119 Long-term effectiveness of natalizumab for RRMS: UK and global interim results from TYSABRI observational program

IntroductionThe TYSABRI Observational Program (TOP) is an ongoing observational study of natalizumab treatment in relapsing-remitting multiple sclerosis (RRMS) patients. Country-specific data on relapse and disability outcomes, alongside global data, can provide information on natalizumab’s effectiveness in local practice.MethodsAnnualised relapse rate (ARR) was analysed in TOP UK (n=134) and global (N=6320) cohorts using data from July 2007 to November 2020. A subgroup analysis assessed ARR in patients with one prior disease modifying therapy (DMT) in the UK (n=64) and global (n=2795) cohorts. Cumulative probabilities of 24-week confirmed disability worsening and improvement will be presented.ResultsARR decreased in UK patients from 2.21 in the year before initiation to 0.16 on natalizumab (P<0.0001), consistent with a global decrease from 2.00 to 0.18 (P<0.0001). In patients with one prior DMT, ARR decreased in UK patients from 2.13 in the year before initiation to 0.15 on natalizumab (P<0.0001), similar to the global decrease from 2.03 to 0.16 (P<0.0001).ConclusionsThe reduction in ARR on natalizumab was similar in the TOP UK and global cohorts, including in the subset of patients with one prior DMT. These findings support the real-world effectiveness of natalizumab.Support.Biogen. Disclosures: Included on the poster. jean.vonsy@biogen.com