On February 28, 2005, Biogen Idec and Elan announced that they voluntarily suspended Tysabri from the US market and all ongoing clinical trials based on reports of progressive multifocal leukoencephalopathy (PML), a rare and potentially fatal, demyelinating disease of the central nervous system. Three confirmed cases of PML were previously reported, two of which were fatal.
The companies have already submitted a supplemental Biologics License Application for Tysabri to the FDA for the treatment of MS. The companies also recently submitted a similar application to the European Medicines Agency.
More than 1,500 Crohn’s disease and rheumatoid arthritis patients from clinical trials were eligible for the safety evaluation. A total of 88% of these patients participated in the safety evaluation. In total, 98% of the patients participating in the evaluation had a neurological exam by a consultant neurologist and an MRI exam.