Using Baseline Paramagnetic Rim Lesion Count as Prognostic and Treatment Biomarkers in Multiple Sclerosis: Jiwon Oh, MD, PhD

WATCH TIME: 6 minutes

“This finding has several clinical and clinical trial implications, particularly for trial design in the future. If we want to enrich clinical trial populations for people more likely to accumulate disability, ‘pearls’ could be considered as a measure to help with this—though, of course, these findings need to be validated.”

Tolebrutinib (Sanofi) is a highly selective, oral Bruton tyrosine kinase (BTK) inhibitor designed to target the BTK enzyme in immune cells, particularly B cells. Unlike other BTK inhibitors, it exhibits strong selectivity, minimizing off-target effects and reducing central nervous system-related adverse events. Its irreversible binding mechanism allows it to permanently attach to the BTK enzyme, potentially offering sustained therapeutic benefits and a lower risk of relapse in multiple sclerosis (MS). Recent research has further highlighted tolebrutinib's potential, particularly in patients with MS who have a higher burden of paramagnetic rim lesions (PRLs).

A post hoc analysis of phase 3 trials, including the HERCULES study (NCT04411641) and GEMINI 1 and 2 trials (NCT04410978; NCT04410991), suggested that the therapy is more effective in patients with higher PRL counts, demonstrating a significant reduction in disability progression.¹ In HERCULES, tolebrutinib reduced the risk of 6-month confirmed disability worsening by 54% in those with at least 4 PRLs, whereas GEMINI participants experienced a 46%-49% risk reduction. These findings, presented by lead author Jiwon Oh, MD, PhD, at the 2025 Americas Committee for Treatment and Research in Multiple Sclerosis (ACTRIMS) Forum, held February 27 to March 1, in West Palm Beach, Florida, underscored PRLs as potential biomarkers for treatment response.

In a follow-up interview with NeurologyLive^®, Oh, medical director at the Barlo Multiple Sclerosis Program, St. Michael’s Hospital, University of Toronto, further elaborated on the prognostic value of baseline PRLs in predicting disability accumulation. She talked about how the study demonstrated that a higher baseline PRL count was associated with increased disability risk and how that tolebrutinib’s effect was more pronounced in patients with greater PRL burdens. Furthermore, Oh emphasized that these findings suggest that PRLs may serve as both prognostic and predictive biomarkers, which could inform clinical trial design and personalized treatment approaches. However, she noted that further validation in additional trials may be needed before PRLs can be integrated into routine clinical decision-making.

Click here for coverage of 2025 ACTRIMS Forum.

REFERENCES
1. Oh J, Fox RJ, Arnold DL, et al. Paramagnetic Rim Lesions as a Prognostic and Predictive Biomarker in the Tolebrutinib Phase 3 Trials for Disability Outcomes. Presented at: 2025 ACTRIMS Forum; February 27-March 1; West Palm Beach, FL. ABSTRACT LB1.1.