FDA: Tysabri offers more benefits than risks

The Food and Drug Administration on Friday issued a safety statement to alert medical professionals and the public to the risk of progressive multifocal leukoencephalopathy (PML) in patients who use Tysabri.

Tysabri was approved by the FDA in Nov 2004 for the treatment of relapsing forms of multiple sclerosis or MS and also moderately to severely active Crohn's disease.

The safety alert came after the health agency received a total of 31 reports of confirmed cases of PML as of Jan 12, 2020.

The risk of PML linked to Tysabri wasn't new to the FDA.  The agency was notified of a few severe cases of PML including one fatal case and one additional case of severely disabling PML in MS patients receiving the drug and one fatal case in one patient with Crohn's disease a couple of years after the approval of this medication for marketing in the U.S.

These cases once prompted the FDA to request Biogen-IDEN, the drug maker, to suspend its marketing of Tysabri and ongoing clinical trials on the drug.  The FDA lifted the clinical hold on the trials for patients with multiple sclerosis in 2006.

More cases were reported to the FDA over the years.  By September 8 2009, the agency had received 13 cases of Tysabri related PML in MS patients.  At this time, the FDA had known that patients who received 12 to 35 infusions are at higher risk of developing PML, but still believed the risk isn't big enough to request the drug manufacturer to put a warning on the label.  Of 10,000 patients who received at least 24 infusions, 13 got MPL, according to the FDA.

Because of the increased number of PML cases, the FDA now requires that new safety information be included in the Tysabri drug label and Patient Medication Guide.

By David Liu