Effectiveness of 6-week dosing of Natalizumab versus continued 4-week treatment for Multiple Sclerosis: An observational registry-based study.

Background: Multiple sclerosis (MS) impacts quality of life. Every-4-week (Q4W) regimen of natalizumab (NTZ) is approved for relapsing-remitting multiple sclerosis (RRMS) but increases progressive multifocal leukoencephalopathy (PML) risk. This study aimed to assess the impact of switching to an every-6-week (Q6W) dosing of NTZ in RRMS patients previously treated with Q4W dosing for ≥12 months.

Methods: This observational, registry-based, two-armed, retrospective comparative study included 243 patients (69 males and 174 females; mean age=35.7 ± 8.8 years) from the Kuwait National Registry between January 2018 and June 2023. All patients initially received NTZ Q4W. After one-year, 202 patients were switched to Q6W, while 41 remained on Q4W. Outcome parameters included patients free from clinical relapse, annualized relapse rate (ARR), expanded disability status scale (EDSS), confirmed disability worsening (CDW), no evidence of disease activity (NEDA), magnetic resonance imaging findings, and adverse events (AE). Kaplan-Meier survival curves depicted clinical endpoints for both groups.

Results: Relapse proportion, ARR, EDSS, and new/enlarged T2 and gadolinium lesions significantly reduced after initiating NTZ (p < 0.05). CDW occurred in 7.4 % of patients and NEDA in 86.2 %. No significant difference (p > 0.05) was observed between the Q4W and Q6W groups for any parameters. AEs were reported in 13 patients (p = 0.88). Kaplan-Meier analysis demonstrated no significant difference (p > 0.05) in the mean survival times without relapse, AEs, new T2 lesions, and without disability progression between groups.

Conclusions: Both Q4W and Q6W NTZ regimens provided comparable safety and effectiveness in RRMS patients, effectively preventing relapses, AEs, disability progression, and occurrence of enlarged/new T2 lesions. In addition, no patient developed PML.