Possible fourth death tied to Tysabri
The Globe obtained the report of the unconfirmed case under the Freedom of Information Act.
If the case is confirmed, it could make it more difficult to for Biogen Idec and Elan, co-marketers of the drug, to convince the FDA that Tysabri is safe. Because the disease, progressive multifocal lekoencephalopathy (PML), is so rare, each additional confirmed case magnifies the drug's potential risks.
The possible fourth PML patient is a 48-year-old woman who was taking Tysabri along with Avonex, another Biogen Idec MS drug. The possible new case is the third among MS patients who were taking both Tysabri and Avonex. Some doctors have speculated that the two drugs may together sufficiently weaken patients' immune systems to permit the PML infection.
An FDA spokeswoman said in the Globe report that the agency is "in communications" with Biogen Idec "on this case, as well as on the ongoing safety review."
A Biogen spokesman told the Globe, "We're in the middle of our ongoing safety evaluation of Tysabri. We hope to have our findings by the end of the summer. Beyond that we're not commenting on the particulars of our ongoing safety review." Biogen said it would discuss its findings with the FDA.
In February, Biogen Idec and Elan suspended sale of Tysabri and discontinued clinical trials after it was disclosed that one patient had died of PML and another was believed to have it. A third case of the disease was identified in March.
The FDA approved Tysabri in November after reviewing one year of data from planned two-year trials. It also shortened the approval process to six months from the date the companies submitted their application.