Human neutrophil elastase (HNE) is a potent protease that plays an important physiological role in many processes but is also involved in a variety of pathologies that affect the pulmonary system. Thus, compounds able to inhibit HNE proteolytic activity could represent effective therapeutics. We present here a new series of pyrazolopyridine and pyrrolopyridine derivatives as HNE inhibitors designed as modifications of our previously synthesized indazoles and indoles in order to evaluate effects of the change in position of the nitrogen and/or the insertion of an additional nitrogen in the scaffolds on biological activity and chemical stability. We obtained potent HNE inhibitors with IC₅₀ values in the low nanomolar range (10-50 nM), and some compounds exhibited improved chemical stability in phosphate buffer (t_1/2 > 6 h). Molecular modeling studies demonstrated that inhibitory activity was strictly dependent on the formation of a Michaelis complex between the OH group of HNE Ser195 and the carbonyl carbon of the inhibitor. Moreover, in silico ADMET calculations predicted that most of the new compounds would be optimally absorbed, distributed, metabolized, and excreted. Thus, these new and potent HNE inhibitors represent novel leads for future therapeutic development.

人中性粒细胞弹性蛋白酶 (HNE) 是一种强效蛋白酶，在许多过程中发挥重要的生理作用，但也参与影响肺系统的各种病理。因此，能够抑制 HNE 蛋白水解活性的化合物可以代表有效的治疗方法。我们在此展示了一系列新的吡唑并吡啶和吡咯并吡啶衍生物作为 HNE 抑制剂，设计为我们先前合成的吲唑和吲哚的修饰，以评估氮位置变化和/或在支架中插入额外氮的影响生物活性和化学稳定性。_{我们获得了具有 IC 50}的强效 HNE 抑制剂值在低纳摩尔范围（10-50 nM），一些化合物在磷酸盐缓冲液中表现出改善的化学稳定性（t _1/2 > 6 h）。分子模型研究表明，抑制活性严格依赖于 HNE Ser195 的 OH 基团与抑制剂的羰基碳之间形成的米氏复合物。此外，计算机ADMET 计算预测大多数新化合物将被最佳吸收、分布、代谢和排泄。因此，这些新的和有效的 HNE 抑制剂代表了未来治疗发展的新线索。