Chu Tifany, Karmakar Joy, Haggie Peter M, Tan Joseph-Anthony, Master Riya, Ramaswamy Keerthana, Verkman Alan S, Anderson Marc O, Cil Onur
Department of Pediatrics, University of California, San Francisco San Francisco CA USA
Department of Medicine, University of California, San Francisco San Francisco CA USA.
RSC Med Chem. 2023 Sep 14;14(11):2342-2347. doi: 10.1039/d3md00302g. eCollection 2023 Nov 15.
A loss of prosecretory Cl channel CFTR activity in the intestine is considered as the key cause of gastrointestinal problems in cystic fibrosis (CF): meconium ileus, distal intestinal obstruction syndrome (DIOS) and constipation. Since CFTR modulators have minimal effects on gastrointestinal symptoms, there is an unmet need for novel treatments for CF-associated gastrointestinal disorders. Meconium ileus and DIOS mainly affect the ileum (distal small intestine). SLC26A6 (putative anion transporter 1, PAT1) is a Cl/HCO exchanger at the luminal membrane of small intestinal epithelial cells which facilitates Cl and fluid absorption. We recently identified first-in-class PAT1 inhibitors by high-throughput screening. Isoxazolopyrimidine PAT1-A01 was a hit compound, which had low potency (IC 5.2 μM) for SLC26A6 inhibition precluding further preclinical development. Here we performed structure-activity relationship studies to optimize isoxazolopyrimidine SLC26A6 inhibitors and tested a potent inhibitor in mouse models of intestinal fluid absorption. Structure-activity studies of 377 isoxazolopyrimidine analogs identified PAT1-A0030 (ethyl 4-(benzyl(methyl)amino)-3-methylisoxazolo[5,4-]pyrimidine-6-carboxylate) as the most potent SLC26A6 inhibitor with a 1.0 μM IC. Selectivity studies showed that PAT1-A030 has no activity on relevant ion transporters/channels (SLC26A3, SLC26A4, SLC26A9, CFTR, TMEM16A). In a closed-loop model of intestinal fluid absorption, intraluminal PAT1-A0030 treatment inhibited fluid absorption in the ileum of wild-type and CF mice () with >90% prevention of a decrease in loop fluid volume and loop weight/length ratio at 30 minutes. These results suggest that SLC26A6 is the key transporter mediating Cl and fluid absorption in the ileum and SLC26A6 inhibitors are novel drug candidates for treatment of CF-associated small intestinal disorders.
肠道中促分泌性氯离子通道CFTR活性丧失被认为是囊性纤维化（CF）患者出现胃肠道问题的关键原因，这些问题包括胎粪性肠梗阻、远端肠梗阻综合征（DIOS）和便秘。由于CFTR调节剂对胃肠道症状的影响极小，因此对于CF相关胃肠道疾病的新型治疗方法仍存在未满足的需求。胎粪性肠梗阻和DIOS主要影响回肠（远端小肠）。SLC26A6（推定阴离子转运体1，PAT1）是小肠上皮细胞腔膜上的一种Cl/HCO交换体，可促进Cl和液体的吸收。我们最近通过高通量筛选鉴定出了一流的PAT1抑制剂。异恶唑并嘧啶PAT1-A01是一种命中化合物，其对SLC26A6抑制的效力较低（IC5.2 μM），因此无法进行进一步的临床前开发。在此，我们进行了构效关系研究以优化异恶唑并嘧啶SLC26A6抑制剂，并在肠道液体吸收的小鼠模型中测试了一种强效抑制剂。对377种异恶唑并嘧啶类似物的构效研究确定PAT1-A0030（4-(苄基(甲基)氨基)-3-甲基异恶唑并[5,4-b]嘧啶-6-羧酸乙酯）是最有效的SLC26A6抑制剂，IC为1.0 μM。选择性研究表明，PAT1-A030对相关离子转运体/通道（SLC26A3、SLC26A4、SLC26A9、CFTR、TMEM16A）无活性。在肠道液体吸收的闭环模型中，腔内给予PAT1-A0030可抑制野生型和CF小鼠回肠中的液体吸收（），在30分钟时可>90%预防肠襻液体体积和肠襻重量/长度比的降低。这些结果表明，SLC26A6是介导回肠中Cl和液体吸收的关键转运体，SLC26A6抑制剂是治疗CF相关小肠疾病的新型候选药物。
