A Novel Approach to Restore Epithelial Barrier Homeostasis to Treat Inflammatory Bowel Disease

总结 肠道屏障功能在肠道和全身性疾病中受损，包括感染性疾病。 小肠结肠炎、食物过敏、乳糜泻、移植物抗宿主病（GvHD）和炎性 肠道疾病（IBD）。Thursday Therapeutics的联合创始人发现， 肌球蛋白轻链激酶（MLCK）在屏障调节中的作用，并证明靶向肠 上皮MLCK抑制限制了实验性IBD和GvHD。不幸的是，严重的毒性 与上皮和其它组织中的屏障非依赖性MLCK功能相关，例如，光滑 肌肉，排除MLCK酶活性的治疗靶向。我们最近报道 （Graham等人，Nature Medicine，2019），一种特定的MLCK剪接变体MLCK 1是 屏障调节，并依赖于免疫球蛋白-细胞粘附介导的相互作用 分子结构域3（IgCAM 3）。我们解析了IgCAM 3晶体结构，确定了药物结合 pocket），并筛选了约140，000个药物样分子的文库。我们的工具 化合物，Divertin，结合IgCAM 3，阻止马槟榔碱诱导的MLCK 1募集，肌球蛋白II 调节轻链磷酸化和屏障功能障碍。关键的是， MLCK酶功能、上皮伤口愈合或平滑肌收缩，以及体内 毒性研究未能确定不良影响。Divertin预防TNF诱导的急性屏障 体内（小鼠）和离体（人肠活检）损失，并恢复免疫介导的 体内屏障丧失（IL-10敲除小鼠）。最后，Divertin延迟了发作， 实验性免疫介导（T细胞转移）IBD的进展，如屏障所示 保存和恢复，减少粘膜免疫激活，并提高生存。中 在第一阶段SBIR中，我们通过发现具有改进的 活动命中化合物是通过严格的排序筛选漏斗发现的， 鉴定具有合适的MLCK 1结合亲和力、在保存和恢复中的功效的化合物 上皮屏障功能和酶抑制活性的缺乏。在第二阶段的提案中， 这些命中化合物将用迭代结构活性关系研究来优化， 在IBD的小鼠模型中测试毒性和功效。这项工作将有助于 研究一流和一流的障碍恢复治疗，以管理 胃肠道和全身性疾病。

SUMMARY Intestinal barrier function is compromised in enteric and systemic diseases, including infectious enterocolitis, food allergy, celiac disease, graft versus host disease (GvHD), and inflammatory bowel disease (IBD). The co-founders of Thelium Therapeutics discovered the central role of myosin light chain kinase (MLCK) in barrier regulation and demonstrated that targeted intestinal epithelial MLCK inhibition limits experimental IBD and GvHD. Unfortunately, severe toxicities associated with barrier-independent MLCK functions in epithelia and other tissues, e.g., smooth muscle, preclude therapeutic targeting of MLCK enzymatic activity. We recently reported (Graham et al., Nature Medicine, 2019) that a specific MLCK splice variant, MLCK1, is central to barrier regulation and depends on interactions mediated by immunoglobulin-cell adhesion molecule domain 3 (IgCAM3). We solved the IgCAM3 crystal structure, identified a drug binding pocket unique to IgCAM3, and screened a library of ~140,000 drug-like molecules. Our tool compound, Divertin, bound IgCAM3, prevented cytokine-induced MLCK1 recruitment, myosin II regulatory light chain phosphorylation, and barrier dysfunction. Critically, Divertin did not inhibit MLCK enzymatic function, epithelial wound healing, or smooth muscle contraction, and in vivo toxicity studies failed to identify adverse effects. Divertin prevented acute TNF-induced barrier loss in vivo (mice) and ex vivo (human intestinal biopsies), and restored immune-mediated barrier loss in vivo (IL-10 knockout mice). Finally, Divertin delayed onset and prevented progression of experimental immune-mediated (T cell transfer) IBD, as indicated by barrier preservation and restoration, reduced mucosal immune activation, and enhanced survival. In a Phase I SBIR, we advanced this program through the discovery of hit compounds with improved activities. Hit compounds were discovered through a rigorous rank order screening funnel to identify compounds with suitable MLCK1 binding affinities, efficacy in preserving and restoring epithelial barrier function, and absence of enzymatic inhibitory activity. In this Phase II proposal, these hit compounds will be optimized with iterative structure activity relationship studies and tested for toxicity and efficacy in mouse models of IBD. This work will facilitate IND-enabling studies for a first-in-class and best-in-class barrier-restorative therapy to manage gastrointestinal and systemic diseases.