Synthesis, Structure-Activity Relationship, and Pharmacophore Modeling Studies of Pyrazole-3-Carbohydrazone Derivatives as Dipeptidyl Peptidase IV Inhibitors

Type 2 diabetes mellitus (T2DM) is a metabolic disease and a major challenge to healthcare systems around the world. Dipeptidyl peptidase IV (DPP-4), a serine protease, has been rapidly emerging as an effective therapeutic target for the treatment for T2DM. In this study, a series of novel DPP-4 inhibitors, featuring the pyrazole-3-carbohydrazone scaffold, have been discovered using an integrated approach of structure-based virtual screening, chemical synthesis, and bioassay. Virtual screening of SPECS Database, followed by enzymatic activity assay, resulted in five micromolar or low-to-mid-micromolar inhibitory level compounds (1-5) with different scaffold. Compound 1 was selected for the further structure modifications in considering inhibitory activity, structural variability, and synthetic accessibility. Seventeen new compounds were synthesized and tested with biological assays. Nine compounds (6e, 6g, 6k-l, and 7a-e) were found to show inhibitory effects against DPP-4. Molecular docking models give rational explanation about structure-activity relationships. Based on eight DPP-4 inhibitors (1-5, 6e, 6k, and 7d), the best pharmacophore model hypo1 was obtained, consisting of one hydrogen bond donor (HBD), one hydrogen bond acceptor (HBA), and two hydrophobic (HY) features. Both docking models and pharmacophore mapping results are in agreement with pharmacological results. The present studies give some guiding information for further structural optimization and are helpful for future DPP-4 inhibitors design.