Belinostat: First Global Approval

Distribution, metabolism, and excretion of [14C] purinostat mesylate, a novel selective HDAC I/IIb inhibitor, in rats analyzed by high-performance liquid chromatography coupled with LTQ orbitrap mass spectrometry/radioactivity monitoring

Purinostat Mesylate (PM) is a novel and highly efficient selective histone deacetylase (HDAC) I/IIb inhibitor for hematologic tumor treatment that was granted Investigational New Drug (IND) approval for clinical investigation by the National Medical Products Administration and is currently in phase IIb clinical trials for relapsed/refractory diffuse large B-cell lymphoma. In this paper, the excretion, distribution, and metabolism properties of this IND were researched by High-Performance Liquid Chromatography coupled with LTQ Orbitrap Mass Spectrometry/Radioactivity Monitoring (HPLC-LTQ-Orbitrap-MS/RAM) and liquid scintillation counting. Following a single intravenous dose of [14C] PM to rats, a total of 98.49 % of the dose was recovered from intact rats within 0-168 h post-dose, with 14.16 % in urine and 83.15 % in feces, most of which was recovered within the first 24 h post-dose. For bile duct cannulated rats, a total of 95.54 % of the dose was recovered, with 62.37 % in bile, 23.37 % in urine and 8.58 % in feces within 0-72 h post-dose, suggesting that [14C] PM was excreted mainly into feces via biliary excretion. [14C] PM was distributed widely and eliminated rapidly throughout the body, with the lung, liver, kidney and intestine as the main organs. Interestingly, slow elimination was observed in the spleen, which could benefit the functional restoration of the spleen in hematological tumors. In terms of metabolism, [14C] PM underwent an extensive metabolic transformation in rats. Fourteen metabolites were tentatively identified, with major phase I metabolic pathways encompassing reduction, N-dealkylation, and oxidative deamination. Concomitantly, the primary phase II metabolic routes involved acetylation and glucuronic acid conjugation. This study was the first comprehensive PM pharmacokinetic study utilizing [14C] isotope labeling technology.

Cholinesterase-based inhibitors as multitarget small molecules for the therapy of Alzheimer's disease

Herein, we have summarized the most significant results that we have communicated from our laboratories in the last thirty years, highlighting the most potent and attractive ChEIs based hit(lead)-Multitarget Small Molecules, such as (S)-p-methoxytacripyrine (1), ASS234 (2), Contilisant (3), and Contilistat (4), that we have identified in the search for new chemical entities for the therapy of Alzheimer's disease.

Development of Hydrazide-Based HDAC6 Selective Inhibitors for Treating NLRP3 Inflammasome-Related Diseases

Previously, we found that hydrazide can serve as zinc binding groups for selective HDAC6 inhibitors and identified the first hydrazide-based HDAC6 inhibitor, 35m, which exhibited modest isoform selectivity. This study aimed to improve the HDAC6 selectivity of 35m, thereby reducing its side effects. Extensive structure-activity relationship studies revealed that the introduction of fluorine atoms at the 2 and 5 positions of the linker phenyl ring in compound 35m significantly enhanced its HDAC6 selectivity while maintaining its potency. The representative compound 9m demonstrated an IC50 of 0.021 μM against HDAC6, exhibiting at least 335-fold selectivity over other isoforms, along with favorable pharmacokinetic properties and improved safety profiles. Compound 9m inhibits the activation of NLRP3 inflammasome and significantly alleviates symptoms in multiple NLRP3 inflammasome-related disease models, including acute peritoneal, inflammatory bowel disease, and psoriasis. This study enriches the design strategies for selective HDAC6 inhibitors and provides a lead compound for NLRP3 inflammasome-related diseases.

Drug Discovery for Histone Deacetylase Inhibition: Past, Present and Future of Zinc-Binding Groups

Histone deacetylases (HDACs) are key regulators of gene expression, influencing chromatin remodeling and playing a crucial role in various physiological and pathological processes. Aberrant HDAC activity has been linked to cancer, neurodegenerative disorders, and inflammatory diseases, making these enzymes attractive therapeutic targets. HDAC inhibitors (HDACis) have gained significant attention, particularly those containing zinc-binding groups (ZBGs), which interact directly with the catalytic zinc ion in the enzyme's active site. The structural diversity of ZBGs profoundly impacts the potency, selectivity, and pharmacokinetics of HDACis. While hydroxamic acids remain the most widely used ZBGs, their limitations, such as metabolic instability and off-target effects, have driven the development of alternative scaffolds, including ortho-aminoanilides, mercaptoacetamides, alkylhydrazides, oxadiazoles, and more. This review explores the structural and mechanistic aspects of different ZBGs, their interactions with HDAC isoforms, and their influence on inhibitor selectivity. Advances in structure-based drug design have allowed the fine-tuning of HDACi pharmacophores, leading to more selective and efficacious compounds with improved drug-like properties. Understanding the nuances of ZBG interactions is essential for the rational design of next-generation HDACis, with potential applications in oncology, neuroprotection, and immunotherapy.

Harnessing HDAC-targeted oleanolic acid derivatives for combined anti-cancer and hepatoprotective effects

The development of anti-tumor drugs with hepatoprotective properties has always been highly valued due to their dual capabilities of safeguarding the liver and combating tumors. Moreover, when used in conjunction with specific chemotherapy drugs, they can enhance the efficacy of cancer treatment while simultaneously reducing liver damage caused by chemotherapeutic agents. Our research focused on oleanolic acid (OA), a natural compound known for its liver-protective effects. By incorporating an HDAC-targeting pharmacophore at the 28-COOH site of OA, we aimed to identify compounds that offer dual benefits of liver protection and anti-tumor activity. Compound 2c demonstrated significant inhibitory effects on the growth of RS4;11, K562, and RPMI8226 cells, showed cytotoxicity against HepG2 liver cancer cells, and exhibited favorable selectivity towards normal liver cells. Moreover, compound 2c induced apoptosis in HepG2 cells and arrested cell cycle progression at the G2 phase. Further investigations revealed that compound 2c could alleviate cisplatin-induced liver cell damage and animal liver injury by activating the NRF2/HO-1 pathway. In a HepG2 xenograft model, intravenous administration of compound 2c effectively suppressed tumor growth without eliciting adverse reactions, while enhanced NRF2 and HO-1 expression was observed in the liver tissues of mice treated with compound 2c. Besides, co-administration of cisplatin with compound 2c could significantly enhance the anti-tumor efficacy of cisplatin but minimize liver injury caused by the treatment of cisplatin. Our study provides a lead compound possessing hepatoprotective and antitumor activity, offering a novel strategy to avoid pharmacological liver injury.

