Design, Synthesis, and Biological Evaluation of New HDAC1 and HDAC2 Inhibitors Endowed with Ligustrazine as a Novel Cap Moiety

ntroduction: Histone deacetylases (HDACs) represent one of the most validated cancer targets. The inhibition of HDACs has been proven to be a successful strategy for the development of novel anticancer candidates.

Methods: This work describes design and synthesis of a new set of HDAC inhibitors (7a-c and 8a, b) utilizing ligustrazine as a novel cap moiety, and achieving the pharmacophoric features required to induce the desired inhibition.

Results: The newly synthesized derivatives were evaluated for their potential inhibitory activity toward two class I histone deacetylases, namely HDAC1 and HDAC2. The tested ligustrazine-based compounds were more potent toward HDAC2 (IC50 range: 53.7-205.4 nM) than HDAC1 (IC50 range: 114.3-2434.7 nM). Furthermore, the antiproliferative activities against two HDAC-expressing cancer cell lines; HT-29 and SH-SY5Y were examined by the MTT assay. Moreover, a molecular docking study of the designed HDAC inhibitors (7a-c and 8a,b) was carried out to investigate their binding pattern within their prospective targets; HDAC1 (PDB-ID: 4BKX) and HDAC2 (PDB-ID: 6G3O).

Discussion: Compound 7a was found to be the most potent analog in this study toward HDAC1 and HDAC2 with IC50 values equal 114.3 and 53.7 nM, respectively. Moreover, it was the most effective counterpart (IC50 = 1.60 µM), with 4.7-fold enhanced efficiency than reference drug Gefitinib (IC50 = 7.63 µM) against SH-SY5Y cells. Whereas, compound 8a (IC50 = 1.96 µM) was the most active member toward HT-29 cells, being 2.5-times more potent than Gefitinib (IC50 = 4.99 µM). Collectively, these results suggest that 7a merits further optimization and development as an effective new HDACI lead compound.