Natalizumab 300 mg every 4 weeks (Q4W) is an effective therapy for relapsing-remitting multiple sclerosis (MS) but is also associated with increased risk of progressive multifocal leukoencephalopathy (PML) in anti–JC virus seropositive patients. Analysis of the TOUCH Prescribing Program safety database showed that natalizumab extended interval dosing (EID; average dosing interval approximately 6 weeks) is associated with lower risk of PML than Q4W dosing. Previous analysis of TYSABRI Observational Program (TOP) data showed no difference in relapse outcomes for patients on Q4W and every-6-week (Q6W) dosing. Comparative disability outcome data in well-matched real-world populations are lacking.
Compare relapse and disability outcomes in propensity-score (PS)–matched TOP patients who switched to Q6W dosing with outcomes in patients who remained on Q4W dosing.
Intentional dosing data collected in TOP as of November 2019 were used to identify patients with ≥1 year of Q4W dosing who remained on Q4W or switched to Q6W dosing. Patients with dosing intervals ≥12 weeks or <3 weeks were excluded. Patients with similar exposures were PS-matched 1:1 with age, sex, Expanded Disability Status Scale score, time from MS onset, exposure duration, and relapse activity as covariates. Between-group comparisons were made for the post-switch follow-up period for Q6W patients and the matching time period for Q4W patients. Adjusted relapse rates (ARRs) were calculated using negative binomial regression with robust standard error estimation. Hazard ratios (HRs) for time to first relapse and 24-week confirmed disability worsening (CDW) were estimated with Kaplan-Meier and Cox methods.
The analysis included 236 matched pairs of Q6W and Q4W patients. Mean (SD) follow-up times for Q6W and Q4W patients were 2.00 (1.30) and 1.89 (1.15) years, respectively. ARRs (0.146 vs 0.139; P=0.796), time to first relapse (HR [95% CI] 1.078 [0.723–1.608]; P=0.711), and time to CDW (HR [95% CI] 0.749 [0.270–2.074]; P=0.578) did not differ significantly for Q6W and Q4W patients.
Relapse and disability outcomes in TOP were similar for PS-matched patients who switched to Q6W or remained on Q4W dosing. These results are consistent with prior matched and unmatched analyses in real-world settings and underscore the need for the ongoing, prospective, randomized efficacy trial of natalizumab Q6W vs Q4W dosing (NOVA, clinicaltrials.gov NCT03689972).
The TOP study was supported by Biogen.