ChemGenex Reports Preclinical Data at American Association of Cancer Research (AACR) Annual Conference.

MELBOURNE, Australia & MENLO PARK, Calif. -- ChemGenex Pharmaceuticals Limited (ASX:CXS and NASDAQ:CXSP) announced today the presentation of new preclinical data on its lead compound, Ceflatonin([R]) (homoharringtonine, or HHT), demonstrating its oral bioavailability and further describing the drug's mechanism of action. Ceflatonin is currently in phase 2/3 clinical trials for chronic myeloid leukemia (CML) patients who are resistant to tyrosine kinase inhibitor (TKI) therapy, where the drug is administered by subcutaneous injection. Also presented at the meeting was data supporting the potential of one of ChemGenex's preclinical compounds as a therapeutic agent for cancer patients who are resistant to the chemotherapeutic drug cisplatin.

Each of the preclinical findings were presented as poster presentations at the American Association of Cancer Research (AACR) 98th Annual Meeting in Los Angeles, California.

Highlights of the posters include:

* Data in rodent models showing that Ceflatonin is orally bioavailable. A range of different oral delivery systems were compared with intra-peritoneal (IP) delivery of HHT, and it was found that efficacy was similar via either route. This finding supports the potential development of oral delivery forms in the future, which could provide improved convenience for patients and extended patent protection for ChemGenex. (Abstract 4730).

* New information on the mechanism of action for HHT, which has previously been identified as an inhibitor of protein synthesis. The new data demonstrate that Ceflatonin regulates the binding of transcription factors in a more specific manner than the non-specific protein synthesis inhibitor, cycloheximide. At doses of similar toxicity, cycloheximide affects a larger number of transcription factors than HHT, and the effects of HHT on transcription factors appear to be more specific. This result adds to the growing body of research defining the mechanism of action of Ceflatonin in CML and other leukemias. (Abstract 4843).

* The discovery by a team led by Drs Siddik and Khokhar at the M.D. Anderson Cancer Center in Houston, Texas that in ovarian cancer cells, a ChemGenex preclinical drug candidate CXS299 up-regulates the expression of the tumor suppressor p53 and circumvents resistance to cisplatin, one of the 'standards of care' in the treatment of ovarian cancer. This data further support the potential for CXS299 as a therapeutic agent for patients who have inherent resistance or who develop resistance to cisplatin. (Abstract 3194).

Greg Collier, Ph.D., ChemGenex's Managing Director and Chief Executive Officer said, "While our current focus is on progressing Ceflatonin through the current phase 2/3 clinical trials in CML to support the filing of an initial new drug application (NDA) for this molecule, this data continue to highlight the potential of the ChemGenex pipeline. They demonstrate we have the potential to augment our product portfolio over the coming years not only with enhancements to Ceflatonin, but also with new product candidates for diseases like ovarian cancer that represent significant unmet needs."

Ceflatonin([R]) is a registered trademark of ChemGenex Pharmaceuticals Limited.

About ChemGenex Pharmaceuticals Limited (www.chemgenex.com)

ChemGenex Pharmaceuticals is a pharmaceutical development company dedicated to improving the lives of patients by developing therapeutics in the areas of oncology, diabetes and obesity. ChemGenex harnesses the power of genomics for target discovery and validation, and in clinical trials to develop more individualized therapeutic outcomes. ChemGenex's lead compound, Ceflatonin([R]), is currently in phase 2/3 clinical trials for chronic myeloid leukemia (CML) and Quinamed([R]) is in phase 2 clinical development for prostate, breast and ovarian cancers. The company has a significant portfolio of anti-cancer, diabetes and obesity programs, several of which have been partnered with international pharmaceutical companies. ChemGenex currently trades on the Australian Stock Exchange under the symbol "CXS" and on NASDAQ under the symbol "CXSP".

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