From: Callisto Pharmaceuticals, Inc.
Published: Tue Jun 28 2005

NEW YORK, NY – June 28, 2005 – Callisto Pharmaceuticals, Inc. (AMEX: KAL), a biopharmaceutical company primarily focused on the development of drugs to treat cancer, announced today that it has received notification from the Office of Orphan Products Development of the United States Food and Drug Administration (FDA) of orphan drug designation for the company’s drug candidate Annamycin for use in the treatment of acute myeloid leukemia (AML).

Initially developed at M.D. Anderson Cancer Center, Annamycin, a second-generation anthracycline, is currently being developed by Callisto to treat both acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) patients. A single-agent clinical trial of Annamycin in adult relapsed ALL patients is expected to proceed shortly. Callisto also plans to initiate a clinical trial of Annamycin in combination with Ara-C in adult relapsed AML patients in 2005.

"We are pleased that the FDA has granted orphan drug designation to Annamycin to treat both AML and ALL patients," said Callisto Chief Executive Officer Dr. Gary S. Jacob. "This is very timely for Callisto, as we are about to embark on an ambitious clinical development program on Annamycin in relapsed leukemia patients. Orphan drug designation for Annamycin to treat AML, in addition to the earlier granting of orphan drug designation for Annamycin to treat ALL, provides additional assurance to the company and its investors that Callisto is well protected against 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 Annamycin, 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 Annamycin

Annamycin, a drug from the anthracycline family, earlier completed a Phase I/IIa trial in refractory leukemia patients. The drug was developed at M.D. Anderson Cancer Center to address limitations associated with other anthracyclines. Annamycin circumvents multiple drug resistance, shows decreased cardiotoxicity, and achieves greater than 95 percent incorporation into liposomes, providing a favorable means of drug administration.

About Callisto Pharmaceuticals, Inc.

Callisto is a biopharmaceutical company 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 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 drug resistant tumors 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-K/A 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.

Investor Relations:
Marty Tullio
McCloud Communications, LLC

Company Contact:
Dan D’Agostino
Callisto Pharmaceuticals, Inc.
212.297.0010 x227

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Company: Callisto Pharmaceuticals, Inc.
Contact Name: Marty Tullio
Contact Email:
Contact Phone: 949 553 9748