Epigenetic marvels: exploring the landscape of colorectal cancer treatment through cutting-edge epigenetic-based drug strategies

Epigenetics is currently considered the investigation of inheritable changes in gene expression that do not rely on DNA sequence alteration. Significant epigenetic procedures are involved, such as DNA methylations, histone modifications, and non-coding RNA actions. It is confirmed through several investigations that epigenetic changes are associated with the formation, development, and metastasis of various cancers, such as colorectal cancer (CRC). The difference between epigenetic changes and genetic mutations is that the former could be reversed or prevented; therefore, cancer treatment and prevention could be achieved by restoring abnormal epigenetic events within the neoplastic cells. These treatments, consequently, cause the anti-tumour effects augmentation, drug resistance reduction, and host immune response stimulation. In this article, we begin our survey by exploring basic epigenetic mechanisms to understand epigenetic tools and strategies for treating colorectal cancer in monotherapy and combination with chemotherapy or immunotherapy.

Histone Deacetylase (HDAC) Inhibitors as a Novel Therapeutic Option Against Fibrotic and Inflammatory Diseases

Histone deacetylases (HDACs) are enzymes that play an essential role in the onset and progression of cancer. As a consequence, a variety of HDAC inhibitors (HDACis) have been developed as potent anticancer agents, several of which have been approved by the FDA for cancer treatment. However, recent accumulated research results have suggested that HDACs are also involved in several other pathophysiological conditions, such as fibrotic, inflammatory, neurodegenerative, and autoimmune diseases. Very recently, the HDAC inhibitor givinostat has been approved by the FDA for an indication beyond cancer: the treatment of Duchenne muscular dystrophy. In recent years, more and more HDACis have been developed as tools to understand the role that HDACs play in various disorders and as a novel therapeutic approach to fight various diseases other than cancer. In the present perspective article, we discuss the development and study of HDACis as anti-fibrotic and anti-inflammatory agents, covering the period from 2020-2024. We envision that the discovery of selective inhibitors targeting specific HDAC isozymes will allow the elucidation of the role of HDACs in various pathological processes and will lead to the development of promising treatments for such diseases.

Epigenetics-targeted drugs: current paradigms and future challenges

Epigenetics governs a chromatin state regulatory system through five key mechanisms: DNA modification, histone modification, RNA modification, chromatin remodeling, and non-coding RNA regulation. These mechanisms and their associated enzymes convey genetic information independently of DNA base sequences, playing essential roles in organismal development and homeostasis. Conversely, disruptions in epigenetic landscapes critically influence the pathogenesis of various human diseases. This understanding has laid a robust theoretical groundwork for developing drugs that target epigenetics-modifying enzymes in pathological conditions. Over the past two decades, a growing array of small molecule drugs targeting epigenetic enzymes such as DNA methyltransferase, histone deacetylase, isocitrate dehydrogenase, and enhancer of zeste homolog 2, have been thoroughly investigated and implemented as therapeutic options, particularly in oncology. Additionally, numerous epigenetics-targeted drugs are undergoing clinical trials, offering promising prospects for clinical benefits. This review delineates the roles of epigenetics in physiological and pathological contexts and underscores pioneering studies on the discovery and clinical implementation of epigenetics-targeted drugs. These include inhibitors, agonists, degraders, and multitarget agents, aiming to identify practical challenges and promising avenues for future research. Ultimately, this review aims to deepen the understanding of epigenetics-oriented therapeutic strategies and their further application in clinical settings.

Discovery of a Novel and Potent Dual-Targeting Inhibitor of ATM and HDAC2 Through Structure-Based Virtual Screening for the Treatment of Testicular Cancer

Purpose

Dual inhibition of ataxia telangiectasia mutated (ATM) and histone deacetylase 2 (HDAC2) may be a potential strategy to improve antitumor efficacy in testicular cancer.

Methods

A combined virtual screening protocol including pharmacophore modeling and molecular docking was used for screening potent dual-target ATM/HDAC2 inhibitors. In order to obtain the optimal lead compound, the dual ATM/HDAC2 inhibitory activity of the screened compounds was further evaluated using enzyme inhibition methods. The binding stability of the optimal compound to the dual targets was verified by molecular dynamics (MD) simulation. MTT assay and in vivo antitumor experiment were performed to validate antitumor efficacy of the optimal compound in testicular cancer.

Results

Here, we successfully discovered six potent dual-target ATM/HDAC2 inhibitors (AMHs 1-6), which exhibited good inhibitory activity against both ATM and HDAC2. Among them, AMH-4 showed strong inhibitory activity against both ATM (IC50 = 1.12 ± 0.03 nM) and HDAC2 (IC50 = 3.04 ± 0.08 nM). MD simulation indicated that AMH-4 binds to ATM and HDAC2 with satisfactory stability. Importantly, AMH-4 had significant antiproliferative activity on human testicular tumor cells, especially NTERA-2 cL.D1 cells, and no inhibitory effect on normal human testicular cells. In vivo experiments exhibited that AMH-4 was more effective than lartesertib and vorinostat in inhibiting the growth of NTERA-2 cL.D1 xenograft tumors with low toxicity.

Conclusion

Overall, these results suggest that AMH-4 is an effective and low toxicity candidate for the treatment of testicular germ cell tumors.

Unveiling the role of histone deacetylases in neurological diseases: focus on epilepsy

Epilepsy remains a prevalent chronic neurological disease that is featured by aberrant, recurrent and hypersynchronous discharge of neurons and poses a great challenge to healthcare systems. Although several therapeutic interventions are successfully utilized for treating epilepsy, they can merely provide symptom relief but cannot exert disease-modifying effect. Therefore, it is of urgent need to explore other potential mechanism to develop a novel approach to delay the epileptic progression. Since approximately 30 years ago, histone deacetylases (HDACs), the versatile epigenetic regulators responsible for gene transcription via binding histones or non-histone substrates, have grabbed considerable attention in drug discovery. There are also substantial evidences supporting that aberrant expressions and/activities of HDAC isoforms are reported in epilepsy and HDAC inhibitors (HDACi) have been successfully utilized for therapeutic purposes in this condition. However, the specific mechanisms underlying the role of HDACs in epileptic progression have not been fully understood. Herein, we reviewed the basic information of HDACs, summarized the recent findings associated with the roles of diverse HDAC subunits in epilepsy and discussed the potential regulatory mechanisms by which HDACs affected the development of epilepsy. Additionally, we also provided a brief discussion on the potential of HDACs as promising therapeutic targets for epilepsy treatment, serving as a valuable reference for basic study and clinical translation in epilepsy field.

Topical histone deacetylase inhibitor remetinostat improves IMQ-induced psoriatic dermatitis via suppressing dendritic cell maturation and keratinocyte differentiation and inflammation

Psoriasis is a chronic inflammatory skin disease characterized by excessive proliferation of keratinocytes and infiltration of immune cells. Although psoriasis has entered the era of biological treatment, there is still a need to explore more effective therapeutic targets and drugs due to the presence of resistance and adverse reactions to biologics. Remetinostat, an HDAC inhibitor, can maintain its potency within the skin with minimal systemic effects, making it a promising topical medication for treating psoriasis. But its effectiveness in treating psoriasis has not been evaluated. In this study, the topical application of remetinostat significantly improved psoriasiform inflammation in an imiquimod-induced mice model by inhibiting CD86 expression of CD11C+I-A/I-E+ dendritic cells (DCs) in the skin. Moreover, remetinostat could dampen the maturation and activation of bone marrow-derived DCs in vitro, as well as the expression of psoriasis-related inflammatory mediators by keratinocytes. In addition, remetinostat could promote keratinocyte differentiation without affecting its proliferation. Our findings demonstrate that remetinostat improves psoriasis by inhibiting the maturation and activation of DCs and the differentiation and inflammation of keratinocytes, which may facilitate the potential application of remetinostat in anti-psoriasis therapy.

