New Details on Suspension of MS Drug Tysabri
3 Patients in Clinical Trials Developed Rare Disease; 2 Died
June 9, 2005 -- New information has surfaced about the rare but often lethal
disease that prompted the removal of Tysabri, a new multiple sclerosis (MS)
drug. At least three cases have been identified.
Tysabri was approved by the FDA last November. In late February,
The suspension followed reports of one confirmed and one suspected case of
progressive multifocal leukoencephalopathy (PML), a rare but often lethal viral
disease of the central nervous system.
Now, three cases of PML have been confirmed; two of those were fatal. All
three confirmed cases occurred in people who had taken Tysabri for more than
two years in clinical trials. Two patients were also taking another MS drug
called Avonex, according to reports in The New England Journal of
Medicine's July 28 edition.
Possible 4th Case
There have also been media reports of a possible fourth case of PML.
However, that "is still being reviewed and has not been confirmed,"
says FDA spokeswoman Lenore Gelb.
Gelb tells WebMD that Biogen Idec, a WebMD sponsor, notified the FDA of an
adverse event experienced by a fourth patient who had been taking Tysabri and
Avonex. FDA documents show that the patient was a 48-year-old woman, but it's
not yet known if she had PML.
Biogen Idec spokeswoman Amy Brockelman says a newspaper headline last week
incorrectly reported that the fourth patient was dead. The patient is not dead,
and Biogen's safety evaluation of the drug is "ongoing," Brockelman
What's Known So Far
All three confirmed cases occurred in people who had been taking Tysabri for
more than two years as part of clinical trials of the drug, says Igor Koralnik,
MD, associate professor of neurology at Harvard Medical School.
That's much longer than the handful of months in which Tysabri was on the
market, says Koralnik, who co-wrote a journal editorial about Tysabri and also
directs the HIV/Neurology Center at Boston's Beth Israel Deaconess
It's not known if the combination of drugs in two of the confirmed cases
might have been important or if the association was with Tysabri alone, says
Two of the three confirmed cases were MS patients. The third was a
60-year-old man with Crohn's disease. His death was originally attributed to
About 3,000 people took part in the clinical trials, which included patients
with MS, Crohn's disease, and rheumatoid arthritis, says a Biogen Idec