Tysabri, the MS Drug Haunted by Deadly Side Effect, Doesn’t Look So Deadly Anymore

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this fall, in which the number of cases of PML appears to have gone through a sharp increase. There were 13 cases confirmed in an FDA notice on September 17, and the number climbed to 23 when European regulators issued an update on October 23. The latest tally now stands at 27, Sandrock said in a Nov. 11 interview (and which was confirmed again yesterday by company spokeswoman Naomi Aoki). Based on this evolving body of evidence, the FDA updated the Tysabri prescribing information earlier this month to say that the risk appears to increase as patients stay on the drug for longer periods of time.

But even as more cases get diagnosed, I wanted to know why there hasn’t been a corresponding increase in the number of deaths. The chart shows more than 80 percent of patients diagnosed with PML since the drug came back on the market in July 2006 are still alive. Lots of doctors also want to know what’s happening to those patients who get PML, but still live. Biogen isn’t releasing a patient-by-patient breakdown of what is happening to them all, but its medical affairs staff is answering those questions from physicians, Aoki says.

Some of the patients are severely disabled, Sandrock says, but a few—he wouldn’t say exactly how many of the 27 cases—have recovered and even feel strong enough to return to work. The New England Journal of Medicine recently published an article about one case of PML in which a patient became critically ill with PML, but recovered.

“Back when I trained as resident, we didn’t know much about it, but it was assumed that PML was almost always fatal,” Sandrock says. “But the survival rates appear to have changed. The outcome from PML is not certain death. Some have done well, and others, not so well.”

Of course, this isn’t the only way to look at the PML risk. The drug’s makers and regulators are looking at databases that factor in different variables, like the number of patients who have been on the drug for more than a year, more than two years, more than three years, and so forth. Those figures are what led regulators to add new language to the label that says the risk increases over time. Sandrock emphasized that even though the risk does increase, it’s still within the 1-in-1,000 rate that patients were warned about back in July 2006, even for patients who have been on the drug since … Next Page »

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