Discovery of Novel 4,5,6,7-Tetrahydro‑7<i>H</i>‑pyrazolo[3,4‑<i>c</i>]pyridin-7-one Derivatives as Orally Efficacious ATX Allosteric Inhibitors for the Treatment of Pulmonary Fibrosis

Pulmonary fibrosis (PF) is a progressive, fatal lung disease lacking effective treatments. Autotaxin (ATX) plays a crucial role in exacerbating inflammation and fibrosis, making it a promising target for fibrosis therapies. Herein, starting from PAT-409 (Cudetaxestat), a series of novel ATX inhibitors bearing 1H-indole-3-carboxamide, 4,5,6,7-tetrahydro-7H-pyrazolo[3,4-c]pyridin-7-one, or 4,5,6,7-tetrahydro-1H-pyrazolo[4,3-c]pyridine cores were designed based on the structure of ATX hydrophobic tunnel. The optimal 31 and 35 inhibited ATX with IC50 values of 2.8 and 0.7 nM, respectively. In a bleomycin-induced mouse PF model, both compounds significantly reduced fibrosis by regulating the TGF-β/Smad signaling pathway and downregulating collagen deposition. Furthermore, 35 exhibited both negligibly low hERG channel inhibition (IC50 > 30 μM) and remarkable microsomal stability. Notably, 35 was characterized by favorable pharmacokinetic properties (F = 69.5%) and excellent safety in vivo. Overall, 35 turned out to be a well-characterized potent and safe ATX inhibitor warranting further investigation for the treatment of PF.肺纤维化（Pulmonary fibrosis, PF）是一种进行性、致死性肺部疾病，目前尚无有效治疗手段。自分泌运动因子（Autotaxin, ATX）在加重炎症反应与肺纤维化进程中发挥关键作用，因此成为抗纤维化治疗的极具潜力的靶点。本研究以PAT-409（Cudetaxestat）为起始化合物，基于ATX疏水隧道的结构特征，设计了一系列以1H-吲哚-3-甲酰胺（1H-indole-3-carboxamide）、4,5,6,7-四氢-7H-吡唑并[3,4-c]吡啶-7-酮（4,5,6,7-tetrahydro-7H-pyrazolo[3,4-c]pyridin-7-one）或4,5,6,7-四氢-1H-吡唑并[4,3-c]吡啶（4,5,6,7-tetrahydro-1H-pyrazolo[4,3-c]pyridine）为母核的新型ATX抑制剂。优选得到的化合物31与35对ATX的半数抑制浓度（IC₅₀）分别为2.8 nM与0.7 nM。在博莱霉素诱导的小鼠肺纤维化模型中，两种化合物均可通过调控TGF-β/Smad信号通路并下调胶原沉积，显著减轻肺纤维化程度。此外，化合物35对hERG通道（human Ether-à-go-go Related Gene）的抑制活性极低（IC₅₀ > 30 μM），且具备优异的微粒体稳定性。值得注意的是，化合物35展现出良好的药代动力学特性（生物利用度F=69.5%）以及出色的体内安全性。综上，化合物35是一款经过充分表征的强效且安全的ATX抑制剂，值得进一步开展用于肺纤维化治疗的相关研究。