Efficacy and Safety of Natalizumab in Multiple Sclerosis: Interim Observational Program Results from an Australian Cohort.

Background: The Tysabri Observational Program (TOP) evaluates long-term safety and impact on disability and disease progression of natalizumab. Here we describe the safety and efficacy of natalizumab in Australian participants compared with the global cohort.

Methods: In this ongoing, open-label, multinational, prospective, observational study, patients receive natalizumab 300 mg intravenously every 4 weeks. Primary endpoint: incidence/type of serious adverse events (SAEs). Secondary endpoints include incidence of relapses and change in EDSS score.

Results: Data from 5770 patients (179 from the Australian cohort) that enrolled between July 2007 and May 2015 were analysed. Mean baseline EDSS was 3.5 (SD 1.62) and 3.8 (SD 1.86), in the global and Australian cohorts, respectively, and 12.1% and 19.6% patients had baseline EDSS ⩾6. In the global and Australian cohorts, respectively, 10.8% and 20.1% patients experienced ⩾1 SAE; the incidence of treatment-related SAEs was 3.8% and 4.5%. After 6 years of therapy, mean change from baseline in EDSS score was +0.5 in the Australian group and 0.0 in the global cohort. Annualised relapse rate (ARR) for the global group was 1.99 pre-treatment and 0.23 post-treatment; ARR pre- and posttreatment in Australian patients was 1.70 and 0.21. At 6 years, probability of confirmed EDSS progression was 23.9% and 31.85%, and confirmed EDSS improvement 33.08% and 40.47% in the Global and Australian cohorts respectively.

Conclusions: In the Australian cohort of patients treated with natalizumab, we observed a low incidence of treatment-related AEs, low relapse probability, and sustained clinical efficacy, comparable to the global cohort.