Efficacy of Yearly Rituximab Versus Traditional 6-Month Dosing in Relapsing-Remitting MS: Anders Svenningsson, MD, PhD

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"This trial really points to the fact that there are a lot of different trials going on trying to use different doses, and even higher doses, of anti-CD20 therapies. It’s a little concerning regarding safety, because using anti-CD20 therapy is very rewarding, and you don't see so many problems with it in the early years [of the disease]."

The phase 3 RIDOSE-MS trial (NCT03979456) is a randomized, rater-blinded study that compared 500-mg rituximab every 6 months, the typical regimen given, versus every 12 months in patients with relapsing-remitting multiple sclerosis (RRMS). In the study, investigators randomized 104 patients to the 12-month dosing arm and 103 participants to the 6-month arm. The results, presented in a late-breaker at the 2025 European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS) Congress, held September 24-26, in Barcelona, Spain, showed that 12-month dosing of rituximab was effective and noninferior to the standard 6-monthly dosing regimen for RRMS.¹

Presented by lead author Anders Svenningsson, MD, PhD, the trial’s primary outcome was noninferiority of the extended dosing regimen in terms of no evidence of disease activity-3 over the 3-year randomized period. Secondary analyses included biomarker changes and safety assessments, with a focus on reductions in immunoglobulin G (IgG) levels and the development of hypogammaglobulinemia. No new safety signals were observed, but investigators noted that the rate of IgG reduction was approximately 25% slower in patients receiving rituximab every 12 months compared with the 6-month regimen.

In an interview with NeurologyLive^® at the Congress, Svenningsson, professor of neurology in the Department of Clinical Sciences at Karolinska Institutet, discussed the trial’s design and rationale. He explained that the study aimed to determine whether lower doses could maintain efficacy and reduce complications, particularly infections and immune suppression. Svenningsson noted that extending the dosing interval preserved efficacy in preventing relapses and disease activity. Furthermore, he also emphasized the clinical implications for optimizing anti-CD20 therapy, highlighting the importance of balancing treatment efficacy with long-term safety considerations.

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REFERENCES
1. Svenningsson A, Frisell T, Burman J, et al. Rituximab long-term DOSE trial in Multiple Sclerosis – RIDOSE-MS. A phase 3 trial investigating extended dosing regimen of rituximab in relapsing-remitting MS. Presented at ECTRIMS Congress; September 24-26, 2025; Barcelona, Spain. Late-Breaking Abstract O131.