Discovery of novel class of histone deacetylase inhibitors as potential anticancer agents

The Groebke-Blackburn-Bienaymé (GBB) reaction: A powerful tool for generating diverse heterocyclic scaffold libraries in anticancer drug discovery

The Groebke-Blackburn-Bienaymé (GBB) reaction is a versatile multi-component (MCR) synthetic methodology that has transformed anticancer drug discovery by enabling the rapid and efficient generation of diverse heterocyclic scaffolds. These scaffolds, such as imidazo[1,2-a]pyridines, imidazo[1,2-a]pyrimidines, and their derivatives, are highly valuable moieties for targeting critical cancer pathways. The modular nature of the GBB reaction, coupled with post-reaction modifications, allows the design of compounds with tailored structures and enhanced pharmacological properties. GBB-derived compounds exhibit broad anticancer potential by modulating diverse molecular targets. These include protein kinases (e.g. Rock2, Gsk3β, B-Raf), microtubule dynamics via tubulin inhibition, and G-quadruplex DNA stabilization in oncogene promoters (e.g., c-MYC, BCL2), disrupting key mechanisms of tumour progression. Moreover, they target epigenetic regulators such as HDACs, CBP/P300 bromodomains, and BET bromodomains, affecting transcriptional regulation and chromatin remodeling. Immune checkpoints (e.g., PD-1/PD-L1), enzymes such as autotaxin, TDP1, and Hsp90, as well as apoptotic regulators (e.g., Bcl-2, BAG3), are also effectively inhibited. More importantly, these compounds address challenging targets, including KRAS G12C mutations and the menin-MLL interaction, offering solutions to previously "undruggable" pathways. The unparalleled efficiency of GBB reaction and its ability to generate structurally diverse, bioactive compounds spanning multiple oncogenic mechanisms highlights its central role in advancing anticancer drug discovery and its transformative impact on therapeutic innovation.

Anticancer benzimidazole derivatives as inhibitors of epigenetic targets: a review article

Cancer is one of the leading causes of morbidity and mortality worldwide. One of the primary causes of cancer development and progression is epigenetic dysregulation, which is a heritable modification that alters gene expression without changing the DNA sequence. Therefore, targeting these epigenetic changes has emerged as a promising therapeutic strategy. Benzimidazole derivatives have gained attention for their potent epigenetic modulatory effects as they interact with various epigenetic targets, including DNA methyltransferases, histone deacetylases and histone methyltransferases. This review provides a comprehensive overview of benzimidazole derivatives that inhibit different acetylation and methylation reader, writer and eraser epigenetic targets. Herein, we emphasize the therapeutic potential of these compounds in developing targeted, less toxic cancer therapies. Presently, some promising benzimidazole derivatives have entered clinical trials and shown great advancements in the fields of hematological and solid malignancy therapies. Accordingly, we highlight the recent advancements in benzimidazole research as epigenetic agents that could pave the way for designing new multi-target drugs to overcome resistance and improve clinical outcomes for cancer patients. This review can help researchers in designing new anticancer benzimidazole derivatives with better properties.

Revisiting the GBB reaction and redefining its relevance in medicinal chemistry: A review

Multicomponent reactions (MCRs) have significant relevance in the field of synthetic chemistry, and in recent times one of the MCR variants, named the Groebke-Blackburn-Bienaymé (GBB) reaction, has attracted massive attention for the synthesis of biologically important scaffolds. The present review elaborates on the chemical advancement reported for the GBB reaction with an emphasis on the role of various catalytic systems. Further, the role of the GBB reaction has been redefined as a standard protocol for the synthesis of an array of potential bioactive compounds.

