New Details on Suspension of MS Drug Tysabri
3 Patients in Clinical Trials Developed Rare Disease; 2 Died
WebMD News Archive
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
Doctors' Advice for Patients
Tysabri is given by injection every four weeks. That would mean that
patients who took the drug only while it was on the market got a maximum of one
to three doses, Koralnik tells WebMD.
"We would think they are not at any risk of developing PML now if they
haven't manifested any overt neurological disease different from their
baseline," he says.
Patients should talk to the doctors and have their blood screened, says
Annette Langer-Gould, MD, of Stanford University medical school's neurology
department. Langer-Gould, who also serves in Stanford's department of health
research and policy, contributed to a journal report on one of the confirmed
'Very Rare' Disease
PML is "very rare," even in people with weakened immune systems,
People with MS are not believed to be at higher risk for PML, and the
disease is not thought to be contagious, says the FDA's web site.
The patient who survived the confirmed case of PML temporarily had a
worsening of his symptoms about three months after stopping Tysabri. What may
have happened, says Koralnik, is that the patient's white blood cells were able
to get back into the brain at that point to fight the virus.
"It's clear that Tysabri and other medications of this class are
extremely promising to treat a variety of crippling conditions for which there
is no cure," says Koralnik. "But we have to learn, move forward, and
understand better ... the exact mechanisms to the reactivation of this virus, how
to prevent it in the future, and how to monitor for such reactivation."