Design, Synthesis, and Biological Evaluation of Pyrazoline-Based Hydroxamic Acid Derivatives as Aminopeptidase N (APN) Inhibitors.

Aminopeptidase N (APN) has been recognized as a target for anticancer treatment due to its overexpression on diverse malignant tumor cells and association with cancer invasion, metastasis and angiogenesis. Herein we describe the synthesis, biological evaluation, and structure-activity relationship study of two new series of pyrazoline analogues as APN inhibitors. Among these compounds, 5-(2-(2-(hydroxyamino)-2-oxoethoxy)phenyl)-3-phenyl-4,5-dihydro-1H-pyrazole-1-carboxamide (compound 13 e) showed the best APN inhibition with an IC value of 0.16±0.02 μm, which is more than one order of magnitude lower than that of bestatin (IC =9.4±0.5 μm). Moreover, compound 13 e was found to inhibit the proliferation of diverse carcinoma cells and to show potent anti-angiogenesis activity. At the same concentration, compound 13 e presents significantly higher anti-angiogenesis activity than bestatin in human umbilical vein endothelial cells (HUVECs) capillary tube formation assays. The putative binding mode of 13 e in the active site of APN is also discussed.