SAGCN: Using Graph Convolutional Network With Subgraph-Aware for circRNA-Drug Sensitivity Identification

Circular RNAs (circRNAs) play a significant role in cancer development and therapy resistance. There is substantial evidence indicating that the expression of circRNAs affects the sensitivity of cells to drugs. Identifying circRNAs-drug sensitivity association (CDA) is helpful for disease treatment and drug discovery. However, the identification of CDA through conventional biological experiments is both time-consuming and costly. Therefore, it is urgent to develop computational methods to predict CDA. In this study, we propose a new computational method, the subgraph-aware graph convolutional network (SAGCN), for predicting CDA. SAGCN first constructs a heterogeneous network composed of circRNA similarity network, drug similarity network, and circRNA-drug bipartite network. Then, a subgraph extractor is proposed to learn the latent subgraph structure of the heterogeneous network using a graph convolutional network. The extractor can capture 1-hop and 2-hop information and then a fusing attention mechanism is designed to integrate them adaptively. Simultaneously, a novel subgraph-aware attention mechanism is proposed to detect intrinsic subgraph structure. The final node feature representation is obtained to make the CDA prediction. Experimental results demonstrate that SAGCN obtained an average AUC of 0.9120 and AUPR of 0.8693, exceeding the performance of the most advanced models under 10-fold cross-validation. Case studies have demonstrated the potential of SAGCN in identifying associations between circRNA and drug sensitivity.

SIN3B Loss Heats up Cold Tumor Microenvironment to Boost Immunotherapy in Pancreatic Cancer

Despite progress significant advances in immunotherapy for some solid tumors, pancreatic ductal adenocarcinoma (PDAC) remains unresponsive poorly responsive to such interventions, largely due to its highly immunosuppressive tumor microenvironment (TME) with limited CD8+ T cell infiltration. This study explores the role of the epigenetic factor Sin3B in the PDAC TME. Using murine PDAC models, we found that tumor cell-intrinsic Sin3B loss reshapes the TME, increasing CD8+ T cell infiltration and cytotoxicity, thus impeding tumor progression and enhancing sensitivity to anti-PD1 treatment. Sin3B-deficient tumor cells exhibited amplified CXCL9/10 secretion in response to Interferon-gamma (IFNγ), creating a positive feedback loop via the CXCL9/10-CXCR3 axis, thereby intensifying the anti-tumor immune response against PDAC. Mechanistically, extensive epigenetic regulation is uncovered by Sin3B loss, particularly enhanced H3K27Ac distribution on genes related to immune responses in PDAC cells. Consistent with the murine model findings, analysis of human PDAC samples revealed a significant inverse correlation between SIN3B levels and both CD8+ T cell infiltration and CXCL9/10 expression. Notebly, PDAC patients with lower SIN3B expression showed a more favorable response to anti-PD1 therapy. The findings suggest that targeting SIN3B can enhance cytotoxic T cell infiltration into the tumor site and improve immunotherapy efficacy in PDAC, offering potential avenues for therapeutic biomarker or target in this challenging disease.

Design, synthesis, and biological activity evaluation of novel HDAC3 selective inhibitors for combination with Venetoclax against acute myeloid leukemia

Histone deacetylases (HDACs) are highly attractive targets in the drug development process, and the development of subtype-selective HDAC inhibitors is the research direction for HDAC inhibitors. As an important member of the HDAC family, HDAC3 has been found to be closely related to the pathological progression of many diseases due to its abnormal expression. In previous studies, we discovered compound 13a, which has potent inhibitory activity against HDAC1, 2, and 3. In this work, we improved the HDAC3 isotype selectivity of 13a, and obtained compound 9c through rational drug design. 9c shows a selectivity of 71 fold for HDAC3 over HDAC1 and can significantly inhibit the proliferation activity of MV4-11 cells in vitro. Furthermore, when combined with Venetoclax, 9c can effectively induce apoptosis in MV4-11 cells in vitro and reduce the expression of anti-apoptotic proteins, the development of HDAC3 selective inhibitors may serve as a potential lead compound to reverse Venetoclax resistance.

Heterocycles-Containing HDAC Inhibitors Active in Cancer: An Overview of the Last Fifteen Years

Cancer is one of the primary causes of mortality worldwide. Despite nowadays are numerous therapeutic treatments to fight tumor progression, it is still challenging to completely overcome it. It is known that Histone Deacetylases (HDACs), epigenetic enzymes that remove acetyl groups from lysines on histone's tails, are overexpressed in various types of cancer, and their inhibition represents a valid therapeutic strategy. To date, some HDAC inhibitors have achieved FDA approval. Nevertheless, several other potential drug candidates have been developed. This review aims primarily to be comprehensive of the studies done so far regarding HDAC inhibitors bearing heterocyclic rings since their therapeutic potential is well known and has gained increasing interest in recent years. Hence, inserting heterocyclic moieties in the HDAC-inhibiting scaffold can be a valuable strategy to provide potent and/or selective compounds. Here, in addition to summarizing the properties of novel heterocyclic HDAC inhibiting compounds, we also provide ideas for developing new, more potent, and selective compounds for treating cancer.

Advances in dual-targeting inhibitors of HDAC6 for cancer treatment

Histone Deacetylase 6 (HDAC6) is an essential regulator of histone acetylation processes, exerting influence on a multitude of cellular functions such as cell motility, endocytosis, autophagy, apoptosis, and protein trafficking through its deacetylation activity. The significant implications of HDAC6 in diseases such as cancer, neurodegenerative disorders, and immune disorders have motivated extensive investigation into the development of specific inhibitors targeting this enzyme for therapeutic purposes. Single targeting drugs carry the risk of inducing drug resistance, thus prompting exploration of dual targeting therapy which offers the potential to impact multiple signaling pathways simultaneously, thereby lowering the likelihood of resistance development. While pharmacological studies have exhibited promise in combined therapy involving HDAC6, challenges related to potential drug interactions exist. In response to these challenges, researchers are investigating HDAC6 hybrid molecules which enable the concomitant targeting of HDAC6 and other key proteins, thus enhancing treatment efficacy while mitigating side effects and reducing the risk of resistance compared to traditional combination therapies. The published design strategies for dual targeting inhibitors of HDAC6 are summarized and discussed in this review. This will provide some valuable insights into more novel HDAC6 dual targeting inhibitors to meet the urgent need for innovative therapies in oncology and other related fields.

