Fifteen-year experience with natalizumab in the treatment of multiple sclerosis-a description of 15 clinical cases

Natalizumab, a humanized anti-alpha 4-integrin antibody, is a valuable therapeutic option for relapsing-remitting multiple sclerosis and has been widely used in this indication since 2006. The growing body of data on its high efficacy and safety profile, both from randomised trials and clinical practice, has allowed to identify risk factors for progressive multifocal leukoencephalopathy and to develop a preventive algorithm, which increased the therapeutic safety. Natalizumab also seems relatively safe in pregnant women as there is no indication in the available literature suggesting that exposure to this drug has a significant impact on pregnancy outcomes. However, adequate and well-controlled studies are still lacking and natalizumab should only be used in pregnancy if clearly needed. The mechanism of action of natalizumab also proved successful during the COVID-19 pandemic. Most patients receiving this therapy experienced only mild infection and developed normal vaccine-induced immunity after immunisation. We present a description of 15 patients with relapsing-remitting multiple sclerosis treated with natalizumab in 15 different centres throughout Poland. The drug was included both due to first-line treatment failure and in cases of rapidly progressing, severe form of multiple sclerosis. The patients differed in terms of disease duration, the length of natalizumab therapy, and JCV serological status. The described cases include patients from the natalizumab registration trial, women who became pregnant while on the therapy, and patients who developed COVID-19. The presented case reports summarise the experience to date with the use of natalizumab in the treatment of relapsing-remitting multiple sclerosis in Poland.