Ulcerative Colitis

The securities issued in the private placement have not been registered under the Securities Act of 1933, as amended.

Accordingly, these securities may not be offered or sold in the United States, except pursuant to the effectiveness of a registration statement or an applicable exemption from the registration requirements of the Securities Act.

Callisto has agreed to file a registration statement covering resale of the securities by the private placement investors.

This press release shall not constitute an offer to sell or the solicitation of an offer to buy the securities.

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 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 prov...

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