Regulatory RNAs: role as scaffolds assembling protein complexes and their epigenetic deregulation

Recently, new data have been added to the interaction between non-coding RNAs (ncRNAs) and epigenetic machinery. Epigenetics includes enzymes involved in DNA methylation, histone modifications, and RNA modifications, and mechanisms underlying chromatin structure, repressive states, and active states operating in transcription. The main focus is on long ncRNAs (lncRNAs) acting as scaffolds to assemble protein complexes. This review does not cover RNA's role in sponging microRNAs, or decoy functions. Several lncRNAs were shown to regulate chromatin activation and repression by interacting with Polycomb repressive complexes and mixed-lineage leukemia (MLL) activating complexes. Various groups reported on enhancer of zeste homolog 2 (EZH2) interactions with regulatory RNAs. Knowledge of the function of these complexes opens the perspective to develop new therapeutics for cancer treatment. Lastly, the interplay between lncRNAs and epitranscriptomic modifications in cancers paves the way for new targets in cancer therapy. The approach to inhibit lncRNAs interaction with protein complexes and perspective to regulate epitrascriptomics-regulated RNAs may bring new compounds as therapeuticals in various types of cancer.

A Multi-Omics Analysis of an Exhausted T Cells' Molecular Signature in Pan-Cancer

T cells are essential tumor suppressors in cancer immunology, but their dysfunction induced by cancer cells can result in T cell exhaustion. Exhausted T cells (Tex) significantly influence the tumor immune environment, and thus, there is a need for their thorough investigation across different types of cancer. Here, we address the role of Tex cells in pan-cancer, focusing on the expression, mutations, methylation, immune infiltration, and drug sensitivity of a molecular signature comprising of the genes HAVCR2, CXCL13, LAG3, LAYN, TIGIT, and PDCD1across multiple cancer types, using bioinformatics analysis of TCGA data. Our analysis revealed that the Tex signature genes are differentially expressed across 14 cancer types, being correlated with patient survival outcomes, with distinct survival trends. Pathway analysis indicated that the Tex genes influence key cancer-related pathways, such as apoptosis, EMT, and DNA damage pathways. Immune infiltration analysis highlighted a positive correlation between Tex gene expression and immune cell infiltration in bladder cancer, while mutations in these genes were associated with specific immune cell enrichments in UCEC and SKCM. CNVs in Tex genes were widespread across cancers. We also highlight high LAYN methylation in most tumors and a negative correlation between methylation levels and immune cell infiltration in various cancers. Drug sensitivity analysis identified numerous correlations, with CXCL13 and HAVCR2 expressions influencing sensitivity to several drugs, including Apitolisib, Belinostat, and Docetaxel. Overall, these findings highlight the importance of reviving exhausted T cells to enhance the treatment efficacy to significantly boost anti-tumor immunity and achieve better clinical outcomes.

Complete hematologic response in a patient with multiple pretreated angioimmunoblastic T-cell lymphoma after belinostat therapy followed by allogeneic stem cell transplantation: A case report

Key Clinical Message

Belinostat therapy followed by hematopoietic stem cell transplantation is a promising salvage strategy for heavily pretreated patients with peripheral T-cell lymphoma.

Abstract

Effective treatments for peripheral T-cell lymphoma in the relapsed and refractory (r/r) setting are limited. However, with the development and approval of innovative therapies, effective therapeutic options are becoming available for this patient population. This case report describes the treatment course of a patient with multiple r/r nodal follicular T-helper cell lymphoma of angioimmunoblastic type. Treatment with the histone deacetylase inhibitor belinostat as bridging, enabled allogeneic stem cell transplantation and resulted in a durable complete hematologic response for at least 21 months post-transplantation.

Design, synthesis and neuroprotective biological evaluation of novel HDAC6 inhibitors incorporating benzothiadiazinyl systems as cap groups

Histone deacetylase 6 (HDAC6), as the key regulatory enzyme, plays an important role in the development of the nervous system. More and more studies indicate that HDAC6 has become a promising therapeutic target for CNS diseases. Herein we designed and synthesized a series of novel HDAC6 inhibitors with benzothiadiazinyl systems as cap groups and evaluated their activity in vitro and in vivo. Among them, compound 3 exhibited superior selective inhibitory activity against HDAC6 (IC50 = 5.1 nM, about 30-fold selectivity over HDAC1). The results of docking showed that compound 3 can interact well with the key amino acid residues of HDAC6. Compound 3 showed lower cytotoxicity (20 μM to SH-SY5Y cells, inhibition rate = 25.75%) and better neuroprotective activity against L-glutamate-induced SH-SY5Y cell injury model in vitro. Meanwhile, compound 3 exhibited weak cardiotoxicity (10 μM hERG inhibition rate = 17.35%) and possess good druggability properties. Especially, compound 3 could significantly reduce cerebral infarction from 49.87% to 32.18%, and similar with butylphthalide in MCAO model, indicating potential clinical application prospects for alleviating ischemic stroke-induced brain infarction.

Enlightening epigenetics: optochemical tools illuminate the path

Optochemical tools have become potent instruments for understanding biological processes at the molecular level, and the past decade has witnessed their use in epigenetics and epitranscriptomics (also known as RNA epigenetics) for deciphering gene expression regulation. By using photoresponsive molecules such as photoswitches and photocages, researchers can achieve precise control over when and where specific events occur. Therefore, these are invaluable for studying both histone and nucleotide modifications and exploring disease-related mechanisms. We systematically report and assess current examples in the field, and identify open challenges and future directions. These outstanding proof-of-concept investigations will inspire other chemical biologists to participate in these emerging fields given the potential of photochromic molecules in research and biomedicine.

Design, synthesis and activity evaluation of arctigenin derivatives with HDAC inhibition activity

Arctigenin, a natural product with diverse pharmacological activities, can inhibit cell proliferation and survival and has shown promising potential in cancer research. In this study, we designed a series of arctigenin derivatives with HDAC inhibitory activity based on the synergistic effects between HDAC inhibitors and arctigenin. Among them, compound B7 exhibited significantly higher antiproliferative activity in the MV411 cell line compared to the positive control, tucidinostat. Additionally, enzymatic activity testing was performed with compound B7. Further mechanistic studies indicated that compound B7 induced apoptosis through the Caspase-3 pathway in MV411 cells and enhanced histone acetylation levels in the MV411 cell line. These findings highlight the broad potential application of these arctigenin derivatives in cancer therapy.

Insight in Quinazoline-based HDAC Inhibitors as Anti-cancer Agents

Cancer remains a primary cause of death globally, and effective treatments are still limited. While chemotherapy has notably enhanced survival rates, it brings about numerous side effects. Consequently, the ongoing challenge persists in developing potent anti-cancer agents with minimal toxicity. The versatile nature of the quinazoline moiety has positioned it as a pivotal component in the development of various antitumor agents, showcasing its promising role in innovative cancer therapeutics. This concise review aims to reveal the potential of quinazolines in creating anticancer medications that target histone deacetylases (HDACs).

