Abstract Background Inflammatory bowel disease (IBD) is a complex disease characterized by the dysregulation of multiple factors, including host immunity. The intestinal activation of T cells showing cytotoxic activity and pro-inflammatory cytokine production is one of the key factors in its pathology. Therefore, targeting pro-inflammatory leukocytes from the circulation and in the inflammatory site is a reasonable therapeutic goal. CCR9 is the main activator of gut-tropism in the lymphocytes and responsible for the activation of migratory responses in lymphocytes into the lamina propria. SBR1 is a humanized IgG1 anti-CCR9 mAb showing high-affinity and specific binding towards CCR9+ cells. Displaying effector functions such as Antibody-Dependent Cellular Cytotoxicity (ADCC) and Antibody-Dependent Cellular Phagocytosis (ADCP), SRB1 shows specific depletion of infiltrating and circulating CCR9+ cells in vivo and restores the immune homeostasis in patient samples of Crohn’s Disease and Ulcerative Colitis. Methods Matching blood and 5 mm gut explants were obtained from IBD patients, then they were cultured for 16h with SRB1 and subsequently, CCR9+ cells were characterized by flow cytometry. The culture supernatants from these explants as well as blood samples from the same patients were analyzed for pro-inflammatory cytokine production by Multiplex cytokine immune assay. Finally, in non-human primates (Macaca fascicularis) CCR9 cell depletion was determined by flow cytometric assays at doses of 8, 15 y 25 mg/kg. Results We showed that CCR9 is highly expressed in intestine samples from IBD patients, especially in T cells, but also in other cell types including dendritic cells, macrophages and neutrophils. Treatment with SRB1 was able to effectively deplete CCR9+ cells, specifically T CD4+ CCR9+ and CCR9+ memory T cells from blood and intestinal samples from IBD patients. This depletion also reduced the pro-inflammatory cytokine levels in the culture media. Finally, SRB1 also showed efficacy depleting CCR9 in non-human primates (Macaca fascicularis) at different doses without showing any secondary adverse effects. All these data suggest a potential therapeutic potential of the antibody in the pathogenesis of IBD patients. Conclusion SRB1 delivers potent blood and tissue depletion of CCR9 expressing cells ex vivo and in vivo and restores the immune homeostasis in patients’ samples of Crohn’s Disease and Ulcerative Colitis. These data demonstrate the therapeutic potential of SRB1 (anti-CCR9 mAb) a novel therapeutic approach for Inflammatory Bowel Diseases including CD and UC.
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