Design and synthesis of pyridine-based benzamides as potent HDAC3 inhibitors as an armament against breast cancer with in vivo validation

Some novel benzamide derivatives with modified linker group were designed and synthesized as promising HDAC3-selective inhibitors. These compounds exerted promising antiproliferative potential compared to reference molecule CI994 while tested against several cancer cell lines. Notably, all these molecules exhibited nontoxicity towards normal human cell lines. The most promising molecule in series 7c exhibited ∼47-fold HDAC3 selectivity over HDAC2 isoform. Compound 7c induced apoptosis and cell cycle arrest in the G2/M phase in the 4T1 cell line. Moreover, compound 7c yielded a good in vivo pharmacokinetic profile. Notably, compound 7c markedly reduced tumor growth in the 4T1-Luc breast cancer xenograft model in female Balb/c mice. Compound 7c also upregulated apoptotic proteins namely caspase-3, caspase-7, and cytochrome c, and downregulated Bcl-2. The antitumor potential of compound 7c was further justified by the downregulation of EGFR and Ki-67 through Western blot analysis. Nevertheless, the HDAC3 inhibitory potency of compound 7c depicted strong and stable binding interaction at the HDAC3 active site. These findings validated that compound 7c is a promising HDAC3 inhibitor that can be further investigated for clinical translation to achieve emerging breast cancer therapeutics.