Drug Repurposing of Quisinostat to Discover Novel <i>Plasmodium falciparum</i> HDAC1 Inhibitors with Enhanced Triple-Stage Antimalarial Activity and Improved Safety

Abstract

Our previous work found that the clinical histone deacetylase (HDAC) inhibitor quisinostat exhibited a significant antimalarial effect but with severe toxicity. In this work, 35 novel derivatives were designed and synthesized based on quisinostat as the lead compound, and their in vitro antimalarial activities and cytotoxicities were systematically evaluated. Among them, <b>JX35</b> showed potent inhibition against both wild-type and multidrug-resistant parasite strains and displayed a significant in vivo killing effect against all life cycles of parasites, including the blood stage, liver stage, and gametocyte stage, indicating its potential for the simultaneous treatment, chemoprevention, and blockage of malaria transmission. Compared with quisinostat, <b>JX35</b> exhibited stronger antimalarial efficacy, more adequate safety, and good pharmacokinetic properties. Additionally, mechanistic studies via molecular docking studies, induced <i>Pf</i>HDAC1/2 knockdown assays, and <i>Pf</i>HDAC1 enzyme inhibition assays jointly indicated that the antimalarial target of <b>JX35</b> was <i>Pf</i>HDAC1. In summary, we discovered the promising candidate <i>Pf</i>HDAC1 inhibitor <b>JX35</b>, which showed stronger triple-stage antimalarial effects and lower toxicity than quisinostat.