Today Genentech announced a 4th case of PML in a person who was JCV positive that was switched from Tysabri to Ocrevus. I learned this from the forum that we use for the International Organization of Multiple Sclerosis Nurses (IOMSN). The thinking among the group is that caution is increasing in switching a JCV+ individual from Tysabri to Ocrevus without at least 3-6 months of washout as all cases have developed after the first dose of Ocrevus and within a couple of months of the last dose of Tysabri. Nurses in NJ, NM and MO all reported today that they had received calls this morning from their Genentech support team alerting to this latest case. I have asked for a link and looked for a link to substantiate this but have not found anything yet. Will post as soon as I do.