Challenges of switching towards anti-CD20 monoclonal antibodies in RR-MS: A monocentric study

Background: Anti-CD20 monoclonal antibodies (mAb) have demonstrated their drastic efficacy in the treatment of active relapsing-remitting multiple sclerosis (RR-MS). This study investigates the management of their initiation after another disease modifying therapy (DMT). The objective of this study was to assess the frequency and the risk factors of relapses during the wash-out period (WP) between cessation of last DMT and initiation of antiCD20 mAb in RR-MS. Methods: All non-naive RR-MS patients who initiated a treatment with Rituximab or Ocrelizumab between 2016 and 2019 have been included in this retrospective monocentric study. Univariate and multivariate analysis were conducted to evaluate risk factors of relapses during the WP. Results: 73 patients (mean age 35.3 years, standard deviation (SD): 8.7 years) were included, with a mean number of 3.1 (SD: 1.3) previous DMTs. The DMT most frequently received before the switch was Fingolimod (Fg, 31 patients, 42.5%). 20 patients (27.4%) experienced relapses during the WP. Risk factors were previous treatment by Fg (p = 0.001) and WP duration (p = 0.032). Among patients switching from Fg, the probability of experiencing a relapse was 35% after 1 month of wash-out. Conclusion: This study suggests to shorten the WP duration when switching towards anti-CD20 mAb, especially after Fg, to avoid relapses.