Development of Tetrahydroisoquinoline-Based Hydroxamic Acid Derivatives: Potent Histone Deacetylase Inhibitors with Marked in Vitro and in Vivo Antitumor Activities

Tetrahydroisoquinolines - an updated patent review for cancer treatment (2016 - present)

INTRODUCTION

Cancer is a prominent cause of death globally, triggered by both non-genetic and genetic alterations in genes influenced by various environmental factors. The tetrahydroisoquinoline (THIQ), specifically 1,2,3,4-tetrahydroisoquinoline serves as fundamental element in various alkaloids, prevalent in proximity to quinoline and indole alkaloids.

AREA COVERED

In this review, the therapeutic applications of THIQ derivatives as an anticancer agent from 2016 to 2024 have been examined. The patents were gathered through comprehensive searches of the Espacenet, Google patent, WIPO, and Sci Finder databases. The therapeutic areas encompassed in the patents include numerous targets of cancer.

EXPERT OPINION

THIQ analogues play a crucial role in medicinal chemistry, with many being integral to pharmacological processes and clinical trials. Numerous THIQ compounds have been synthesized for therapeutic purposes, notably in cancer treatment. They show great promise for developing anticancer drugs, demonstrating strong affinity and efficacy against various cancer targets. The creation of multi-target ligands is a compelling avenue for THIQ-based anticancer drug discovery.

Unveiling critical structural features for effective HDAC8 inhibition: a comprehensive study using quantitative read-across structure-activity relationship (q-RASAR) and pharmacophore modeling

Histone deacetylases constitute a group of enzymes that participate in several biological processes. Notably, inhibiting HDAC8 has become a therapeutic strategy for various diseases. The current inhibitors for HDAC8 lack selectivity and target multiple HDACs. Consequently, there is a growing recognition of the need for selective HDAC8 inhibitors to enhance the effectiveness of therapeutic interventions. In our current study, we have utilized a multi-faceted approach, including Quantitative Structure-Activity Relationship (QSAR) combined with Quantitative Read-Across Structure-Activity Relationship (q-RASAR) modeling, pharmacophore mapping, molecular docking, and molecular dynamics (MD) simulations. The developed q-RASAR model has a high statistical significance and predictive ability (Q2F1:0.778, Q2F2:0.775). The contributions of important descriptors are discussed in detail to gain insight into the crucial structural features in HDAC8 inhibition. The best pharmacophore hypothesis exhibits a high regression coefficient (0.969) and a low root mean square deviation (0.944), highlighting the importance of correctly orienting hydrogen bond acceptor (HBA), ring aromatic (RA), and zinc-binding group (ZBG) features in designing potent HDAC8 inhibitors. To confirm the results of q-RASAR and pharmacophore mapping, molecular docking analysis of the five potent compounds (44, 54, 82, 102, and 118) was performed to gain further insights into these structural features crucial for interaction with the HDAC8 enzyme. Lastly, MD simulation studies of the most active compound (54, mapped correctly with the pharmacophore hypothesis) and the least active compound (34, mapped poorly with the pharmacophore hypothesis) were carried out to validate the observations of the studies above. This study not only refines our understanding of essential structural features for HDAC8 inhibition but also provides a robust framework for the rational design of novel selective HDAC8 inhibitors which may offer insights to medicinal chemists and researchers engaged in the development of HDAC8-targeted therapeutics.

A Therapeutic Perspective of HDAC8 in Different Diseases: An Overview of Selective Inhibitors

Histone deacetylases (HDACs) are epigenetic enzymes which participate in transcriptional repression and chromatin condensation mechanisms by removing the acetyl moiety from acetylated ε-amino group of histone lysines and other non-histone proteins. In recent years, HDAC8, a class I HDAC, has emerged as a promising target for different disorders, including X-linked intellectual disability, fibrotic diseases, cancer, and various neuropathological conditions. Selective HDAC8 targeting is required to limit side effects deriving from the treatment with pan-HDAC inhibitors (HDACis); thus, many endeavours have focused on the development of selective HDAC8is. In addition, polypharmacological approaches have been explored to achieve a synergistic action on multi-factorial diseases or to enhance the drug efficacy. In this frame, proteolysis-targeting chimeras (PROTACs) might be regarded as a dual-targeting approach for attaining HDAC8 proteasomal degradation. This review highlights the most relevant and recent advances relative to HDAC8 validation in various diseases, providing a snapshot of the current selective HDAC8is, with a focus on polyfunctional modulators.

