June 16, 2008

ChemGenex’s Omacetaxine Demonstrates Activity in CML Patients Who Have Failed Therapy With Multiple Tyrosine Kinase Inhibitors

ChemGenex Pharmaceuticals (ASX:CXS) (NASDAQ:CXSP) announced today the presentation of positive preliminary results from a phase 2 study of omacetaxine mepesuccinate (formerly known as Ceflatonin(R)) in chronic myeloid leukemia (CML) patients who have failed therapy with at least two tyrosine kinase inhibitors (TKIs). These data represent the first findings to be presented from this ongoing study, conducted in patients with or without BCR-ABL mutations. The data presented complement the findings from the company's previously reported phase 2/3 study of omacetaxine in CML patients with the T315I mutation.

ChemGenex's Senior Vice-President and Chief Medical Officer Dr. Adam Craig presented the data on behalf of a team including investigators from ChemGenex and leading U.S. and European research centers in a poster session at the European Hematology Association (EHA) Annual Congress in Copenhagen, Denmark.

To date, 28 patients have been enrolled in the study, and data were presented from 12 evaluable patients: 4 in chronic phase, 2 in accelerated phase and 6 in blast phase. Highlights of the data include:

-- Hematologic responses in all chronic and accelerated phase patients.

-- Complete hematologic responses in 3 out of 4 chronic phase patients and 2 out of 2 accelerated phase patients.

-- Cytogenetic responses in 1 out of 4 chronic phase patients and 1 out of 2 accelerated phase patients.

-- Hematologic responses in 2 out of 6 blast phase patients.

-- Omacetaxine therapy is associated with myelosuppression, which is manageable and reversible.

"We are delighted with this very positive early data from the multiple TKI resistance trial," said Dr. Greg Collier, ChemGenex's Managing Director and Chief Executive Officer. "Our poster at the ASCO conference in Chicago two weeks ago reported durable clinical responses in CML patients with the T315I mutation and these new data support our belief that omacetaxine, acting through an independent mechanism of action, offers a new therapeutic alternative to the growing number of CML patients who become resistant to TKI therapy." Tyrosine kinase inhibitors such as imatinib, dasatinib and nilotinib target the Bcr-Abl protein and are the current approved therapies for CML, but an increasing number of patients are developing resistance to these agents.

"The knowledge we are gaining from our two major clinical trials gives us confidence in the potential of omacetaxine to treat CML patients for whom there are few treatment options due to the limitations of tyrosine kinase inhibitor treatments," said Dr. Collier. "We are on course to commence the filing of our rolling NDA submission to the FDA in mid 2008, starting with the non-clinical section. We also remain on track to achieve our enrollment targets within the year, and to complete our rolling NDA submission in mid 2009."

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

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). 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".

Details on the clinical trials can be accessed from the following websites; http://clinicaltrials.gov/ct2/show/NCT00375219?term= homoharringtonine&rank=9 (Due to its length, this URL may need to be copied/pasted into your Internet browser's address field. Remove the extra space if one exists.) and http://www.tkiresistantcmltrials.com.

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