Human neutrophil elastase (HNE) is a potent serine protease belonging to the chymotrypsin family. It is an important target for the development of novel and selective inhibitors for the treatment of inflammatory diseases, especially pulmonary pathologies. Here, we report the synthesis and biological evaluation of a new series of HNE inhibitors with a pyrrolo[2,3-b]pyridine scaffold, which is an isomer of our previously reported indazoles, in order to assess how a shift of the nitrogen from position 2 to position 7 influences activity. The majority of new compounds were effective HNE inhibitors and had IC₅₀ values in the micromolar/submicromolar range, with some compounds active in low nanomolar levels. For example, 2a and 2b inhibited HNE with IC₅₀ values of 15 and 14 nM, respectively. Molecular modeling of compounds differing in the position of heteroatom(s) in the bicyclic moiety and in the oxadiazole ring demonstrated that the calculated geometries of enzyme-inhibitor complexes were in agreement with the observed biological activities. Docking experiments showed that orientation of the active pyrrolo[2,3-b]pyridines in the HNE catalytic triad Ser195-His57-Asp102 correlated with effectiveness of the inhibitor interaction with the enzyme. Thus, the pyrrolo[2,3-b]pyridine scaffold represents a novel scaffold for the development of potent HNE inhibitors.

人嗜中性粒细胞弹性蛋白酶（HNE）是一种有效的丝氨酸蛋白酶，属于胰凝乳蛋白酶家族。它是开发用于治疗炎性疾病，尤其是肺部疾病的新型和选择性抑制剂的重要目标。在这里，我们报道了带有吡咯并[2,3- b ]吡啶骨架的一系列新的HNE抑制剂的合成和生物学评估，吡咯并[2,3- b ]吡啶骨架是我们先前报道的吲唑的异构体，目的是评估氮如何从氮转移。从位置2到位置7影响活动。大多数新化合物是有效的HNE抑制剂，IC ₅₀值在微摩尔/亚微摩尔范围内，有些化合物在低纳摩尔水平下具有活性。例如2a和2b抑制HNE的IC ₅₀值分别为15和14 nM。在双环部分和恶二唑环中，杂原子位置不同的化合物的分子模型表明，酶抑制剂复合物的几何结构与观察到的生物活性相符。对接实验表明，HNE催化三联体Ser195-His57-Asp102中活性吡咯并[2,3- b ]吡啶的取向与抑制剂与酶的相互作用有关。因此，吡咯并[2，3- b ]吡啶支架代表了用于开发有效的HNE抑制剂的新型支架。