Overviewing Phase 3 ARTIOS Findings on Ofatumumab

At the 2025 European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS) Congress, held September 24-26, in Barcelona, Spain, new findings on ofatumumab (Kesimpta; Novartis) drew significant attention for their implications in relapsing multiple sclerosis (MS). Among them were results from the ARTIOS trial, which evaluated patients switching from fingolimod or fumarate-based therapies after breakthrough disease, showing striking reductions in both relapses and MRI activity. In addition, long-term extension data reinforced the durability of ofatumumab’s efficacy and safety profile, underscoring its role as a central B-cell–depleting therapy in the MS landscape.

In this NeurologyLive^® Special Report mini-series, Riley Bove, MD, an associate professor of neurology at the University of California, San Francisco, breaks down the latest evidence and shares key takeaways for clinical practice. Across four short episodes, Bove explores how ofatumumab differs from other therapies, interprets the new ARTIOS results, reflects on its evolving use since approval, and looks ahead to the questions still shaping MS treatment research.

In episode 2, Bove provides a detailed overview of the ARTIOS phase 3b trial, as well as some of the major findings presented at ECTRIMS 2025. She reviews the remarkably low adjusted annualized relapse rate of 0.06 and the near-complete suppression of MRI activity at 96 weeks. Key insights include reductions in both gadolinium-enhancing and new T2 lesions, supporting ofatumumab’s effectiveness in switch scenarios.

Transcript edited for clarity.

Riley Bove, MD: The ARTIOS trial was essentially a 96-week, phase 3b, open-label study. “Open-label” means that participants knew they were being switched to a new therapy. The study included adults with MS who were previously on fingolimod or fumarate-based medications but had recent MRI evidence of new inflammatory activity—T2 lesions or gadolinium-enhancing lesions—or recent clinical relapses. These individuals were switched over to ofatumumab for the 96-week study period.

The outcomes we looked at included the annualized relapse rate, or ARR, which was our primary endpoint. The adjusted ARR was exceptionally low at 0.06 relapses per year, which is very impressive—almost a “floor effect.” We also looked at MRI outcomes, which are important because patients can develop new lesions in the brain or spinal cord without showing obvious clinical relapses.

In terms of MRI activity, we saw dramatic reductions in both gadolinium-enhancing lesions and new T2 lesions. By week 96, there was a 98.1% reduction in gadolinium-enhancing lesions, and the adjusted number of new T2 lesions was very low at 0.07. These were excellent outcomes overall, and importantly, no new safety signals were observed during the trial.