Synthesis and evaluation of novel N-arylamide-quinoline derivatives as HDAC isoform-selective inhibitors: in vitro and in vivo anticancer efficacy and pharmacokinetic studies.

Epigenetic dysregulation plays a critical role in tumorigenesis and cancer progression. The development of isoform-selective histone deacetylase (HDAC) inhibitors has emerged as a promising strategy in cancer therapy. In this study, based on our previously identified hit compounds, a series of novel N-arylamide-quinoline derivatives were rationally designed and synthesized as HDAC isoform-selective inhibitors with improved efficacy and reduced toxicity. Among them, 6b exhibited potent inhibitory activity against HDAC1, 2, 3, and 10, while showing no activity against HDAC4-9, a selectivity profile further supported by molecular docking and molecular dynamics simulation. 6b demonstrated significant antiproliferative effects against HL-60, CCRF-CEM, and HepG2 cancer cells. In vitro toxicity assays revealed a high selectivity index for this compound, markedly superior to that of the parent compounds. Mechanistic studies showed that it induced hyperacetylation of histone H3 in a concentration-dependent manner, downregulated Rb protein and caspase-8 precursor, and modulated the expression of BAX, BAK, and BCL-2, leading to extrinsic apoptosis and G0/G1 phase cell cycle arrest. In vivo, 6b exhibited potent antitumor activity with no apparent toxicity following both intragastric administration and intraperitoneal injection. Notably, intraperitoneal delivery resulted in enhanced efficacy. Pharmacokinetic studies further characterized the in vivo behavior of this compound via both routes. Overall, hit compound 6b displays favorable biological properties and represents a promising candidate for further anticancer drug development, with subsequent studies focusing on the optimization of its drug-like properties.