Inferring circRNA-drug sensitivity associations via dual hierarchical attention networks and multiple kernel fusion

Increasing evidence has shown that the expression of circular RNAs (circRNAs) can affect the drug sensitivity of cells and significantly influence drug efficacy. Therefore, research into the relationships between circRNAs and drugs can be of great significance in increasing the comprehension of circRNAs function, as well as contributing to the discovery of new drugs and the repurposing of existing drugs. However, it is time-consuming and costly to validate the function of circRNA with traditional medical research methods. Therefore, the development of efficient and accurate computational models that can assist in discovering the potential interactions between circRNAs and drugs is urgently needed. In this study, a novel method is proposed, called DHANMKF , that aims to predict potential circRNA-drug sensitivity interactions for further biomedical screening and validation. Firstly, multimodal networks were constructed by DHANMKF using multiple sources of information on circRNAs and drugs. Secondly, comprehensive intra-type and inter-type node representations were learned using bi-typed multi-relational heterogeneous graphs, which are attention-based encoders utilizing a hierarchical process. Thirdly, the multi-kernel fusion method was used to fuse intra-type embedding and inter-type embedding. Finally, the Dual Laplacian Regularized Least Squares method (DLapRLS) was used to predict the potential circRNA-drug sensitivity associations using the combined kernel in circRNA and drug spaces. Compared with the other methods, DHANMKF obtained the highest AUC value on two datasets. Code is available at https://github.com/cuntjx/DHANMKF .

The application of PROTAC in HDAC

Inducing protein degradation by proteolysis targeting chimera (PROTAC) has provided great opportunities for scientific research and industrial applications. Histone deacetylase (HDAC)-PROTAC has been widely developed since the first report of its ability to induce the degradation of SIRT2 in 2017. To date, ten of the eighteen HDACs (HDACs 1-8, HDAC10, and SIRT2) have been successfully targeted and degraded by HDAC-PROTACs. HDAC-PROTACs surpass traditional HDAC inhibitors in many aspects, such as higher selectivity, more potent antiproliferative activity, and the ability to disrupt the enzyme-independent functions of a multifunctional protein and overcome drug resistance. Rationally designing HDAC-PROTACs is a main challenge in development because slight variations in chemical structure can lead to drastic effects on the efficiency and selectivity of the degradation. In the future, HDAC-PROTACs can potentially be involved in clinical research with the support of the increased amount of in vivo data, pharmacokinetic evaluation, and pharmacological studies.

Antibody drug conjugates beyond cytotoxic payloads

For many years, antibody drug conjugates (ADC) have teased with the promise of targeted payload delivery to diseased cells, embracing the targeting of the antibody to which a cytotoxic payload is conjugated. During the past decade this promise has started to be realised with the approval of more than a dozen ADCs for the treatment of various cancers. Of these ADCs, brentuximab vedotin really laid the foundations of a template for a successful ADC with lysosomal payload release from a cleavable dipeptide linker, measured DAR by conjugation to the Cys-Cys interchain bonds of the antibody and a cytotoxic payload. Using this ADC design model oncology has now expanded their repertoire of payloads to include non-cytotoxic compounds. These new payload classes have their origins in prior medicinal chemistry programmes aiming to design selective oral small molecule drugs. While this may not have been achieved, the resulting compounds provide excellent starting points for ADC programmes with some compounds amenable to immediate linker attachment while for others extensive SAR and structural information offer invaluable design insights. Many of these new oncology payload classes are of interest to other therapeutic areas facilitating rapid access to drug-linkers for exploration as non-oncology ADCs. Other therapeutic areas have also pursued unique payload classes with glucocorticoid receptor modulators (GRM) being the most clinically advanced in immunology. Here, ADC payloads come full circle, as oncology is now investigating GRM payloads for the treatment of cancer. This chapter aims to cover all these new ADC approaches while describing the medicinal chemistry origins of the new non-cytotoxic payloads.

N-(2-Aminophenyl)-benzamide Inhibitors of Class I HDAC Enzymes with Antiproliferative and Antifibrotic Activity

Inhibitors of histone deacetylases (HDACs) have received special attention as novel anticancer agents. Among various types of synthetic inhibitors, benzamides constitute an important class, and one is an approved drug (chidamide). Here, we present a novel class of HDAC inhibitors containing the N-(2-aminophenyl)-benzamide functionality as the zinc-binding group linked to various cap groups, including the amino acids pyroglutamic acid and proline. We have identified benzamides that inhibit HADC1 and HDAC2 at nanomolar concentrations, with antiproliferative activity at micromolar concentrations against A549 and SF268 cancer cell lines. Docking studies shed light on the mode of binding of benzamide inhibitors to HDAC1, whereas cellular analysis revealed downregulated expression of EGFR mRNA and protein. Two benzamides were investigated in a mouse model of bleomycin-induced pulmonary fibrosis, and both showed efficacy on a preventative dosing schedule. N-(2-Aminophenyl)-benzamide inhibitors of class I HDACs might lead to new approaches for treating fibrotic disorders.

2-Substituted 1,5-benzothiazepine-based HDAC inhibitors exert anticancer activities on human solid and acute myeloid leukemia cell lines

Herein, we report the development of a new series of histone deacetylase inhibitors (HDACi) containing a 2-substituted 1,5-benzothiazepine scaffold. First, a virtual combinatorial library (∼1.6 × 103 items) was built according to a convenient synthetic route, and then it was submitted to molecular docking experiments on seven HDACs isoforms belonging to classes I and II. Integrated computational filters were used to select the most promising ones that were synthesized through an optimized approach, also amenable to generating both racemic and enantioenriched benzothiazepine-based derivatives. The obtained compounds showed potent HDAC inhibitory activity, especially those containing the sulphone moiety, endowed with IC50 in the nanomolar range. In addition, in vitro outcomes of our synthesized compounds demonstrated a cytotoxic effect on U937 and HCT116 cell lines and an arrest in the G2/M phase (13 ≤ IC50 ≤ 18 µM). Finally, Western blot analyses outlined the modulation of the histone acetyl markers such as H3K9/14, acetyl-tubulin, and the apoptotic indicator p21 in both cancer cell lines, disclosing a good HDAC inhibitor activity exerted by the designed items. Given the key role of HDACs in many cellular pathways, which makes these enzymes appealing and "hot" drug targets, our findings highlighted the importance of these 2-substituted 1,5-benzothiazepine-based compounds (both in the reduced and oxidized version) for the development of novel epidrugs.

Post-translational modifications of histones: Mechanisms, biological functions, and therapeutic targets

Histones are DNA-binding basic proteins found in chromosomes. After the histone translation, its amino tail undergoes various modifications, such as methylation, acetylation, phosphorylation, ubiquitination, malonylation, propionylation, butyrylation, crotonylation, and lactylation, which together constitute the "histone code." The relationship between their combination and biological function can be used as an important epigenetic marker. Methylation and demethylation of the same histone residue, acetylation and deacetylation, phosphorylation and dephosphorylation, and even methylation and acetylation between different histone residues cooperate or antagonize with each other, forming a complex network. Histone-modifying enzymes, which cause numerous histone codes, have become a hot topic in the research on cancer therapeutic targets. Therefore, a thorough understanding of the role of histone post-translational modifications (PTMs) in cell life activities is very important for preventing and treating human diseases. In this review, several most thoroughly studied and newly discovered histone PTMs are introduced. Furthermore, we focus on the histone-modifying enzymes with carcinogenic potential, their abnormal modification sites in various tumors, and multiple essential molecular regulation mechanism. Finally, we summarize the missing areas of the current research and point out the direction of future research. We hope to provide a comprehensive understanding and promote further research in this field.