Quinazoline Based HDAC Dual Inhibitors as Potential Anti-Cancer Agents

Cancer is the most devastating disease and second leading cause of death around the world. Despite scientific advancements in the diagnosis and treatment of cancer which can include targeted therapy, chemotherapy, endocrine therapy, immunotherapy, radiotherapy and surgery in some cases, cancer cells appear to outsmart and evade almost any method of treatment by developing drug resistance. Quinazolines are the most versatile, ubiquitous and privileged nitrogen bearing heterocyclic compounds with a wide array of biological and pharmacological applications. Most of the anti-cancer agents featuring quinazoline pharmacophore have shown promising therapeutic activity. Therefore, extensive research is underway to explore the potential of these privileged scaffolds. In this context, a molecular hybridization approach to develop hybrid drugs has become a popular tool in the field of drug discovery, especially after witnessing the successful results during the past decade. Histone deacetylases (HDACs) have emerged as an important anti-cancer target in the recent years given its role in cellular growth, gene regulation, and metabolism. Dual inhibitors, especially based on HDAC in particular, have become the center stage of current cancer drug development. Given the growing significance of dual HDAC inhibitors, in this review, we intend to compile the development of quinazoline based HDAC dual inhibitors as anti-cancer agents.

Discovery of Novel Dihydropyrimidine and hydroxamic acid hybrids as potent Helicobacter pylori Urease inhibitors

Two novel series of Dihydropyrimidine-hydroxamic acid hybrids (4a-4l and 5a-5l) were designed, synthesized and evaluated for in vitro Helicobacter pylori urease inhibition. In vitro enzyme inhibition screening led to the discovery of three potent urease inhibitors 2-[[4-(4-hydroxy phenyl)-6-oxo-1,6-dihydropyrimidine-2-yl]-amino]-N-hydroxy acetamide (4g), 2-[[4-(4-chloro phenyl)-6-oxo-1,6-dihydropyrimidine-2-yl]-amino]-N-hydroxy acetamide (4b) and 3-[[4-(3-methoxy phenyl)-6-oxo-1,6-dihydropyrimidine-2-yl]-amino]-N-hydroxy propanamide (5l). Compound 4g showed excellent urease inhibition with IC₅₀ value of 14 ± 1 nM, indicated by its strong interactions with both metallic Ni⁺⁺ ions, Gly279, His221, Ala365, Asp362, Asn168, Arg338 and His322 residues of the active site of urease. Further, compounds 4b and 5l displayed very good activity with IC₅₀ value of 0.082 ± 0.004 µM and 0.14 ± 0.013 µM respectively compared to standard Acetohydroxamic acid (IC₅₀ - 27.4 ± 1.2 µM). Kinetic studies revealed that a mixed inhibition with both competitive and non-competitive aspects is involved in the urease inhibition mechanism. The in vitro urease inhibition results were supported by molecular docking studies. Collectively, this study indicates that 4g could be considered as promising lead molecule that can be further developed as a potent drug molecule for the treatment of Helicobacter pylori caused gastritis for further studies.

1,2,3,4-Tetrahydroisoquinoline (THIQ) as privileged scaffold for anticancer de novo drug design

Introduction: Cancer is a dreadful disorder that is emerging as one of the leading causes of mortality across the globe. The complex tumor environment, supplemented with drawbacks of the existing drugs, has made it a global health concern. The Tetrahydroisoquinoline (THIQ) ring holds an important position in medicinal chemistry due to its wide range of pharmacological properties. Several THIQ based natural products have been previously explored for their antitumor properties, making it a vital scaffold for anticancer drug design.Areas covered: This review article addresses the potential of THIQ as anticancer agents. Various medicinal chemistry strategies employed for the design and development of THIQ analogs as inhibitors or modulators of relevant anticancer targets have been discussed in detail. Moreover, the common strategies employed for the synthesis of the core scaffold are also highlighted.Expert opinion: Evidently, THIQs have tremendous potential in anticancer drug design. Some of these analogs exhibited potent activity against various cancer molecular targets. However, there are some drawbacks, such as selectivity that need addressing. The synthetic ease for constructing the core scaffold complimented with its reactivity makes it ideal for further structure-activity relationship studies. For these reasons, THIQ is a privileged scaffold for the design and development of novel anticancer agents.

