Biogen Idec Inc. (BIIB) disclosed six more cases of a rare brain infection in multiple sclerosis patients on Tysabri, which it sells with Elan Corp. (ELN), bringing the total number of cases to 55 as of June 7.
The
Cambridge, Mass., biotech company reported no additional deaths in
patients that have developed progressive multifocal leukoencephalopathy,
or PML, keeping the total at 11.
Tysabri
is considered a highly effective therapy for MS, and its sales growth
is important to the future of both Biogen and Elan. But sales have been
slower than first anticipated because of concerns about the risk of PML,
which led to the drug's 18-month market withdrawal beginning in 2005.
The
overall global rate of PML infection is about 0.77 per 1,000 patients,
Biogen said, which falls within the 1-in-1,000 rate previously seen in
clinical trials and implied on the drug's label.
Shares of Biogen added 23 cents Wednesday to $48.35, while the American Depositary Shares of Elan slid 11 cents to $5.04.
Of the 55 cases Biogen reported, 20 were in the U.S., 32 in the European Union and three in other areas.
Biogen provides monthly updates on the number of PML cases in patients taking Tysabri.
A
patient's risk of getting PML increases with the number of monthly
infusions that he or she receives, something the Food and Drug
Administration highlighted in a January safety update. The agency
concluded that the benefits of the medicine continue to outweigh the
risks.
The
most recent monthly update translates to a rate of 1.24 cases per 1,000
for patients on the drug for a year or longer, but rises to 1.76 per
1,000 for those on the drug at least two years.
The
rate of incidence is about 0.35 cases per 1,000 patients on the drug
for between one and two years and 1.47 per 1,000 for those taking the
drug between two and three years.
