* 95 PML cases, 20 deaths reported since 2007 relaunch
* Estimated incidence of PML per 1,000 patients now 1.16
NEW YORK Feb 18 Ten more patients taking
Biogen Idec's (BIIB.O) multiple sclerosis drug Tysabri
developed the serious brain infection known as PML last month
and there were reports of four more deaths, according to a
monthly update by the U.S. biotechnology company.
The new cases of potentially fatal progressive multifocal
leukoencephalopathy, or PML, were detected between Jan. 7 and
Feb. 2, bringing the total number of confirmed cases to 95 and
deaths to 20 since the drug was reintroduced into the market in
July of 2007, Biogen said.
Biogen, which markets the drug with Ireland-based partner
Elan Corp Plc ELN.I, said the overall rate of PML cases per
1,000 patients has edged slightly higher to 1.16. In November
it had been 1.0.
The number of new PML cases per month has been climbing.
Four new cases were reported in November and six in December.
"We know, and have known for some time, that PML increases
with duration of time you are on therapy," Biogen spokeswoman
Naomi Aoki said. "As we see patients on therapy longer, it's
not surprising that you see new cases."
Tysabri, considered the most important growth driver for
Biogen and Elan, is given by infusion typically one a month.
For patients who have received between one and 12 Tysabri
infusions the incidence of PML is just 0.01 per 1,000. That
rises to 0.4/1,000 for between 13 and 25 infusions and to
1.64/1,000 for patients who have been on the drug between two
and three years, the company said.
"Within these treatment intervals we've seen those numbers
stay fairly steady," Aoki said.
Tysabri was briefly pulled from the U.S. market over
concerns about the brain infection.
But the drug was considered to be so effective compared
with other available treatments that MS patients considered the
risk worth taking and clamored for its return.
Health regulators relented and allowed a relaunch of the
drug with certain restrictions, including close monitoring of
patients and regular reporting of PML cases.
(Reporting by Bill Berkrot; Editing by Richard Chang)