ChemGenex’s Omacetaxine Shows Activity in Refractory CML

LONDON - New Clinical Data Presented at EHA Suggests That Omacetaxine May Provide a Useful Treatment Option for CML Patients Resistant to Multiple TKI Therapies

ChemGenex Pharmaceuticals Limited (ASX:CXS) announced that positive, updated data from its phase 2/3 clinical trial study of omacetaxine in chronic myeloid leukemia (CML) patients with resistance to multiple tyrosine kinase inhibitors (TKIs) was presented at the 14th Congress of the European Hematology Association (EHA) in Berlin, Germany on Saturday.

Dr. Meir Wetzler MD, Chief of the Division of the Leukemia, School of Medicine and Biomedical Sciences, University at Buffalo, Roswell Park Cancer Institute, a lead investigator in the study, presented the data. Dr. Wetzler said, “TKIs are our front line of attack in CML, but significant numbers of patients have developed cross resistance to drugs in this chemical class. As a physician I need alternatives, so it is important to continue the search for new drug entities to treat refractory CML. The data emerging from this study provide encouraging signs that omacetaxine could offer a viable therapeutic option for this patient group.”

Data were presented from 65 patients: 30 in chronic phase, 20 in accelerated phase and 15 in blast phase. Highlights of the data were:

Chronic phase patients - Complete hematologic response (CHR) rate of 80% with a median response duration 7.5 months - Major cytogenetic response (MCyR) rate of 20% with a median response duration 2.7 months Accelerated phase patients - CHR rate of 60% with a median duration 8.9 months Blast phase patients - CHR rate of 40% with a median duration 5.7 months

Tolerability

Investigators reported that omacetaxine is generally well tolerated, and that the most common side effect is reversible and transient myelosuppression.

Commenting on the presentation, Greg Collier, Chief Executive Officer and Managing Director of ChemGenex said, “Omacetaxine has a very different mechanism of action compared to the TKIs, and we have always believed that it may offer the potential to overcome TKI-resistance. The latest results of this study are very encouraging, but this clinical trial is still at an early stage. In the meantime, ChemGenex remains focused on our primary objective of developing omacetaxine as a therapeutic option for CML patients who have developed the T315I mutation. This is one of the most pressing unmet medical needs in the field of CML management.”

Dr. Collier and ChemGenex’s Chief Medical Officer Dr. Adam Craig will host an investor conference call and webcast to discuss the clinical results from both ASCO and the EHA Congress on Thursday 11th of June at 10 am Australian Eastern Standard Time.

Webcast Details Telephone access (toll free) details are below: 1800-131-617 Australia Free Call +61-7-3107-0222 International / Metered Number 0800-446-958 New Zealand Free Call 800-120-4406 Singapore Free Call 800-962-283 Hong Kong Free Call 001-803-011-4106 Indonesia Free Call 0044-22-132-558 Japan Free Call 866-746-2596 USA/Canada Free Call 0800-376-8339 UK Free Call 0800-330-2094 Germany Free Call 0805-111-476 France Free Call 0800-001-230 Switzerland Free Call

Online: services.choruscall.com/links/chemgenex090611.html

About the trial

CGX-635-CML-203 is a phase 2/3 open-label study using omacetaxine as a subcutaneous injection for the treatment of patients with chronic myeloid leukemia (CML) who are intolerant to or have failed multiple TKIs.

Omacetaxine Overview

Omacetaxine mepesuccinate is a first-in-class cetaxine with demonstrated clinical activity as a single agent in a range of hematological malignancies. Omacetaxine has a novel mechanism of action, specifically binding to the ribosomal A-site cleft and inhibiting protein translation of short-lived oncoproteins that are upregulated in leukemic cells (particularly Cyclin-D1, Mcl-1 and c-Myc). As omacetaxine acts independently of tyrosine kinase inhibitors, it may have a therapeutic advantage for patients who have developed resistance to TKIs. Omacetaxine is administered subcutaneously.

About ChemGenex Pharmaceuticals Limited (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, is currently in phase 2/3 clinical trials for chronic myeloid leukemia (CML). ChemGenex has a second anticancer compound, amonafide dihydrochloride (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”. For additional information on ChemGenex Pharmaceuticals, please visit our web site at www.chemgenex.com.

Details on the clinical trials can be accessed from the following websites;

clinicaltrials.gov/ct2/show/NCT00375219?term=homoharringtonine&rank=9

and www.tkiresistantcmltrials.com

Safe Harbor Statement

Certain statements made herein (including for this purpose sites to which a hyperlink has been provided) that use the words “estimate”, “project”, “intend”, “expect”, “believe” and similar expressions are intended to identify forward-looking statements within the meaning of the US Private Securities Litigation Reform Act of 1995. These forward-looking statements involve known and unknown risks and uncertainties which could cause the actual results, performance or achievements of the company to be materially different from those which may be expressed or implied by such statements, including, among others, risks or uncertainties associated with the development of the company’s technology, the ability to successfully market products in the clinical pipeline, the ability to advance promising therapeutics through clinical trials, the ability to establish our fully integrated technologies, the ability to enter into additional collaborations and strategic alliances and expand current collaborations and obtain milestone payments, the suitability of internally discovered genes for drug development, the ability of the company to meet its financial requirements, the ability of the company to protect its proprietary technology, potential limitations on the company’s technology, the market for the company’s products, government regulation in Australia and the United States, changes in tax and other laws, changes in competition and the loss of key personnel. These statements are based on our management’s current expectations and are subject to a number of uncertainties that could change the results described in the forward-looking statements. Investors should be aware that there are no assurances that results will not differ from those projected.

Contacts ChemGenex Information Dr. Greg Collier CEO and Managing Director Cell (Australia): +61-419-897501 Cell (USA): +1-650-200-8145 Email: collier@chemgenex.com Media Relations - Australia Rebecca Wilson Buchan Consulting Tel: +61(0)3-9866-4722 Cell: +61(0)417-382-391 Email: rwilson@bcg.com.au Media Relations - UK Jane Brearley / Hayley Raffill Waggener Edstrom Tel: +44-207-7632-3800 Email: jbrearley@waggeneredstrom.com hraffill@waggeneredstrom.com

Source: ChemGenex Pharmaceuticals Limited

Contacts: ChemGenex Information: Dr. Greg Collier, CEO and Managing Director, Cell (Australia): +61-419-897501, Cell (USA): +1-650-200-8145, Email: collier at chemgenex.com; Media Relations - Australia: Rebecca Wilson, Buchan Consulting, Tel: +61(0)3-9866-4722, Cell: +61(0)417-382-391, Email: rwilson at bcg.com.au; Media Relations - UK: Jane Brearley / Hayley Raffill, Waggener Edstrom, Tel: +44-207-7632-3800, Email: jbrearley at waggeneredstrom.com, hraffill at waggeneredstrom.com