Background and objectives: Real-life studies noted that the risk of disease activity in multiple sclerosis (MS) after switching to rituximab (RTX) or ocrelizumab (OCR) may be unequal depending on prior disease-modifying therapy (DMT), with a higher risk associated with fingolimod (FING).
Methods: We performed a retrospective analysis of a structured prospective data collection including all consecutive patients with relapsing MS who were prescribed RTX/OCR in the MS center of Marseille. Cox proportional hazards models were applied to clinical and MRI outcomes.
Results: We included 321 patients with a median (interquartile range [IQR]) follow-up of 3.5 years (1.5-5) after RTX/OCR initiation. At the first RTX/OCR infusion, the mean (SD) age of patients was 37 (10) years, and the median (IQR) disease duration was 8 years (3-15): 68 patients did not receive treatment before RTX/OCR and 108 switched from FING, 47 from low efficacy therapy, and 98 from natalizumab. For statistical analysis, the group "FING" was divided into "short-FING" and "long-FING" groups according to the median value of the group's washout period (27 days). On Cox proportional hazards analysis, for only the "long-FING" group, the risk of relapse within the first 6 months of RTX/OCR was increased as compared with patients without previous DMT (hazard ratio [HR]: 8.78; 95% CI 1.72-44.86; p < 0.01). Previous DMT and washout period duration of FING had no effect on B-cell levels at 6 months. Beyond the first 6 months of RTX/OCR, age <40 years was associated with increased risk of relapse (HR: 3.93; 95% CI 1.30-11.89; p = 0.01), male sex with increased risk of new T2 lesions (HR: 2.26; 95% CI 1.08-4.74; p = 0.03), and EDSS ≥2 with increased risk of disability accumulation (HR: 3.01; 95% CI 1.34-6.74; p < 0.01). Previous DMT had no effect on the effectiveness of RTX/OCR beyond 6 months after initiation.
Discussion: For patients switching from FING to RTX/OCR, the risk of disease reactivation within the first 6 months of treatment was increased as compared with patients with other DMT or no previous DMT only when the washout period exceeded 26 days. Neither FING nor other previous DMT reduced the effectiveness of RTX/OCR beyond the first 6 months of treatment.