Elan Pharmaceuticals and Biogen Idec have said safety data continues to support the treatment of multiple sclerosis (MS) with Tysabri.
The company said more than 21,000 patients were on commercial and clinical Tysabri therapy worldwide as of late December 2007.
Tysabri is a treatment approved for relapsing forms of MS in the United States and relapsing-remitting MS in the European Union.