Rituximab Treatment of Highly Active Multiple Sclerosis (MS) After Natalizumab-Related Progressive Multifocal Leukoencephalopathy (PML) (P6.166)

to report on a young woman affected by multiple sclerosis with a severe disease reactivation after the natalizumab withdrawal due to PML. Active MS was subsequently treated with rituximab. Background: natalizumab is highly effective in MS but is linked to the risk of PML, a demyelinating infection of the central nervous system (CNS) caused by the polyoma virus JC. Natalizumab withdrawal is mandatory in the occurrence of PML but harsh MS reactivation can occur and an immunomodulant therapy must be restored. Design-methods: PML occurred in October 2014 after 48 natalizumab infusions; in December, after immuno-reconstitution, the patient had a clinical MS reactivation with several new gadolinium enhancing MRI lesions in the brain and spinal cord; the EDSS worsened from four (at baseline) to seven. After one month on fingolimod, a new severe relapse occurred (EDSS 8.5 - new MRI active lesions); fingolimod was stopped in February 2015. Rituximab was introduced in May 2015 and three infusions (two in May 2015, one in September 2015, according to the lymphocyte CD19 count) were administered; a better clinical condition was obtained until October 2015 (EDSS 5.5). Results: rituximab led to the clinical MS remission and MRI stability without the PML relapse. Conclusions: Therapy with rituximab might be an option in treatment of MS patients with severe active MS disease, after Natalizumb - PML. To our knowledge, this is the first described case with a one-year follow-up. Disclosure: Dr. Cordioli has received personal compensation for activities with Genzyme and Biogen Idec. Dr. De Rossi has nothing to disclose. Dr. Rasia has nothing to disclose. Dr. Santuccio has received personal compensation from Novartis and Teva for activities as a speaker. Dr. Ruggero Capra has nothing to disclose.