Relationship between baseline treatment history and post baseline relapses and serious adverse events in natalizumab-treated patients with multiple sclerosis

The purpose of this analysis is to evaluate associations between baseline treatment history, post-baseline annualized relapse rate (ARR) and safety (serious adverse events (SAEs)) in patients treated with natalizumab in the TOP study, which is an ongoing, open-label, multicenter, observational study being conducted in Europe, Australia, and Canada that began recruiting patients with relapsing multiple sclerosis (MS) in July 2007.
TOP will enroll >3000 patients who will be followed for 5 years. As of December 2010, 2943 patients from 15 countries were enrolled in the TOP study.

Regardless of treatment history, patients treated with natalizumab had significant reductions in mean ARR. Mean ARRs on natalizumab treatment were lowest in patients who were therapy naive and highest in patients who were previously treated with Immunosuppressive (IS) therapy, suggesting a potential benefit of treatment with natalizumab early in the course of disease. Disability, as assessed by Expanded Disability Status Scale (EDSS), improved slightly from baseline and remained stable over time. Although there were no significant differences in the incidence of SAEs by treatment history, SAEs seemed to occur more frequently in patients previously exposed to IS therapy.
These data are consistent with the current knowledge that Progressive multifocal leukoencephalopathy (PML) risk increases with treatment duration and prior IS use. As TOP and other observational registries of natalizumab-treated patients progress, they will continue to generate valuable data on the long-term efficacy and safety profile of natalizumab in a clinical practice setting.

No relevant conflicts of interest declared.