Ocrelizumab depletes T-lymphocytes more than rituximab in multiple sclerosis

Background: We aim to directly compare changes in lymphocyte subpopulations between chimeric (rituximab) and humanised (ocrelizumab) anti-CD20 antibodies in multiple sclerosis (MS). Methods: In this retrospective analysis of prospectively collected data, we included 88 patients with MS, treated with rituximab (n=50) or ocrelizumab (n=38). We used flow cytometry in the peripheral blood to count total lymphocytes and lymphocytes expressing different phenotypic markers (CD4, CD8, CD19, CD20, CD4/CD8 ratio), before treatment and after 1, 3 and 6 months. Results: On linear mixed effect regression models, after 1, 3 and 6 months, patients treated with rituximab and with ocrelizumab were similar in total lymphocyte count, CD19 lymphocytes, CD20 lymphocytes and CD4/CD8 ratio. However, patients treated with ocrelizumab presented with lower CD4 T lymphocytes and CD8 T lymphocytes after 1, 3 and 6 months (all p<0.05). No between-treatment difference in EDSS progression was found. Discussion: B-cell levels in the peripheral blood were equally decreased by rituximab and ocrelizumab. On the contrary, CD4 and CD8 T lymphocyte reduction was more pronounced in ocrelizumab, when compared with rituximab, suggesting a broader immunomodulatory effect for the humanised antibody to be confirmed and correlated with clinical efficacy in the long term.

Automated summary

Both rituximab and ocrelizumab similarly decrease B-cell levels in peripheral blood of multiple sclerosis patients, but ocrelizumab shows a more pronounced reduction in CD4 and CD8 T lymphocytes. The two antibodies have comparable effects on reducing lymphocyte count, and the broader immunomodulatory effect of ocrelizumab needs to be confirmed and correlated with long-term clinical efficacy.