A Study Utilising Data From European Union (EU) National Multiple Sclerosis (MS) Registries to Assess the Incidence of Anti-Natalizumab Antibody Among Participants Who Receive Subcutaneous Administration of Natalizumab for Treatment of Relapsing-remitting Multiple Sclerosis (RRMS)

The primary objective of this study is to estimate the incidence of Anti-Natalizumab Antibodies (ANAs) in the cohort of natalizumab-naïve and other MS monoclonal antibody (mAb)-naive participants who start receiving natalizumab subcutaneous (SC) injections. The secondary objectives of this study are to estimate the proportion of participants detected with ANAs when switched from natalizumab intravenous (IV) to natalizumab SC (natalizumab-experienced cohort); to evaluate serious adverse events (SAEs), including injection reactions and hypersensitivity reactions, by ANA status and to assess the proportion of participants who had MS relapse, by ANA status.