ChemGenex Investigators Report Activity of Omacetaxine in Imatinib-Resistant Chronic Myeloid Leukemia Patients With the T315I Mutation.

Complete Hematological and/or Complete Cytogenetic Responses in 64% of Chronic Phase Patients

Conference Call to Be Held on Thursday, December 13 Australian Eastern Daylight Time (Wednesday, December 12 in the USA and Europe)

MELBOURNE, Australia & MENLO PARK, Calif. -- ChemGenex Pharmaceuticals (ASX:CXS) (NASDAQ:CXSP) announced today that positive clinical data from the first 21 patients enrolled in its ongoing phase 2/3 trial of omacetaxine mepesuccinate (formerly known as Ceflatonin([R])) were presented over the weekend at the American Society of Hematology (ASH) Annual Meeting in Atlanta, Georgia.

The poster presentation, authored by a team of leading international hematologists, reported both complete hematologic and cytogenetic responses lasting more than 1 year in imatinib (Gleevec([R]))-resistant chronic myeloid leukemia (CML) patients with the T315I mutation. The T315I mutation causes resistance to imatinib and second-generation tyrosine kinase inhibitors and is acknowledged as a major therapeutic challenge in the treatment of CML.

Data were presented from 21 patients: 11 in chronic phase, 4 in accelerated phase and 6 in blast phase. Highlights of the data were:

* Hematologic and/or cytogenetic responses in 91% of chronic phase patients on trial.

* Complete hematologic responses (CHR) in 45% of chronic phase patients, complete cytogenetic responses (CCyR) in 18% of chronic phase patients.

* Hematologic responses in 100% of accelerated phase patients and 34% of blast phase patients, cytogenetic responses in 25% of accelerated phase patients.

* Complete disappearance of the T315I mutation clone in 38% of evaluable patients.

* Two chronic phase patients maintained their clinical response for more than 12 months.

* Reversible and transient myelosuppression was the most common side effect, with grade 3 or 4 toxicity observed in around 60% of patients.

* Few other side effects were reported and the clinical investigators concluded that omacetaxine is generally well tolerated, and that myelosuppression is usually transient and reversible and rarely results in serious clinical complications.

"We are delighted that omacetaxine has been shown to have such a beneficial effect on a significant number of patients with the T315I mutation," said Dr. Greg Collier, ChemGenex's Managing Director and Chief Executive Officer. "The issue of BCR-ABL mutations and subsequent resistance to tyrosine kinase inhibitor therapy is growing, and these impressive clinical data reinforce the potential of omacetaxine. Importantly, omacetaxine acts via a completely different mechanism to the tyrosine kinase inhibitors, independent of the BCR-ABL protein."

ChemGenex's Chief Medical Officer Dr. Adam Craig is very pleased with the data. "The interim clinical data are very encouraging as omacetaxine is showing signs of clinical activity in the CML T315I+ patient population. Patients with the T315I mutation have very limited therapeutic options, as no approved CML therapies are effective against this mutation."

Dr. Collier will host an investor conference call to discuss the clinical results on Thursday, December 13 at 9:30am Australian Eastern Daylight Time (Wednesday, December 12 in the USA and Europe).

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Ceflatonin([R]) is a registered trade-mark of ChemGenex Pharmaceuticals Limited.

Gleevec([R])/Glivec([R]) is a registered trade-mark of Novartis AG.

About ChemGenex Pharmaceuticals Limited (http://www.chemgenex.com)

ChemGenex Pharmaceuticals is a pharmaceutical development company dedicated to improving the lives of patients by developing personalized oncology medicines. ChemGenex harnesses the power of genomics both to discover novel targets and drug compounds, and in clinical trials to develop more individualized treatment outcomes. ChemGenex's lead compound, omacetaxine mepesuccinate (formerly known as Ceflatonin[R]), is currently in phase 2/3 clinical trials for chronic myeloid leukemia (CML) where it has demonstrated single-agent efficacy against drug-resistant disease, as well as synergistic activity with the leading marketed compound. ChemGenex has a second anticancer compound, amonafide dihydrochloride (formerly known as Quinamed[R]) which is in phase 2 clinical development for various solid cancers, and a portfolio of assets in pre-clinical development. ChemGenex currently trades on the Australian Stock Exchange under the symbol "CXS" and on NASDAQ under the symbol "CXSP".

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