Callisto Pharmaceuticals Announces Poster Presentation on Atiprimod at Major Scientific Meeting in December; Research on Atiprimod's Effect on Leukemia Cells to Be Presented at American Society of Hematology Annual Meeting.

NEW YORK -- Callisto Pharmaceuticals, Inc. (AMEX:KAL)(FWB:CA4), a developer of new drug treatments in the battle against cancer and other serious health threats, today announced that an abstract describing research into the effect of its new anti-cancer drug Atiprimod on leukemia cancer cells has been accepted for poster presentation at the annual meeting of the American Society of Hematology (ASH), December 10 -- 13, 2005, in Atlanta, Georgia.

ASH, the leading scientific organization for hematological medicine and other research, has additionally accepted two other abstracts on Callisto's Atiprimod research for high-profile oral presentations at the annual meeting.

The abstract selected for poster presentation was authored by scientists at the University of Texas M.D. Anderson Cancer Center. It describes studies of Atiprimod on acute myeloid leukemia (AML) cells. The researchers were able to show that Atiprimod inhibits growth of AML cells and blast proliferation, but importantly, does not have significant effect on normal blood progenitor cells. In summary, the M.D. Anderson researchers suggest that further evaluation of Atiprimod in clinical trials of AML and myelodisplastic syndrome should be considered.

The abstract (#2462) is available on the ASH Web site at www.hematology.org.

About the American Society of Hematology

The mission of the American Society of Hematology (ASH) is to further the understanding, diagnosis, treatment, and prevention of disorders affecting the blood, bone marrow, and the immunologic, hemostatic and vascular systems, by promoting research, clinical care, education, training, and advocacy in hematology. For the past four decades, ASH has sponsored its annual meeting, the premier annual education and scientific event in the field of hematology, and has published Blood, the Journal of the American Society of Hematology, which is the most cited peer-reviewed publication in the field. Each December, the Society's annual meeting provides hematologists from around the world a forum for discussing critical issues in hematology. Nearly 20,000 clinicians, scientists, and others attend the four-day meeting, which consists of a superb educational program and cutting-edge scientific sessions. Oral and poster presentations, which are chosen by peer-reviewers from abstracts submitted prior to the annual meeting, are featured at the annual meeting and contain the latest and most exciting developments in scientific research. For more information, please visit http://www.hematology.org.

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 a range of other significant health care market segments, including biodefense. One of the Company's lead drug candidates, L-Annamycin, is being developed as a treatment for forms of relapsed leukemia, a currently incurable blood cancer. Callisto intends to initiate a clinical trial of L-Annamycin in relapsed acute lymphoblastic 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. Another anti-cancer drug, Atiprimod, is in development to treat relapsed multiple myeloma, a blood cancer. Atiprimod has entered Phase I/IIa human clinical trials in relapsed multiple myeloma patients. Callisto also has drugs in preclinical development for 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 L-Annamycin, respectively. For investor-specific information about Callisto, including recent news and stock price data, please visit http://www.trilogy-capital.com/tcp/callisto/. For an Investor Fact Sheet about Callisto, please visit http://www.trilogy-capital.com/tcp/callisto/factsheet.html. To view an informational presentation of the Company's development pipeline of drug candidates, visit http://www.trilogy-capital.com/tcp/callisto/powerpoint.html. Callisto is also listed on the Frankfurt Stock Exchange under the ticker symbol CA4. For additional information, visit 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, 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.