Effect of the sphingosine-1-phosphate receptor modulator ozanimod on leukocyte subtypes in relapsing MS

OBJECTIVE: To better understand ozanimod's mechanism of action (MOA), we conducted exploratory analyses from a phase 1 study to characterize ozanimod's effect on circulating leukocyte subsets in patients with relapsing multiple sclerosis. METHODS: An open-label pharmacodynamic study randomized patients to oral ozanimod hydrochloride (HCl) 0.5 (n = 13) or 1 mg/d (n = 11) for ∼12 weeks (including 7-day dose escalation). Circulating leukocyte subsets were quantified using flow cytometry (days 28, 56, and 85) and epigenetic cell counting (days 2, 5, 28, 56, and 85) and compared with baseline (day 1) using descriptive statistics. RESULTS: Ozanimod caused dose-dependent reductions in absolute lymphocyte counts. Observed by both methodologies, circulating CD19(+) B- and CD3(+) T-cell counts were reduced by >50% with ozanimod HCl 0.5 mg and >75% with 1 mg at day 85. Based on flow cytometry, ozanimod HCl 1 mg showed greater decreases in CD4(+) than CD8(+) T cells, greater decreases in both CD4(+) and CD8(+) central memory vs effector memory T cells, and reductions in mean CD4(+) and CD8(+) naive T cells by ≥90% at day 85. In the flow cytometry analysis, changes in monocytes, natural killer, and natural killer T cells were minimal. Using epigenetic cell counting, greater reductions for Th17 than T regulatory cells were determined. CONCLUSION: Ozanimod induced dose-dependent reductions in circulating B- and T-cell counts and differential effects on naive and memory CD4(+) and CD8(+) T cells and CD19(+) B cells. Data characterized with both a novel epigenetic cell-counting method and flow cytometry support ozanimod's MOA. CLINICAL TRIAL REGISTRATION: clinicaltrials.gov NCT02797015.