Biogen downplays virus threat with MS drug Tysabri

 * 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 Inc BIIB.O on
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Elan Corp Plc ELN.I, was temporarily withdrawn from the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
 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
 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)