Biogen, Elan report cases of brain disease

Two multiple-sclerosis patients treated with Biogen Idec Inc.'s drug Tysabri contracted a potentially deadly brain infection. The news casts a cloud over the revival of the medicine, which was already withdrawn once over safety concerns. Biogen said it had no plans to recall the drug again or restrict its use. The company said that the two patients who contracted the ailment, progressive multifocal leukoencephalopathy, or PML, are alive.