Callisto Receives Approvals from Three Clinical Research Sites to Advance Clinical Trial of Atiprimod; Institutional Review Board Approvals Enable Study of Anti-Cancer Drug Candidate at Higher Dosage Levels.

NEW YORK -- Callisto Pharmaceuticals, Inc. (AMEX:KAL) (FWB:CA4), a developer of new drug treatments in the fight against cancer and other major health threats, has received approval from three of its clinical research sites to advance the clinical trial of its anti-cancer drug candidate Atiprimod to higher dosage levels under the Company's program to develop the drug as a treatment for the serious blood cancer multiple myeloma.

The approval from the institutional review boards (IRB) of three clinical research sites approved Callisto's amended protocols to study Atiprimod at the higher doses. The Phase I/IIa studies conducted thus far have not demonstrated a maximum tolerated dose (MTD). Some positive therapeutic effect, however, was observed even at those first dosage levels.

The continuation of the studies will enable the researchers to use higher doses of Atiprimod as they study the drug's efficacy as a treatment for multiple myeloma. Additional approvals from other clinical sites are expected to be forthcoming.

"This next wave of research is where we'll expect to see Atiprimod showing some significantly positive activity against multiple myeloma along with further safety data," said Dr. Donald Picker, Callisto's Executive Vice President of Research and Development.

Atiprimod is presently in two Phase I/IIa clinical trials: 1) relapsed or refractory multiple myeloma patients, and 2) advanced cancer patients. Callisto recently announced that based on a clear response in a patient with carcinoid cancer, along with additional encouraging data in other carcinoid patients, the Company plans to initiate a Phase I/II clinical trial specifically in carcinoid patients.

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 and biodefense. One of the Company's lead drug candidates, 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, 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, and advanced carcinoid cancer. Atiprimod is presently in Phase I/IIa human clinical trials in relapsed multiple myeloma patients, and advanced cancer patients, respectively. 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 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.