With more choices for multiple sclerosis (MS) disease-modifying therapies, data are urgently required to support clinical decisions regarding safe transitioning and sequencing of therapies. With over 7 years of clinical experience, natalizumab has been confirmed as highly effective in reducing MS disease activity. However, natalizumab carries a risk of progressive multifocal leukoencephalopathy (PML). The optimal length of natalizumab washout became the subject of intense consternation and debate. This study suggests a maximum of of 8 weeks but on this subject ProfG has recently posted