Oral Treatment with BT-11 Ameliorates Inflammatory Bowel Disease by Enhancing Regulatory T Cell Responses in the Gut

Inflammatory bowel disease (IBD) is an expanding autoimmune disease afflicting millions that remains difficult to treat due to the accumulation of multiple immunological changes. BT-11 is an investigational new drug for IBD that is orally active, gut restricted, and targets the lanthionine synthetase C-like 2 immunometabolic pathway. CD25⁺ FOXP3⁺ CD4⁺ T cells are increased locally within the colon of BT-11–treated mice in Citrobacter rodentium and IL-10^−/− mouse models of colitis. The maintained efficacy of BT-11 in the absence of IL-10 combined with the loss of efficacy when direct cell–cell interactions are prevented suggest that the regulatory T cell (Treg)–related elements of suppression are cell contact–mediated. When PD-1 is inhibited, both in vitro and in vivo, the efficacy of BT-11 is reduced, validating this assertion. The depletion of CD25⁺ cells in vivo abrogated the retention of therapeutic efficacy postdiscontinuation of treatment, indicating that Tregs are implicated in the maintenance of tolerance mediated by BT-11. Furthermore, the involvement of CD25 suggested a role of BT-11 in IL-2 signaling. Cotreatment with BT-11 and IL-2 greatly enhances the differentiation of CD25⁺ FOXP3⁺ cells from naive CD4⁺ T cells relative to either alone. BT-11 enhances phosphorylation of STAT5, providing a direct linkage to the regulation of FOXP3 transcription. Notably, when STAT5 is inhibited, the effects of BT-11 on the differentiation of Tregs are blocked. BT-11 effectively enhances the IL-2/STAT5 signaling axis to induce the differentiation and stability of CD25⁺ FOXP3⁺ cells in the gastrointestinal mucosa to support immunoregulation and immunological tolerance in IBD.

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