HDAC9 and miR-512 Regulate CAGE-Promoted Anti-Cancer Drug Resistance and Cellular Proliferation

Histone deacetylase 9 (HDAC9) is known to be upregulated in various cancers. Cancer-associated antigens (CAGEs) are cancer/testis antigens that play an important role in anti-cancer drug resistance. This study aimed to investigate the relationship between CAGEs and HDAC9 in relation to anti-cancer drug resistance. AGSR cells with an anti-cancer drug-resistant phenotype showed higher levels of CAGEs and HDAC9 than normal AGS cells. CAGEs regulated the expression of HDAC9 in AGS and AGSR cells. CAGEs directly regulated the expression of HDAC9. Rapamycin, an inducer of autophagy, increased HDAC9 expression in AGS, whereas chloroquine decreased HDAC9 expression in AGSR cells. The downregulation of HDAC9 decreased the autophagic flux, invasion, migration, and tumor spheroid formation potential in AGSR cells. The TargetScan analysis predicted that miR-512 was a negative regulator of HDAC9. An miR-512 mimic decreased expression levels of CAGEs and HDAC9. The miR-512 mimic also decreased the autophagic flux, invasion, migration, and tumor spheroid forming potential of AGSR cells. The culture medium of AGSR increased the expression of HDAC9 and autophagic flux in AGS. A human recombinant CAGE protein increased HDAC9 expression in AGS cells. AGSR cells displayed higher tumorigenic potential than AGS cells. Altogether, our results show that CAGE-HDAC9-miR-512 can regulate anti-cancer drug resistance, cellular proliferation, and autophagic flux. Our results can contribute to the understanding of the molecular roles of HDAC9 in anti-cancer drug resistance.

Significance of Five-Membered Heterocycles in Human Histone Deacetylase Inhibitors

Five-membered heteroaromatic rings, in particular, have gained prominence in medicinal chemistry as they offer enhanced metabolic stability, solubility and bioavailability, crucial factors in developing effective drugs. The unique physicochemical properties and biological effects of five-membered heterocycles have positioned them as key structural motifs in numerous clinically effective drugs. Hence, the exploration of five-ring heterocycles remains an important research area in medicinal chemistry, with the aim of discovering new therapeutic agents for various diseases. This review addresses the incorporation of heteroatoms such as nitrogen, oxygen and sulfur into the aromatic ring of these heterocyclic compounds, enhancing their polarity and facilitating both aromatic stacking interactions and the formation of hydrogen bonds. Histone deacetylases are present in numerous multiprotein complexes within the epigenetic machinery and play a central role in various cellular processes. They have emerged as important targets for cancer, neurodegenerative diseases and other therapeutic indications. In histone deacetylase inhibitors (HDACi's), five-ring heterocycles perform various functions as a zinc-binding group, a linker or head group, contributing to binding activity and selective recognition. This review focuses on providing an up-to-date overview of the different five-membered heterocycles utilized in HDACi motifs, highlighting their biological properties. It summarizes relevant publications from the past decade, offering insights into the recent advancements in this field of research.

Inherited Retinal Degeneration: Towards the Development of a Combination Therapy Targeting Histone Deacetylase, Poly (ADP-Ribose) Polymerase, and Calpain

Inherited retinal degeneration (IRD) represents a diverse group of gene mutation-induced blinding diseases. In IRD, the loss of photoreceptors is often connected to excessive activation of histone-deacetylase (HDAC), poly-ADP-ribose-polymerase (PARP), and calpain-type proteases (calpain). Moreover, the inhibition of either HDACs, PARPs, or calpains has previously shown promise in preventing photoreceptor cell death, although the relationship between these enzyme groups remains unclear. To explore this further, organotypic retinal explant cultures derived from wild-type mice and rd1 mice as a model for IRD were treated with different combinations of inhibitors specific for HDAC, PARP, and calpain. The outcomes were assessed using in situ activity assays for HDAC, PARP, and calpain, immunostaining for activated calpain-2, and the TUNEL assay for cell death detection. We confirmed that inhibition of either HDAC, PARP, or calpain reduced rd1 mouse photoreceptor degeneration, with the HDAC inhibitor Vorinostat (SAHA) being most effective. Calpain activity was reduced by inhibition of both HDAC and PARP whereas PARP activity was only reduced by HDAC inhibition. Unexpectedly, combined treatment with either PARP and calpain inhibitors or HDAC and calpain inhibitors did not produce synergistic rescue of photoreceptors. Together, these results indicate that in rd1 photoreceptors, HDAC, PARP, and calpain are part of the same degenerative pathway and are activated in a sequence that begins with HDAC and ends with calpain.