ChemGenex Licenses Targeted Platinum IV Compound from the University of Texas M. D. Anderson Cancer Center.

MELBOURNE, Australia & MENLO PARK, Calif. -- New molecule is active in cancer cells resistant to existing platinum II agents

ChemGenex Pharmaceuticals Limited (ASX:CXS) announced today that it has licensed a novel platinum (IV) agent from The University of Texas M. D. Anderson Cancer Center in Houston, Texas, one of the world's most respected cancer research and treatment institutions. The patented molecule, now called CXS299, is a platinum (IV) anti-cancer agent invented by Zahid H. Siddik, Ph.D. and Abdul R. Khokhar, Ph.D., professors in the Department of Experimental Therapeutics at M. D. Anderson Cancer Center. CXS299 is active against cancer cells resistant to approved platinum-based therapies and possesses unique properties that may allow physicians to target patients who are most likely to benefit from therapy.

Ground-breaking advance

CXS299 is a platinum (IV) drug, which has an enhanced level of activity against cancer cells that have the wild type p53 gene. In many disease types, such as ovarian, breast, testicular and non-small lung cancer, up to 45-90% of patients who fail chemotherapy have wild type p53 in their tumor cells and typically, these patients are highly resistant to additional therapies. By targeting tumors with the wild type p53 gene, ChemGenex believes that it will be able to identify patients more likely to respond to therapy, and to enhance the clinical outcomes for these patients.

CXS299 selectively blocks tumor cells in G1 phase of the cell cycle, which makes the agent unique, more potent and less prone to cross-resistance compared to approved platinum therapies. "This compound represents an exciting, mechanism-based development that takes advantage of pre-existing wild-type p53 gene in both sensitive and resistant tumors. It is the result of over ten years of intense collaborative research effort at M. D. Anderson to identify novel therapeutic approaches to overcome platinum (II) drug resistance," said Dr. Siddik.

"We are delighted that we have been able to consolidate our relationship with The University of Texas M. D. Anderson Cancer Center by in-licensing CXS299, and are confident that our strong track record of progressing compounds through clinical development assisted us in gaining access to this exciting compound," said Greg Collier, Ph.D. chief executive officer and managing director of ChemGenex. "CXS299 represents an excellent opportunity to exploit the genomic understanding of cancer biology to develop better and more targeted therapies. CXS299 is currently in late pre-clinical development and further consolidates our anti-cancer pipeline that currently has two compounds in Phase II clinical development."

Clinical context

One of the dominant classes of chemotherapies for solid tumors is the platinum (II) class with worldwide sales exceeding $1.7 billion in 2003. Despite the clinical success of these compounds, a significant number of patients eventually develop resistance to platinum (II) therapy and there is an urgent need for improved new therapies.

The p53 tumor suppressor protein is a key controlling protein in inducing cell death by many established therapeutic anticancer drugs, and its improper functioning is the cause of treatment failure. It is estimated that mutations in the p53 gene are associated with at least half of human cancers, and are the basis of treatment failures. Current drugs target the complex cascade of events associated with these mutations. However, drug resistance is more severe when refractory cancers retain the 'wild type' (non-mutant) p53 gene, and poses a major dilemma in their clinical management.

About ChemGenex Pharmaceuticals Limited (www.chemgenex.com)

ChemGenex Pharmaceuticals is a gene-based pharmaceutical company dedicated to improving the lives of patients by developing therapeutics in the areas of oncology, diabetes, obesity, and depression. ChemGenex currently has two compounds in Phase II clinical trials, Ceflatonin(R) for leukemia and Quinamed(R) for solid tumors, and has a significant portfolio of anti-cancer, diabetes, obesity and depression programs. The company's diabetes and obesity program is partnered with Merck KGaA and the depression program is partnered with Vernalis plc. ChemGenex currently trades on the Australian Stock Exchange under the symbol "CXS".

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