B-lymphocyte-guided retreatment contributes to establish good effectiveness and safety profile in MS patients treated with rituximab.

Background: Rituximab is extensively used for multiple sclerosis (MS) treatment. However, the best dosage remains to be established. It has been proposed that retreatment could be guided by B lymphocyte (BL) percentages.

Objective: To establish the best BL value for retreatment with rituximab in MS and to confirm the safety and efficacy of this approach.

Methods: A prospective study was done with an exploratory cohort and a confirmatory cohort of MS patients treated with rituximab between 2017 and 2021. The first one comprised 10 MS patients with BL assessed every 3 months after rituximab infusion and retreatment done when BL values were ≥0.5%. The confirmatory cohort included 41 MS patients (41.5% women, 87.8% with secondary progressive MS, median age = 46.3 (interquartile range: 41.3-52.1) years, disease duration = 14.1 (9-19.6) years, EDSS score = 5.5 (4.0-6.5)). The confirmatory cohort was treated with rituximab following the pattern established in the exploratory cohort.

Results: In the exploratory cohort, ≥0.2% BL was established as the best value for retreatment because in most cases, a substantial increase of BL counts was preceded by initial values of 0.2-0.3%. In the confirmatory cohort, rituximab reduced the annualized relapse rate (ARR 0.56 vs. 0.125, p < 0.001), proportion of patients with appearance of new/enlarged T2 lesions (63.4% vs. 12.2%, p < 0.001), gadolinium-enhancing lesions (39% vs. 0%, p < 0.001), and confirmed disability progression (55% vs. 27.5%, p = 0.037). There were 22 patients (53.7%) who achieved NEDA-3. No patients had severe infections, and 10.7% cases had reduced IgG levels.

Conclusion: Rituximab treatment guided by BL showed high effectiveness and a good safety profile for MS patients after one year of treatment.