Aim: Anti-CD20 monoclonal antibodies and fumarates are common multiple sclerosis (MS) disease-modifying therapies (DMTs). Data on switching from anti-CD20s to other DMTs are limited. This retrospective, observational study of the US Komodo Health Sentinel claims database aimed to evaluate a de-escalation strategy in a real-world cohort, comparing clinical characteristics, relapses, healthcare encounters (HCEs) and healthcare costs (HCCs) between patients aged ≥18 years with stable MS who switched from anti-CD20s to fumarates ('Switchers') versus patients who stayed on anti-CD20s ('Stayers'). Materials &

Methods: Patients with MS (diagnosed 1 January 2015-31 August 2022) were propensity score matched 5:1 (Stayers:Switchers) and followed from index to end of study; end of insurance eligibility; >45-day gap in index DMT; or DMT switch. Primary outcomes were clinical characteristics and claims-based annualized relapse rate (ARR). Rates of HCEs and HCCs were estimated.

Results: Baseline characteristics were well balanced between cohorts (Stayers, n = 540; Switchers, n = 108). Mean (SD) duration of post-index follow-up was 341.4 (250.0) days for both cohorts. Mean (SD) ARR was 0.08 (0.41; Stayers) versus 0.14 (0.5; Switchers; p = 0.3). Twenty-one Stayers (3.9%) and 1 Switcher (0.9%) were hospitalized for infections, with mean stays of 9.9 and 1 day, respectively. Mean annualized all-cause HCEs were similar between cohorts; annualized inpatient infection-related HCEs were higher for Stayers versus Switchers (mean difference: -0.05; p = 0.005). Annualized all-cause HCCs were similar between cohorts; Switchers had lower annualized infection-related HCCs overall (mean difference: -$2412; p = 0.002) and in the inpatient setting (mean difference: -$2325; p = 0.002).

Conclusion: After 1 year, no significant differences in ARR emerged between cohorts. Switchers experienced lower inpatient infection-related HCEs, shorter inpatient infection-related hospital stays and lower overall infection-related HCCs.