Oral FPR2/ALX modulators tune myeloid cell activity to ameliorate mucosal inflammation in inflammatory bowel disease

Current treatments of inflammatory bowel disease (IBD) largely depend on anti-inflammatory and immunosuppressive strategies with unacceptable efficacy and adverse events. Resolution or repair agents to treat IBD are not available but potential targets like formyl peptide receptor 2 (FPR2/ALX) may fill the gap. In this study we evaluated the therapeutic effects of two small molecule FPR2/ALX modulators (agonist Quin-C1 and antagonist Quin-C7) against IBD. We first analyzed the cryo-electron microscopy structure of the Quin-C1-FPR2 in complex with heterotrimeric G_i to reveal the structural basis for ligand recognition and FPR2 activation. We then established dextran sulfate sodium (DSS)-induced colitis model in both normal and myeloid depletion mice. We showed that oral administration of Quin-C1 for 7 days ameliorated DSS-induced colitis evidenced by alleviated disease activity indexes, reduced colonic histopathological scores, and corrected cytokine disorders. Meanwhile, we found that oral administration of FPR2/ALX antagonist Quin-C7 exerted therapeutic actions similar to those of Quin-C1. In terms of symptomatic improvements, the ED₅₀ values of Quin-C1 and Quin-C7 were 1.3660 mg/kg and 2.2110 mg/kg, respectively. The underlying mechanisms involved ERK- or ERK/JNK-mediated myeloid cell regulation that limited the development of colitis and inflammation. This is the first demonstration of anti-colitis property caused by synthetic small molecule FPR2/ALX modulators, implying that FPR2/ALX modulation rather than agonism alone ameliorates IBD.