Epigenetic targets in B- and T-cell lymphomas: latest developments

Non-Hodgkin's lymphomas (NHLs) comprise a diverse group of diseases, either of mature B-cell or of T-cell derivation, characterized by heterogeneous molecular features and clinical manifestations. While most of the patients are responsive to standard chemotherapy, immunotherapy, radiation and/or stem cell transplantation, relapsed and/or refractory cases still have a dismal outcome. Deep sequencing analysis have pointed out that epigenetic dysregulations, including mutations in epigenetic enzymes, such as chromatin modifiers and DNA methyltransferases (DNMTs), are prevalent in both B- cell and T-cell lymphomas. Accordingly, over the past decade, a large number of epigenetic-modifying agents have been developed and introduced into the clinical management of these entities, and a few specific inhibitors have already been approved for clinical use. Here we summarize the main epigenetic alterations described in B- and T-NHL, that further supported the clinical development of a selected set of epidrugs in determined diseases, including inhibitors of DNMTs, histone deacetylases (HDACs), and extra-terminal domain proteins (bromodomain and extra-terminal motif; BETs). Finally, we highlight the most promising future directions of research in this area, explaining how bioinformatics approaches can help to identify new epigenetic targets in B- and T-cell lymphoid neoplasms.

HDAC inhibitors enhance the anti-tumor effect of immunotherapies in hepatocellular carcinoma

Hepatocellular carcinoma (HCC), the most common liver malignancy with a poor prognosis and increasing incidence, remains a serious health problem worldwide. Immunotherapy has been described as one of the ideal ways to treat HCC and is transforming patient management. However, the occurrence of immunotherapy resistance still prevents some patients from benefiting from current immunotherapies. Recent studies have shown that histone deacetylase inhibitors (HDACis) can enhance the efficacy of immunotherapy in a variety of tumors, including HCC. In this review, we present current knowledge and recent advances in immunotherapy-based and HDACi-based therapies for HCC. We highlight the fundamental dynamics of synergies between immunotherapies and HDACis, further detailing current efforts to translate this knowledge into clinical benefits. In addition, we explored the possibility of nano-based drug delivery system (NDDS) as a novel strategy to enhance HCC treatment.

An Update of Epigenetic Drugs for the Treatment of Cancers and Brain Diseases: A Comprehensive Review

Epigenetics has long been recognized as a significant field in biology and is defined as the investigation of any alteration in gene expression patterns that is not attributed to changes in the DNA sequences. Epigenetic marks, including histone modifications, non-coding RNAs, and DNA methylation, play crucial roles in gene regulation. Numerous studies in humans have been carried out on single-nucleotide resolution of DNA methylation, the CpG island, new histone modifications, and genome-wide nucleosome positioning. These studies indicate that epigenetic mutations and aberrant placement of these epigenetic marks play a critical role in causing the disease. Consequently, significant development has occurred in biomedical research in identifying epigenetic mechanisms, their interactions, and changes in health and disease conditions. The purpose of this review article is to provide comprehensive information about the different types of diseases caused by alterations in epigenetic factors such as DNA methylation and histone acetylation or methylation. Recent studies reported that epigenetics could influence the evolution of human cancer via aberrant methylation of gene promoter regions, which is associated with reduced gene function. Furthermore, DNA methyltransferases (DNMTs) in the DNA methylation process as well as histone acetyltransferases (HATs)/histone deacetylases (HDACs) and histone methyltransferases (HMTs)/demethylases (HDMs) in histone modifications play important roles both in the catalysis and inhibition of target gene transcription and in many other DNA processes such as repair, replication, and recombination. Dysfunction in these enzymes leads to epigenetic disorders and, as a result, various diseases such as cancers and brain diseases. Consequently, the knowledge of how to modify aberrant DNA methylation as well as aberrant histone acetylation or methylation via inhibitors by using epigenetic drugs can be a suitable therapeutic approach for a number of diseases. Using the synergistic effects of DNA methylation and histone modification inhibitors, it is hoped that many epigenetic defects will be treated in the future. Numerous studies have demonstrated a link between epigenetic marks and their effects on brain and cancer diseases. Designing appropriate drugs could provide novel strategies for the management of these diseases in the near future.

Therapeutic targeting of DNA damage repair pathways guided by homologous recombination deficiency scoring in ovarian cancers

The susceptibility of cells to DNA damage and their DNA repair ability are crucial for cancer therapy. Homologous recombination is one of the major repairing mechanisms for DNA double-strand breaks. Approximately half of ovarian cancer (OvCa) cells harbor homologous recombination deficiency (HRD). Considering that HRD is a major hallmark of OvCas, scholars proposed HRD scoring to evaluate the HRD degree and guide the choice of therapeutic strategies for OvCas. In the last decade, synthetic lethal strategy by targeting poly (ADP-ribose) polymerase (PARP) in HR-deficient OvCas has attracted considerable attention in view of its favorable clinical effort. We therefore suggested that the uses of other DNA damage/repair-targeted drugs in HR-deficient OvCas might also offer better clinical outcome. Here, we reviewed the current small molecule compounds that targeted DNA damage/repair pathways and discussed the HRD scoring system to guide their clinical uses.

Emerging Epigenetic-Based Nanotechnology for Cancer Therapy: Modulating the Tumor Microenvironment

Dysregulated epigenetic modifications dynamically drive the abnormal transcription process to affect the tumor microenvironment; thus, promoting cancer progression, drug resistance, and metastasis. Nowadays, therapies targeting epigenetic dysregulation of tumor cells and immune cells in the tumor microenvironment appear to be promising adjuncts to other cancer therapies. However, the clinical results of combination therapies containing epigenetic agents are disappointing due to systemic toxicities and limited curative effects. Here, the role of epigenetic processes, including DNA methylation, post-translational modification of histones, and noncoding RNAs is discussed, followed by detailed descriptions of epigenetic regulation of the tumor microenvironment, as well as the application of epigenetic modulators in antitumor therapy, with an emphasis on the epigenetic-based advanced drug delivery system in targeting the tumor microenvironment.

