Efficacy and safety of extended-interval dosing of natalizumab in multiple sclerosis: a systematic review and meta-analysis with subgroup evaluation.

BACKGROUND

Natalizumab is effective for relapsing-remitting multiple sclerosis (RRMS) but increases the risk of progressive multifocal leukoencephalopathy (PML). Extended-interval dosing (EID) may lessen this risk by reducing drug exposure, though its efficacy and safety compared with standard-interval dosing (SID) remain unclear. This review and meta-analysis evaluates both regimens across clinical and MRI outcomes.

METHODS

Following PRISMA guidelines, we systematically searched PubMed, Scopus, Web of Science, Cochrane Library, and ScienceDirect from inception to July 2025. Eligible studies compared extended- (5-12 weeks) and standard-interval (4 weeks) natalizumab dosing in MS. Meta-analyses used random- or fixed-effects models with results as RR or MD based on heterogeneity (I²).

RESULTS

Twenty-five studies were included. Analysis showed no significant differences between EID and SID in disability progression (MD -0.09, 95% CI: -0.46 to 0.29), or the risk of new T2 lesions (RR 1.24, 95% CI: 0.96 to 1.61). For PML incidence (RR 1.03, 95% CI: 0.29-3.60), the analysis was severely underpowered due to rare events; the wide confidence interval precludes any firm conclusion about comparative safety. However, EID was associated with a significantly higher risk of gadolinium-enhancing lesions (RR 1.35, 95% CI: 1.03-1.77). EID was associated with a borderline reduction in the risk of clinical relapse (RR 0.91, 95% CI: 0.83 to 1.00), but this finding is likely influenced by selection bias and should be considered hypothesis-generating rather than confirmatory. Subgroup analysis suggested a possible difference between intervals (P = 0.0323 for T2 lesions), but this finding is based on very sparse data, with only one subgroup (Q5-8 W) containing multiple studies and all other subgroups relying on single studies. Therefore, no definitive conclusion about optimal interval length can be drawn; the result is hypothesis-generating only.

CONCLUSION

Extended-interval dosing of natalizumab shows efficacy and safety comparable to standard dosing. Although relapse reduction was noted, this may reflect selection bias. Shorter EID intervals (5-8 weeks) appear to maintain better radiologic control, supporting EID up to 6-8 weeks as a viable option pending long-term and biomarker-guided validation.