March 2, 2007

Callisto's Cancer Drug Atiprimod To Be Presented At The Annual Meeting Of American Association Of Cancer Research

Callisto Pharmaceuticals, Inc. (Amex: KAL; Frankfurt: CA4), a biopharmaceutical company primarily focused on the development of drugs to treat cancer and other major health threats, today announced acceptance of an abstract on Atiprimod, the Company's anti-cancer drug candidate, to be presented at the 98th annual meeting of American Association of Cancer Research (, which will be held from April 14-18, 2007 in Los Angeles, CA. The abstract entitled "Deactivation of Akt and STAT-3 Signaling Promotes Apoptosis, Inhibits Proliferation and Enhances Sensitivity of HCC Cells to an anti-cancer agent, Atiprimod" is jointly authored by scientists from Callisto and the Institute of Hepatitis Virus Research.

According to Dr. Kunwar Shailubhai, Senior Vice President of Discovery Research at Callisto Pharmaceuticals and the senior author of the abstract, liver cancer cells that are infected by hepatitis virus B (HBV) and hepatitis virus C (HCV) are more sensitive to anti-proliferative and pro-apoptotic activities of Atiprimod. "Our preclinical data clearly suggest that these preferential activities of Atiprimod are via the downregulation of PI-3 kinase/Akt and Jak/STAT3 pathways, key pathways that are exploited in hepatitis viral-infected liver cancer cells for their growth and survival," notes Dr. Shailubhai. "Importantly, activation of PI-3 Kinase/Akt and Jak/STAT3 pathways is required for tumorigenesis and for cancer-cell proliferation and survival. Thus, inhibitors of these pathways show potential as therapeutic agents against human cancers."

About Atiprimod

Atiprimod is an orally bio-available small molecule drug that displays multiple mechanisms of action. The drug has been shown to be antiangiogenic, inhibit secretion of VEGF and IL-6, elicit an apoptotic response (programmed cellular death), and inhibit phosphorylation of key kinases involved in tumor progression and survival including Akt and STAT3. The drug is presently in two clinical trials: a Phase II trial in advanced carcinoid cancer patients, and a Phase I/IIa human clinical trial in relapsed or refractory multiple myeloma patients. Callisto earlier announced in June, 2006 interim data from a Phase I trial of Atiprimod in advanced cancer patients. The patients who were entered into this trial had growing tumors and symptoms that were no longer controlled by the standard therapies utilized. During treatment, three of the five advanced carcinoid patients had measurable tumor regressions and loss of many of the debilitating symptoms of this disease.

About Callisto Pharmaceuticals, Inc.

Callisto is a biopharmaceutical company focused on the development of new drugs to treat various forms of cancer and other serious afflictions. Callisto's drug candidates in development currently include anti-cancer agents in clinical development, in addition to drugs in pre-clinical development for other significant health care markets, including ulcerative colitis. One of the Company's lead drug candidates, Atiprimod, is in development to treat advanced carcinoid cancer, a neuroendocrine tumor, and relapsed multiple myeloma, a blood cancer. Atiprimod is presently in a Phase II clinical trial in advanced carcinoid cancer patients, and in Phase I/IIa human clinical trials in relapsed or refractory multiple myeloma patients, and advanced cancer patients, respectively. Another anti-cancer drug, L-Annamycin, is being developed as a treatment for forms of relapsed or refractory acute leukemia, a currently incurable blood cancer. Callisto initiated a clinical trial of L-Annamycin in adult relapsed or refractory acute lymphocytic leukemia patients in 4Q 2005. L-Annamycin, a new compound from the anthracycline family of proven anti-cancer drugs, has a novel therapeutic profile, including activity against resistant diseases and significantly reduced cardiotoxicity, or damage to the heart, compared to currently available drug alternatives. Callisto also has drugs in preclinical development for gastro-intestinal inflammation, and cancer. Callisto has exclusive worldwide licenses from AnorMED Inc. and M.D. Anderson Cancer Center to develop, manufacture, use and sell Atiprimod and L-Annamycin, respectively. Callisto is also listed on the Frankfurt Stock Exchange under the ticker symbol CA4. More information is available at

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-K/A for the year ended December 31, 2005, 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.

Callisto Pharmaceuticals, Inc.

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