Ocrelizumab is the first drug approved as disease modifying treatment for primary progressive (PP) multiple sclerosis (MS). As a humanized monoclonal antibody targeting CD20 cells, it is widely known that ocrelizumab treatment results in B cells depletion, but less is known about the effects of this drug in other blood leukocyte subsets of PPMS patients.
To explore the changes induced by ocrelizumab in blood immune cells of PPMS patients to further understand their effects in the abnormal inflammatory response.
Multi-centre prospective longitudinal study including fifty‐three PPMS patients who initiated ocrelizumab treatment. Effector, memory, and regulatory cells were analyzed by flow cytometry at baseline and after 6 months of treatment. To assess differences between baseline and after 6 months, Wilcoxon matched paired tests were used and p values were corrected using Bonferroni test.
Ocrelizumab decreased numbers of naïve and memory B cells (p<0.0001) and those of B cells producing interleukin (IL)-6, IL-10, granulocyte-macrophage colony-stimulating factor and tumor necrosis factor-alpha (p<0.0001 in all cases). A reduction of CD20+ T cell numbers (p=0.02) and percentages (p<0.0001) was also observed. We also detected a clear remodelation of the T cell compartment characterized by relative increases of the naïve/effector ratio in CD4+ (p=0.002) and CD8+ (p=0.002) T cells, and relative decreases of CD4+ (p=0.03) and CD8+ (p=0.004) T cells producing interferon-gamma. Total monocyte numbers increased (p=0.002), with no changes in those producing inflammatory cytokines. All these changes resulted in a reduction of serum neurofilament light chain (sNfL) levels (p=0.009).
Effector B cell depletion by ocrelizumab treatment induces changes in the T cell response of PPMS patients towards a low inflammatory profile. This resulted in a decrease of sNfL levels.