A U.S. Food and Drug Administration panel said Monday the agency needs to review a test to determine if patients with chronic myeloid leukemia have a particular type of mutation before taking action on proposed cancer drug Omapro.

The drug, also known by its generic name omacetaxine, is being developed by ChemGenex Pharmaceuticals Ltd. (CXSPY, CXS.AU) to treat a subgroup of patients with CML.

Specifically, the company is seeking approval for Omapro to treat patients with a mutation known as T315I that can develop in some patients after being treated with Gleevec. Gleevec, by Novartis AG (NVS, NOVN.VX) is currently the mainstay of treatment for chronic myeloid leukemia, or CML.

However, the agency said there is no commercially available method to test patients to see if they have the T315I mutation. The agency said 35% of patients in the study didn't have their mutation status confirmed when they entered the study, and that the response of patients in the study to the drug was considered "low."

The FDA asked the panel for advice on whether a diagnostic test that can determine if a patient has a T3151 mutation should be required and reviewed by the FDA before it considers whether to approve Omapro. The panel voted 7 to 1 in favor of the question. The panel didn't vote on whether it thinks the FDA should approve the product.

Adam Craig, ChemGenex's chief medical officer, said the company has a meeting with FDA's medical device division next month to discuss how to get a diagnostic test approved but couldn't speculate on a timeline for approval of the test.

In an interview last month, Greg Collier, ChemGenex's chief executive, explained the T3151 mutation also prevents other drugs approved to treat CML, such as Tasigna, also from Novartis and Sprycel from Bristol-Myers Squibb Co. (BMY). Tasigna and Sprycel are approved for use in patients who don't respond to treatment with Gleevec.

Omapro is designed to work through a different mechanism than Gleevec to keep cancer cells from proliferating by stopping the production of certain so-called short-lived oncoproteins that are present in leukemia cells.

One study involving Omapro involved 81 patients with CML who were all at different stages of the disease. The response rate to the drug ranged from 35% to 86% of patients depending on the phase of the disease, with better responses seen among less sick patients.

Chronic myeloid leukemia is one of four types of leukemia, a type of blood cancer in which abnormal white cells are produced, limiting the body's ability to fight infection. About 5,000 new cases are diagnosed each year in the U.S. according to the National Cancer Institute.

-By Jennifer Corbett Dooren, Dow Jones Newswires; 202-862-9294; jennifer.corbett@dowjones.com
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