* Biogen sees no link between JV virus level and PML
* Says NEJM study small with no PML cases involved
BOSTON, Sept 10 (Reuters) - Biogen Idec Incon Thursday downplayed a report that found its multiple sclerosis treatment Tysabri awakens and strengthens a virus that causes a potentially fatal brain disease.
Evan Beckman, Biogen's senior vice president of Immunology Research and Development, said the biotechnology company has not found any correlation between the level of JC virus in the blood or urine and the likelihood of a patient developing the rare brain infection progressive multifocal leukoencephalopathy, or PML.
"We haven't seen any predictive value of this even in patients who have developed PML," Beckman told investors at the Thomas Weisel Partners Conference in Boston.
The report on Tysabri's potential impact on the JV virus appeared in the New England Journal of Medicine (NEJM).
Beckman noted that the study in the NEJM report was very small and that none of the patients developed PML. He called the results "interesting," but said he is not sure to what extent they can be generalized.
In many ways it would be helpful to Biogen if they could be generalized. The company would benefit from having a blood or urine test that could predict which subset of patients might have a greater risk of developing PML.
Tysabri, which is co-marketed by Biogen and Irish drugmaker Elan Corp Plc, was temporarily withdrawn from the market in 2005 after it was linked with PML cases. It was brought back in 2006 with stricter safety warnings following a clamor from multiple sclerosis patients who felt strongly that the benefit of the drug on their daily lives outweighed the PML risks.
Dr. Igor Koralnik of Harvard Medical School and Beth Israel Deaconess Medical Center and colleagues studied 19 multiple sclerosis patients just starting Tysabri. Urine samples from the 19 patients showed levels of the JC virus shot up after a year of taking Tysabri, they noted in the NEJM report.
Beckman said Cambridge, Massachusetts-based Biogen has conducted similar tests on much larger patient groups and has not been able to find a correlation.
The company is examining a myriad of possible factors -- from genes to geography -- that might help them understand the elements that come together in a patient who develops PML, since it appears JC virus concentration levels alone are not predictive.
Tysabri is widely considered to be Biogen's most important product and driver of future growth.
At the end of June, more than 43,000 patients were taking Tysabri. Biogen had originally predicted 100,000 patients would be on the drug by the end of 2010, but physician concerns about Tysabri's safety have caused the company to retract that prediction. It still says 100,000 is a reasonable target, but not within that time frame. (Reporting by Toni Clarke, additional reporting by Bill Berkrot in New York, editing by Matthew Lewis)
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