Cladribine tablets in relapsing-remitting multiple sclerosis preferentially target B-cells

Recent studies demonstrate the efficacy of B cell-targeting therapies in managing multiple sclerosis (MS) activity, emphasizing the critical role of B cells in MS pathogenesis. CladB study aimed to quantify the temporal changes in peripheral immune cells and their activity over 96 weeks of Cladribine tablets (CladT) treatment in relapsing-remitting MS (RRMS). Ten participants (3 males, 7 females) had blood samples collected at multiple intervals (Day 0, 1, 5, then weekly for 8 weeks, biweekly for up to 24 weeks, and monthly for up to 96 weeks) for immune cell analysis, compared to a historical alemtuzumab-treated cohort. Paired cerebrospinal fluid (CSF) was also taken for various analyses, alongside clinical and brain imaging assessments. CladT depleted memory B cells, while alemtuzumab rapidly depleted T and B cells. The кFLC index decreased from 164.5 ± 227.1 to 71.3 ± 84.7 at 48 weeks (p = 0.002) and to 64.4 ± 67.3 at 96 weeks (p = 0.01). The IgG index dropped from 1.1 ± 0.5 at baseline to 0.8 ± 0.4 at 48 weeks (p = 0.014) and to 0.8 ± 0.3 at 96 weeks (p = 0.02). CSF CXCL-13 decreased from 88.6 ± 68.4 pg/mL to 39.4 ± 35.2 pg/mL at 48 weeks (p = 0.037) and 19.1 ± 11.7 pg/mL at 96 weeks (p = 0.027). CSF NfL levels were reduced at 48 weeks (p = 0.01). CladT primarily depletes memory B cells and antibody-secreting cell precursors in RRMS, leading to sustained effects on intrathecal antibody production and total IgG, and a reduction in CSF CXCL-13.