Novel pyridine-containing histone deacetylase inhibitors strongly arrest proliferation, induce apoptosis and modulate miRNAs in cancer cells

After over 30 years of research, the development of HDAC inhibitors led to five FDA/Chinese FDA-approved drugs and many others under clinical or preclinical investigation to treat cancer and non-cancer diseases. Herein, based on our recent development of pyridine-based isomers as HDAC inhibitors, we report a series of novel 5-acylamino-2-pyridylacrylic- and -picolinic hydroxamates and 2'-aminoanilides 5-8 as anticancer agents. The hydroxamate 5d proved to be quite HDAC3/6-selective exhibiting IC₅₀ values of 80 and 11 nM, respectively, whereas the congener 5e behaved as inhibitor of HDAC1-3, -6, -8, and -10 (class I/IIb-selective inhibitor) at nanomolar level. Compound 5e provided a huge antiproliferative activity (nanomolar IC₅₀ values) against both haematological and solid cancer cell lines. In leukaemia U937 cells, the hydroxamate 5d and the 2'-aminoanilide 8f induced remarkable cell death after 48 h, with 76% and 100% pre-G1 phase arrest, respectively, showing a stronger effect with respect to SAHA and MS-275 used as reference compounds. In U937 cells, the highest dose- and time-dependent cytodifferentiation was obtained by the 2'-aminoanilide 8d (up to 35% of CD11c positive/propidium iodide negative cells at 5 μM for 48 h). The same 8d and the hydroxamates 5d and 5e were the most effective in inducing p21 protein expression in the same cell line. Mechanistically, 5d, 5e, 8d and 8f increased mRNA expression of p21, BAX and BAK, downregulated cyclin D1 and BCL-2 and modulated pro- and anti-apoptotic microRNAs towards apoptosis induction. Finally, 5e strongly arrested proliferation in nine different haematological cancer cell lines, with dual-digit nanomolar potency towards MV4-11, Kasumi-1, and NB4, being more potent than mocetinostat, used as reference drug.

Histone Deacetylase Functions in Gastric Cancer: Therapeutic Target?

Gastric cancer (GC) is one of the most aggressive cancers. Therapeutic treatments are based on surgery combined with chemotherapy using a combination of platinum-based agents. However, at metastatic stages of the disease, survival is extremely low due to late diagnosis and resistance mechanisms to chemotherapies. The development of new classifications has not yet identified new prognostic markers for clinical use. The studies of epigenetic processes highlighted the implication of histone acetylation status, regulated by histone acetyltransferases (HATs) and by histone deacetylases (HDACs), in cancer development. In this way, inhibitors of HDACs (HDACis) have been developed and some of them have already been clinically approved to treat T-cell lymphoma and multiple myeloma. In this review, we summarize the regulations and functions of eighteen HDACs in GC, describing their known targets, involved cellular processes, associated clinicopathological features, and impact on survival of patients. Additionally, we resume the in vitro, pre-clinical, and clinical trials of four HDACis approved by Food and Drug Administration (FDA) in cancers in the context of GC.

First-in-Class Hydrazide-Based HDAC6 Selective Inhibitor with Potent Oral Anti-Inflammatory Activity by Attenuating NLRP3 Inflammasome Activation

In this study, we report the first highly selective HDAC6 inhibitor with hydrazide as the zinc-binding group (ZBG), which displays superior pharmacokinetic properties to the current hydroxamic acid inhibitors. Structure-activity relationship study reveals that ethyl group substituent hydrazide-based ZBG and cap group with more substantial rigidity and larger volume increase the HDAC6 selectivity of designed compounds. Representative inhibitor 35m exhibits potent HDAC6 inhibitory activity with an IC₅₀ value of 0.019 μM. To our surprise, 35m establishes significant improvement in the pharmacokinetic property with much higher AUC_0-inf (10292 ng·h/mL) and oral bioavailability (93.4%) than hydroximic acid-based HDAC6 inhibitors Tubastatin A and ACY-1215. Low-dose 35m remarkably decreases LPS-induced IL-1β release both in vitro and in vivo by blocking the activation of NLRP3, indicating that 35m can be a potential orally active therapeutic agent for the treatment of NLRP3-related diseases.

Anti-multiple myeloma potential of resynthesized belinostat derivatives: an experimental study on cytotoxic activity, drug combination, and docking studies

Multiple myeloma is a deadly cancer that is a complex and multifactorial disease. In the present study, 12 belinostat derivatives (four resynthesized and eight new), HDAC inhibitors, were resynthesized via either Knoevenagel condensation, or Wittig reaction, or Heck reaction. Then an evaluation of the antiproliferative activities against myeloma cells MOPC-315 was carried out. Amongst them, compound 7f was the most bioactive compound with an IC50 of 0.090 ± 0.016 μM, being 3.5-fold more potent than the reference belinostat (IC50 = 0.318 ± 0.049 μM). Furthermore, we also confirmed the inhibitory activity of 7f in a cellular model. Additionally, we found that the inhibitory activity of 7f against histone deacetylase 6 catalytic activity (HDAC6) is more potent than that of belinostat. Finally, we observed the strong synergistic interaction between the derivative 7f and the proteasome bortezomib inhibitor (CI = 0.26), while belinostat and bortezomib showed synergism with a CI value of 0.36. Taken together, the above results suggest that 7f is a promising HDAC inhibitor deserving further investigation.

Glioblastoma: Current Status, Emerging Targets, and Recent Advances

Glioblastoma (GBM) is a highly malignant brain tumor characterized by a heterogeneous population of genetically unstable and highly infiltrative cells that are resistant to chemotherapy. Although substantial efforts have been invested in the field of anti-GBM drug discovery in the past decade, success has primarily been confined to the preclinical level, and clinical studies have often been hampered due to efficacy-, selectivity-, or physicochemical property-related issues. Thus, expansion of the list of molecular targets coupled with a pragmatic design of new small-molecule inhibitors with central nervous system (CNS)-penetrating ability is required to steer the wheels of anti-GBM drug discovery endeavors. This Perspective presents various aspects of drug discovery (challenges in GBM drug discovery and delivery, therapeutic targets, and agents under clinical investigation). The comprehensively covered sections include the recent medicinal chemistry campaigns embarked upon to validate the potential of numerous enzymes/proteins/receptors as therapeutic targets in GBM.

Histone Deacetylases as Epigenetic Targets for Treating Parkinson's Disease

Parkinson's disease (PD) is a chronic progressive neurodegenerative disease that is increasingly becoming a global threat to the health and life of the elderly worldwide. Although there are some drugs clinically available for treating PD, these treatments can only alleviate the symptoms of PD patients but cannot completely cure the disease. Therefore, exploring other potential mechanisms to develop more effective treatments that can modify the course of PD is still highly desirable. Over the last two decades, histone deacetylases, as an important group of epigenetic targets, have attracted much attention in drug discovery. This review focused on the current knowledge about histone deacetylases involved in PD pathophysiology and their inhibitors used in PD studies. Further perspectives related to small molecules that can inhibit or degrade histone deacetylases to treat PD were also discussed.

FDA-Approved Drugs for Hematological Malignancies-The Last Decade Review

Simple Summary

Hematological malignancies are diseases involving the abnormal production of blood cells. The aim of the study is to collect comprehensive information on new drugs used in the treatment of blood cancers which have introduced into therapy in the last decade. The approved drugs were analyzed for their structures and their biological activity mechanisms.

Abstract

Hematological malignancies, also referred to as blood cancers, are a group of diseases involving abnormal cell growth and persisting in the blood, lymph nodes, or bone marrow. The development of new targeted therapies including small molecule inhibitors, monoclonal antibodies, bispecific T cell engagers, antibody-drug conjugates, recombinant immunotoxins, and, finally, Chimeric Antigen Receptor T (CAR-T) cells has improved the clinical outcomes for blood cancers. In this review, we summarized 52 drugs that were divided into small molecule and macromolecule agents, approved by the Food and Drug Administration (FDA) in the period between 2011 and 2021 for the treatment of hematological malignancies. Forty of them have also been approved by the European Medicines Agency (EMA). We analyzed the FDA-approved drugs by investigating both their structures and mechanisms of action. It should be emphasized that the number of targeted drugs was significantly higher (46 drugs) than chemotherapy agents (6 drugs). We highlight recent advances in the design of drugs that are used to treat hematological malignancies, which make them more effective and less toxic.

