making it easier to synthesize and manufacture," said Dr. Kunwar Shailubhai, Senior Vice President, Discovery Research, of Synergy Pharmaceuticals, a wholly owned subsidiary of Callisto Pharmaceuticals. "These features distinguish SP304 from any other currently known GCRA and make the compound suitable for drug development."

"We are very encouraged by these data from Dr. Scott Plevy's laboratory on SP304," stated Dr. Gary S. Jacob, Chief Executive Officer of Callisto. "Dr. Plevy is an internationally recognized researcher in IBD, and has been a principle investigator on a number of multi-center clinical trials in IBD. As we stated in our corporate goals to shareholders in February of this year, we are eager to move our pre-clinical programs forward towards the clinic."

The company anticipates the initiation of pre-clinical development of SP304 for an Investigational New Drug application after completion of the remaining animal studies.

About Guanylate Cyclase Receptor Agonist (GCRA) Program

Callisto's GCRA program is focused on a drug to treat GI inflammatory diseases. Callisto's patented technology covers development of agonists that are superior to uroguanylin. Callisto's drug candidate, SP304, has demonstrated superior biological activity, enhanced stability and superior pH characteristics. In earlier studies conducted by Dr. Kunwar Shailubhai, production of uroguanylin was found to be reduced in colon cancer patients, indicating that lowered expression of uroguanylin is a primary cause of colon carcinogenesis in humans. In addition, oral administration of uroguanylin in mice that develop high levels of polyps was shown to substantially reduce polyp formation and progression to adenocarcinoma (Cancer Research 60: 5151-51577, 2000 Experiments conducted with SP304 demonstrate that this drug clearly outperforms uroguanylin in a series of in-vitro and in-vivo experiments.

About Callisto Pharmaceuticals, Inc.

Callisto is a biopharmaceutical company primarily focused on the development of drugs to treat cancer. Callisto has two lead drugs in clinical development, Annamycin to treat relapsed leukemia, and Atiprimod to treat relapsed multiple myeloma. Callisto intends to initiate a Phase IIb clinical trial of Annamycin in relapsed acute lymphoblastic leukemia patients in mid 2005. Annamycin, a drug from the anthracycline family, has a novel therapeutic profile, including activity against resistant diseases and significantly reduced cardiotoxicity. 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

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, 2004,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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