Development of Peptoid-Based Heteroaryl-Decorated Histone Deacetylase (HDAC) Inhibitors with Dual-Stage Antiplasmodial Activity

Dynamics of epigenetic modifications such as acetylation and deacetylation of histone proteins have been shown to be crucial for the life cycle development and survival of Plasmodium falciparum, the deadliest malaria parasite. In this study, we present a novel series of peptoid-based histone deacetylase (HDAC) inhibitors incorporating nitrogen-containing bicyclic heteroaryl residues as a new generation of antiplasmodial peptoid-based HDAC inhibitors. We synthesized the HDAC inhibitors by an efficient multicomponent protocol based on the Ugi four-component reaction. The subsequent screening of 16 compounds from our mini-library identified 6i as the most promising candidate, demonstrating potent activity against asexual blood-stage parasites (IC50 Pf3D7 = 30 nM; IC50 PfDd2 = 98 nM), low submicromolar activity against liver-stage parasites (IC50 PbEEF = 0.25 µM), excellent microsomal stability (t1/2 > 60 min), and low cytotoxicity to HEK293 cells (IC50 = 136 µM).