Biogen and Elan had voluntarily removed Tysabri from the US market and all ongoing clinical trials following reports of three patients developing a rare and potentially fatal brain disease called progressive multifocal leukoencephalopathy (PML).
Now that the hold on clinical trial dosing of Tysabri (natalizumab) in multiple sclerosis (MS) has been removed, the companies expect to begin a multi-center safety extension study of the drug as a monotherapy. Patients who previously participated in the phase III MS program are eligible for entry.
The companies completed a comprehensive safety evaluation of more than 3,000 Tysabri patients in collaboration with leading experts in PML and MS. The results of the safety evaluation yielded no new confirmed cases of PML beyond those three previously reported.
The FDA is due to make a decision on whether the drug can re-enter the market by March 2006.