Potent Hydrazide-Based HDAC Inhibitors with a Superior Pharmacokinetic Profile for Efficient Treatment of Acute Myeloid Leukemia In Vivo

As "Michael acceptors" may induce promiscuous responses in mammalian cells by reacting with various proteins, we modified the cinnamamide of our previous hydrazide-based HDAC inhibitors (HDACIs) to deactivate the Michael reaction. Representative compound 11h is 2-5 times more potent than lead compound 17 in both HDAC inhibitory activity (IC₅₀ = 0.43-3.01 nM) and cell-based antitumor assay (IC₅₀ = 19.23-61.04 nM). The breakthrough in the pharmacokinetic profile of 11h (oral bioavailability: 112%) makes it a lead-in-class oral active agent, validated in the in vivo anti-AML study (4 mg/kg p.o., TGI = 78.9%). Accumulated AcHH3 and AcHH4 levels in tumor tissue directly correlate with the in vivo efficacy, as panobinostat with lower AcHH3 and AcHH4 levels than 11h displays limited activity. To the best of our knowledge, this work contributes the first report of in vivo antitumor activity of hydrazide-based HDACIs. The outstanding pharmacokinetic/pharmacodynamic and antitumor activity of 11h could potentially extend the clinical application of current HDACIs.

Advances in the Design and Development of PROTAC-mediated HDAC degradation

Due to developments in modern chemistry, previously undruggable targets are becoming druggable thanks to selective degradation using the ubiquitin-proteasomal degradation system. PROteolysis TArgeting Chimeras (PROTACs) are heterobifunctional molecules designed specifically to degrade target proteins (protein of interest, POI). They are of significant interest to industry and academia as they are highly specific and can target previously undruggable target proteins from transcription factors to enzymes. More than 15 degraders are expected to be evaluated in clinical trials by the end of 2021. Herein, we describe recent advances in the design and development of PROTAC-mediated degradation of histone deacetylases (HDACs). PROTAC-mediated degradation of HDACs can offer some significant advantages over direct inhibition, such as the use of substoichiometric doses and the potential to disrupt enzyme-independent HDAC function. Herein, we discuss the potential implications of the degradation of HDACs with HDAC knockout studies and the selection of HDAC inhibitors and E3 ligase ligands for the design of the PROTACs. The potential utility of HDAC PROTACs in various disease pathologies from cancer to inflammation to neurodegeneration is driving the interest in this field.

The contributory roles of histone deacetylases (HDACs) in hematopoiesis regulation and possibilities for pharmacologic interventions in hematologic malignancies

Although the definitive role of epigenetic modulations in a wide range of hematologic malignancies, spanning from leukemia to lymphoma and multiple myeloma, has been evidenced, few articles reviewed the task. Given the high accessibility of histone deacetylase (HDACs) to necessary transcription factors involved in hematopoiesis, this review aims to outline physiologic impacts of these enzymes in normal hematopoiesis, and also to outline the original data obtained from international research laboratories on their regulatory role in the differentiation and maturation of different hematopoietic lineages. Questions on how aberrant expression of HDACs contributes to the formation of hematologic malignancies are also responded, because these classes of enzymes have a respectable share in the development, progression, and recurrence of leukemia, lymphoma, and multiple myeloma. The last section provides a special focus on the therapeutic perspectiveof HDACs inhibitors, either as single agents or in a combined-modal strategy, in these neoplasms. In conclusion, optimizing the dose and the design of more patient-tailored inhibitors, while maintaining low toxicity against normal cells, will help improve clinical outcomes of HDAC inhibitors in hematologic malignancies.

Discovery of a novel HDACi structure that inhibits the proliferation of ovarian cancer cells in vivo and in vitro

Histone deacetylases (HDACs) exhibit increased expression in cancer and promote oncogenesis via the acetylation of or interactions with key transcriptional regulators. HDAC inhibitors (HDACis) decrease HDAC activity to selectively inhibit the occurrence and development of tumors. Our study screened and obtained a new HDACi structure. In vitro experiments have showed that among the leads, Z31216525 significantly inhibited the proliferation and induced the apoptosis of epithelial ovarian cancer (EOC) cells. In vivo experiments demonstrated that compared to the control, Z31216525 significantly inhibited tumor growth and showed very low toxicity. Further mechanistic studies revealed that Z31216525 may exert an antitumor effect by inhibiting the expression of the c-Myc gene. Collectively, our studies identified a novel HDACi that is expected to become a new potential therapeutic drug for EOC and has important value for the design of new HDACi structures.

Hydralazine and Panobinostat Attenuate Malignant Properties of Prostate Cancer Cell Lines

Among the well-established alterations contributing to prostate cancer (PCa) pathogenesis, epigenetics is an important player in its development and aggressive disease state. Moreover, since no curative therapies are available for advanced stage disease, there is an urgent need for novel therapeutic strategies targeting this subset of patients. Thus, we aimed to evaluate the combined antineoplastic effects of DNA methylation inhibitor hydralazine and histone deacetylase inhibitors panobinostat and valproic acid in several prostate cell lines. The effect of these drugs was assessed in four PCa (LNCaP, 22Rv1, DU145 and PC-3) cell lines, as well as in non-malignant epithelial (RWPE-1) and stromal (WPMY-1) cell lines, using several assays to evaluate cell viability, apoptosis, proliferation, DNA damage and clonogenic potential. We found that exposure to each epidrug separately reduced viability of all PCa cells in a dose-dependent manner and that combined treatments led to synergic growth inhibitory effects, impacting also on colony formation, invasion, apoptotic and proliferation rates. Interestingly, antitumoral effects of combined treatment were particularly expressive in DU145 cells. We concluded that hydralazine and panobinostat attenuate malignant properties of PCa cells, constituting a potential therapeutic tool to counteract PCa progression.

Dissecting Histone Deacetylase 3 in Multiple Disease Conditions: Selective Inhibition as a Promising Therapeutic Strategy

The acetylation of histone and non-histone proteins has been implicated in several disease states. Modulation of such epigenetic modifications has therefore made histone deacetylases (HDACs) important drug targets. HDAC3, among various class I HDACs, has been signified as a potentially validated target in multiple diseases, namely, cancer, neurodegenerative diseases, diabetes, obesity, cardiovascular disorders, autoimmune diseases, inflammatory diseases, parasitic infections, and HIV. However, only a handful of HDAC3-selective inhibitors have been reported in spite of continuous efforts in design and development of HDAC3-selective inhibitors. In this Perspective, the roles of HDAC3 in various diseases as well as numerous potent and HDAC3-selective inhibitors have been discussed in detail. It will surely open up a new vista in the discovery of newer, more effective, and more selective HDAC3 inhibitors.