Callisto Pharmaceuticals Granted Orphan Drug Designation For Atiprimod To Treat Carcinoid Tumors

NEW YORK, Sept. 26 /PRNewswire-FirstCall/ -- Callisto Pharmaceuticals, Inc. , a biopharmaceutical company primarily focused on the development of drugs to treat cancer, announced today that the Office of Orphan Products Development of the United States Food and Drug Administration (FDA) has granted orphan drug designation to the company’s drug candidate Atiprimod for the treatment of carcinoid tumors. Atiprimod, a small molecule antiangiogenic drug, is being developed by Callisto to treat advanced carcinoid tumors as well as relapsed multiple myeloma patients. Callisto plans to begin a Phase II clinical trial in advanced carcinoid cancer patients in the coming months.

“This marks an important step for Callisto’s Atiprimod program,” commented Callisto Chief Executive Officer Dr. Gary S. Jacob. “Callisto is planning an ambitious program of clinical development of Atiprimod in the carcinoid indication and the designation of orphan drug status gives additional assurance that we are well protected against any potential competition.”

About Orphan Drug Designation

The Orphan Drug Act is intended to encourage development of products for rare diseases affecting fewer than 200,000 people in the United States. Orphan drug designation, along with approval by the FDA for commercialization of Atiprimod, entitles Callisto to seven years of market exclusivity in the United States, provided Callisto continues to meet certain conditions established by the FDA. During the seven-year exclusivity period, the FDA will not accept or approve other applications to market the same medicinal product for the same therapeutic indication.

For products designated as orphan drugs, the FDA not only provides market protection for the developing company, but also provides certain tax credits, eligibility for research grants and protocol assistance, opportunities for regulatory agency assistance on review of clinical protocols, and waiver of the Prescription Drug User Fee Act (PDUFA) filing fee.

About Atiprimod

Atiprimod is in clinical trials for advanced carcinoid tumors and relapsed multiple myeloma (MM). A small-molecule, orally available drug with antiproliferative and antiangiogenic activity, Atiprimod began an open-label Phase I/IIa clinical trial in relapsed MM patients in May 2004, and the trial has been extended to higher dosages of drug. Notably, Atiprimod was found to give encouraging activity in a cohort of carcinoid cancer patients in a Phase I clinical trial in advanced cancer patients. In June 2006 interim results from the trial were released showing that 3 of the 5 patients on the drug gave measurable tumour regressions and loss of debilitating symptoms. Callisto recently announced plans to open a Phase II clinical trial of Atiprimod in advanced carcinoid patients in 3Q 2006.

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 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 and relapsed multiple myeloma, a blood cancer. Atiprimod is presently in Phase I/IIa human clinical trials in relapsed multiple myeloma patients, and advanced cancer patients, respectively. A second drug candidate, L-Annamycin, is being developed as a treatment for forms of relapsed acute leukemia, a currently incurable blood cancer. Callisto initiated a clinical trial of L-Annamycin in adult relapsed acute lymphocytic leukemia patients in 4Q 2005. L-Annamycin, is 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 at http://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-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.

CONTACT: Dan D’Agostino of Callisto Pharmaceuticals, Inc., +1-212-297-0010x227, dagostino@callistopharma.com

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