Design and synthesis of bioreductive prodrugs of class I histone deacetylase inhibitors and their biological evaluation in virally transfected acute myeloid leukemia cells.

Although histone deacetylase (HDAC) inhibitors show promise in treating various types of hematologic malignancies, they have some limitations, including poor pharmacokinetics and off-target side effects. Prodrug design has shown promise as an approach to improve pharmacokinetic properties and to improve target tissue specificity. In this work, several bioreductive prodrugs for class I HDACs were designed based on known selective HDAC inhibitors. The zinc-binding group of the HDAC inhibitors was masked with various nitroarylmethyl residues to make them substrates of nitroreductase (NTR). The developed prodrugs showed weak HDAC inhibitory activity compared to their parent inhibitors. The prodrugs were tested against wild-type and NTR-transfected THP1 cells. Cellular assays showed that both 2-nitroimidazole-based prodrugs 5 and 6 were best activated by the NTR and exhibited potent activity against NTR-THP1 cells. Compound 6 showed the highest cellular activity (GI50 = 77 nM) and exhibited moderate selectivity. Moreover, activation of prodrug 6 by NTR was confirmed by liquid chromatography-mass spectrometry analysis, which showed the release of the parent inhibitor after incubation with Escherichia coli NTR. Thus, compound 6 can be considered a novel prodrug selective for class I HDACs, which could be used as a good starting point for increasing selectivity and for further optimization.

Docking, Binding Free Energy Calculations and In Vitro Characterization of Pyrazine Linked 2-Aminobenzamides as Novel Class I Histone Deacetylase (HDAC) Inhibitors.

Class I histone deacetylases, HDAC1, HDAC2, and HDAC3, represent potential targets for cancer treatment. However, the development of isoform-selective drugs for these enzymes remains challenging due to their high sequence and structural similarity. In the current study, we applied a computational approach to predict the selectivity profile of developed inhibitors. Molecular docking followed by MD simulation and calculation of binding free energy was performed for a dataset of 2-aminobenzamides comprising 30 previously developed inhibitors. For each HDAC isoform, a significant correlation was found between the binding free energy values and in vitro inhibitory activities. The predictive accuracy and reliability of the best preforming models were assessed on an external test set of newly designed and synthesized inhibitors. The developed binding free-energy models are cost-effective methods and help to reduce the time required to prioritize compounds for further studies.

Synthesis, Molecular Docking and Biological Characterization of Pyrazine Linked 2-Aminobenzamides as New Class I Selective Histone Deacetylase (HDAC) Inhibitors with Anti-Leukemic Activity.

Class I histone deacetylases (HDACs) are key regulators of cell proliferation and they are frequently dysregulated in cancer cells. We report here the synthesis of a novel series of class-I selective HDAC inhibitors (HDACi) containing a 2-aminobenzamide moiety as a zinc-binding group connected with a central (piperazin-1-yl)pyrazine or (piperazin-1-yl)pyrimidine moiety. Some of the compounds were additionally substituted with an aromatic capping group. Compounds were tested in vitro against human HDAC1, 2, 3, and 8 enzymes and compared to reference class I HDACi (Entinostat (MS-275), Mocetinostat, CI994 and RGFP-966). The most promising compounds were found to be highly selective against HDAC1, 2 and 3 over the remaining HDAC subtypes from other classes. Molecular docking studies and MD simulations were performed to rationalize the in vitro data and to deduce a complete structure activity relationship (SAR) analysis of this novel series of class-I HDACi. The most potent compounds, including 19f, which blocks HDAC1, HDAC2, and HDAC3, as well as the selective HDAC1/HDAC2 inhibitors 21a and 29b, were selected for further cellular testing against human acute myeloid leukemia (AML) and erythroleukemic cancer (HEL) cells, taking into consideration their low toxicity against human embryonic HEK293 cells. We found that 19f is superior to the clinically tested class-I HDACi Entinostat (MS-275). Thus, 19f is a new and specific HDACi with the potential to eliminate blood cancer cells of various origins.

Development of Pyrazine-Anilinobenzamides as Histone Deacetylase HDAC1-3 Selective Inhibitors and Biological Testing Against Pancreas Cancer Cell Lines.

Class I histone deacetylase (HDAC) enzymes are key regulators of cell proliferation and are frequently dysregulated in cancer cells. Here we describe the synthesis of a novel series of class-I selective HDAC inhibitors containing anilinobenzamide moieties as ZBG connected with a central (piperazin-1-yl)pyrazine moiety. Compounds were tested in vitro against class-I HDAC1, 2, and 3 isoforms. Some highly potent HDAC inhibitors were obtained and were tested in pancreatic cancer cells and showed promising activity. Moreover, we summarize how the growth-inhibitory effects of these compounds can be determined in murine pancreatic cancer cell lines.