Design, synthesis, and evaluation of novel hydrazide and hydroxamate derivatives as potent antileukemic agents with preferential HDAC-2 inhibitory activity over class I isoform

The development of isoform-selective histone deacetylase (HDAC) inhibitors remains a promising frontier for targeted cancer therapy, offering a strategic opportunity to maximize therapeutic efficacy while minimizing the adverse side effects of pan-HDAC inhibition. In this study, we present a novel series of 4-iodo-3-nitrophenyl-capped hydrazide and hydroxamate compounds that were developed, and investigated for potential to function as effective and preferential HDAC-2 inhibitors. In vitro enzyme assays revealed that this new scaffold prefers the HDAC-2 isoform over HDAC-1, which differs significantly from the non-selective reference medication, Vorinostat (SAHA). Upon testing these compounds with the propidium iodide (PI) fluorescence assay across many human cancer cell lines, we observed a remarkable, tissue-specific sensitivity. The foremost derivatives (7a, 7c, and 7d) exhibited much greater efficacy in inhibiting the growth of B-cell acute lymphoblastic (SEM) cells, exhibiting IC50 values ranging from 3.18 to 4.17 mM, surpassing the reference drug Vorinostat, which presented an IC50 of 5.23 mM. Western blot analyses in SEM cells revealed that the lead compound 7a bound to its intracellular target, resulting in an approximately 59% reduction in total HDAC-2 protein levels. ... mehrFlow cytometry revealed that a significant reduction in HDAC-2 led to cancer cells being arrested at the key G2/M phase of the cell cycle, with 46.22% of cells detained there compared to merely 7.21% in untreated controls. Subsequent analysis using Annexin V/PI labeling demonstrated that this cell cycle arrest results in a significant elevation of programmed cell death, increasing total apoptosis to 31.12%, while maintaining non-specific necrosis at a minimal 4.29%. Taken together, these findings indicate that the 4-iodo-3-nitrophenyl compounds are effective tools for the targeted treatment of leukemia, displaying preferential HDAC-2 inhibitory activity among the evaluated class I isoforms.