Callisto Anti-Cancer Drug Atiprimod Chosen for Second High-Profile Oral Presentation at American Society of Hematology Meeting; Newly Released Research Paper Details Anti-Tumor Activity of Atiprimod in Animal Study.

NEW YORK -- Callisto Pharmaceuticals, Inc. (AMEX:KAL)(FWB:CA4), a developer of new drug treatments in the fight against cancer and other serious health threats, today announced that its anti-cancer drug candidate Atiprimod has been further recognized by the scientific community with selection for a second Oral presentation of research data, abstract (#249), at the annual meeting of American Society of Hematology (ASH), the field's most important scientific organization, to be held next month in Atlanta, GA. E[acute accent]Callisto's research collaborators at Dana-Farber Cancer Institute will present findings of an animal-based study to investigate the effect of Atiprimod on multiple myeloma tumors, a serious, currently incurable form of blood cancer. The animal study, conducted by researchers at Dana-Farber, observed that Atiprimod produced experimentally significant reduction in tumor levels. E[acute accent]"Callisto is pleased to have a second abstract dealing with Atiprimod chosen for oral presentation at the ASH annual meeting," said Dr. Gary S. Jacob, CEO and Chief Scientific Officer of Callisto. "This second paper deals with Atiprimod's anti-tumor activity in elegant models of multiple myeloma developed by researchers at Dana-Farber, as well as evaluation of genes that are affected in multiple myeloma cells exposed to the drug. The Atiprimod findings are very encouraging, and we are gratified again that our peers in the scientific community have deemed this research worthy of the particular notice made possible by this oral presentation at the ASH conference." E[acute accent]The newly-announced oral presentation at the ASH meeting will cover not only information released in the abstract (#249), but additional research data obtained subsequent to submission of the abstract. The entire abstract is now available on the ASH Web site, www.hematology.org. The meeting is scheduled for December 10-13, 2005, in Atlanta, Georgia. The oral presentation will be delivered at 8:00 am on Monday, December 12, in the Sidney Marcus Room of the World Congress Center in Atlanta, GA, by Dr. Paola Neri of the Dana-Farber Cancer Institute. It is entitled: "In Vivo Anti-Tumor Activity of Atiprimod on SCID Models of Multiple Myeloma." E[acute accent]Callisto previously announced that a separate oral presentation dealing with the results from the Phase I/IIa clinical trial of Atiprimod in refractory or relapsed multiple myeloma patients will be delivered at 5 pm on December 11, in an Oral Session entitled: "Multiple Myeloma: Novel Therapeutic Approaches" in the Sidney Marcus Room of the World Congress Center in Atlanta, GA. E[acute accent]The newly-announced abstract, #249, describes Atiprimod's activity in three mouse models of human multiple myeloma in addition to gene expression profiling data observed on cells exposed to Atiprimod. One of the animal models evaluated the effect of Atiprimod on human multiple myeloma cells in a human bone marrow microenvironment. In this model, mice were implanted with a human fetal bone chip engrafted with multiple myeloma cells and treated i.p. with Atiprimod (40 mg/kg) or vehicle alone (PBS) for two weeks. The researchers observed a 60% reduction in the indicator of anti-tumor activity in mice treated with Atiprimod versus control group. To evaluate effects of Atiprimod on primary patient cells in a human microenvironment, mice were engrafted with patient multiple myeloma cells (IgG gamma) and treated i.p. with Atiprimod (50 mg/kg) or vehicle alone (PBS) for 4 weeks. Treatment with Atiprimod induced a reduction in both human IgG and gamma light chain levels in mouse sera, whereas levels of both proteins continued to rise in mice treated with vehicle alone. The molecular changes in multiple myeloma cells induced by Atiprimod were also evaluated using gene expression profiling of multiple myeloma cells exposed to Atiprimod. Atiprimod induced significant down-regulation of genes involved in growth and cell-cycle control, adhesion, cell-signalling pathways, up-regulation of genes implicated in apoptotic cascades and in negative regulation of signal transduction.

E[acute accent]About the American Society of Hematology

E[acute accent]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.

E[acute accent]About Callisto Pharmaceuticals, Inc.

E[acute accent]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.

E[acute accent]Forward-Looking Statements

E[acute accent]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.