由于现有药物无法有效控制多达40%的中度至重度炎症性肠病（IBD）患者，迫切需要开发相应的治疗方法。谷氨酸羧肽酶II（GCPII）已被确定是一个很有潜力的治疗目标。该酶在正常空肠和结肠中表达较低，但在IBD患者和临床前结肠炎模型的活检组织中表达显著上调。本文中，我们设计了一类用于口服的GCPII抑制剂，具有肠道限制性，使用体外和体内模型评估了其疗效和机制。主要的抑制剂（S）-IBD3540具有较高的有效浓度（半数最大抑制浓度为4纳摩尔），选择性强，以及对慢性和急性啮齿动物结肠炎模型具有较好的疗效。在由左右旋糖苷硫酸钠诱导的结肠炎中，口服（S）-IBD3540可以抑制超过75%的结肠GCPII活性，剂量依赖性地改善肠道临床和组织病变，并显著减轻单核细胞炎症反应。对于IL-10缺乏小鼠的自发性结肠炎，疾病开始后每日一次口服（S）-IBD3540可以改善疾病状况，使结肠组织恢复正常，并减轻炎症反应，具体体现为降低大便脂联素2和结肠促炎细胞因子/趋化因子，包括肿瘤坏死因子-α和IL-17的含量。通过使用原代人类结肠上皮液-气界面单层来研究机制，我们进一步发现（S）-IBD3540通过降低屏障通透性，调节紧密连接蛋白表达，并减少初始半胱氨酸蛋白酶-3的激活来保护免受湿度下引起的氧化应激损伤。综上所述，本研究证明了用于肠道的局部抑制失调的胃肠道GCPII的治疗方法，即通过口服活性小分子（S）-IBD3540进行肠道限制，是一种很有希望的IBD治疗方法。

There is an urgent need to develop therapeutics for inflammatory bowel disease (IBD) because up to 40% of patients with moderate-to-severe IBD are not adequately controlled with existing drugs. Glutamate carboxypeptidase II (GCPII) has emerged as a promising therapeutic target. This enzyme is minimally expressed in normal ileum and colon, but it is markedly up-regulated in biopsies from patients with IBD and preclinical colitis models. Here, we generated a class of GCPII inhibitors designed to be gut-restricted for oral administration, and we interrogated efficacy and mechanism using in vitro and in vivo models. The lead inhibitor, (S)-IBD3540, was potent (half maximal inhibitory concentration = 4 nanomolar), selective, gut-restricted (AUCcolon/plasma > 50 in mice with colitis), and efficacious in acute and chronic rodent colitis models. In dextran sulfate sodium-induced colitis, oral (S)-IBD3540 inhibited >75% of colon GCPII activity, dose-dependently improved gross and histologic disease, and markedly attenuated monocytic inflammation. In spontaneous colitis in interleukin-10 (IL-10) knockout mice, once-daily oral (S)-IBD3540 initiated after disease onset improved disease, normalized colon histology, and attenuated inflammation as evidenced by reduced fecal lipocalin 2 and colon pro-inflammatory cytokines/chemokines, including tumor necrosis factor-α and IL-17. Using primary human colon epithelial air-liquid interface monolayers to interrogate the mechanism, we further found that (S)-IBD3540 protected against submersion-induced oxidative stress injury by decreasing barrier permeability, normalizing tight junction protein expression, and reducing procaspase-3 activation. Together, this work demonstrated that local inhibition of dysregulated gastrointestinal GCPII using the gut-restricted, orally active, small-molecule (S)-IBD3540 is a promising approach for IBD treatment.