Practical direct synthesis of N-aryl-substituted azacycles from N-alkyl protected arylamines using TiCl4 and DBU

A novel transformation of N-alkyl protected arylamines and cyclic ethers into N-aryl substituted azacycles is described. Alkyl groups have been used for the protection of amines in organic syntheses. In this synthesis, N-alkyl protected arylamines were reacted with cyclic ethers in the presence of TiCl4 and DBU, crucial reagents affording five- and six-membered azacycles. In particular, utilization of the novel TiCl4/DBU-mediated reaction allows various N-alkyl protected arylamines such as N-methyl-, N-ethyl-, N-isopropyl, and N-tert-butyl arylamines to be readily converted into N-aryl substituted azacycles in high yields. This practical approach using various N-alkyl arylamines leads to the efficient preparation of azacycles.

New approaches towards the synthesis of 1,2,3,4-tetrahydro isoquinoline-3-phosphonic acid (TicP)

Two new strategies for the efficient synthesis of racemic 1,2,3,4-tetrahydroisoquinoline-3-phosphonic acid (Tic^P) (±)-2 have been developed. The first strategy involves the electron-transfer reduction of the easily obtained α,β-dehydro phosphonophenylalanine followed by a Pictet-Spengler cyclization. The second strategy involves a radical decarboxylation-phosphorylation reaction on 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic). In both strategies, the highly electrophilic N-acyliminium ion is formed as a key intermediate, and the target compound is obtained in good yield using mild reaction conditions and readily available starting materials, complementing existing methodologies and contributing to the easy accessibility of (±)-2 for further research.

Structural exploration of tetrahydroisoquinoline derivatives as HDAC8 inhibitors through multi-QSAR modeling study

Histone deacetylase 8 (HDAC8) is one of the crucial HDACs responsible for influencing the epigenetic functions of the body. Overexpression of HDAC8 is found to be involved in numerous disease conditions such as tumorigenesis, cell proliferation, cancer, viral infections, neuronal disorders and other epigenetic diseases. Therefore, inhibition of HDAC8 is a primary method to combat these diseases. In this article, a multi-QSAR modeling study on tetrahydroisoquinoline derivatives was conducted to identify important contributions of the structural features of these compounds toward HDAC8 inhibition. All these QSAR modeling techniques were individually validated and justified the observations of each other. The results implied that the tetrahydroisoquinoline moiety may be effective as a cap group than as a linker moiety for HDAC8 inhibition. Different substitutions at the tetrahydroisoquinoline scaffold were also found to be crucial in modulating HDAC8 inhibition.Communicated by Ramaswamy H. Sarma.

An insight into selective and potent inhibition of histone deacetylase 8 through induced-fit docking, pharmacophore modeling and QSAR studies

Histone deacetylase 8 (HDAC8) has emerged as an important therapeutic target due to its involvement in various cancerous and neurodegenerative disease states. Since pan HDAC inhibition has been linked to various side effects, the need of the hour is to develop inhibitors truly selective for one isoform. This work attempts to explore the structural basis of selective HDAC8 inhibition by docking, pharmacophore and 3 D QSAR studies of 53 highly potent and highly selective triazol-based hydroxamic acid inhibitors. The binding modes of these novel inhibitors have been explored via Glide XP (Extra Precision) and induced-fit docking (IFD) strategies. The IFD poses of highly active and selective inhibitors showed conformational changes in active site residues like Trp141, Phe152 and Phe208, which were further verified by molecular dynamics simulations. A new CH-π interaction, which is atypical of HDAC inhibitors, was also observed in case of some highly selective inhibitors. Two pharmacophore models have been proposed; one highlights the structural basis of potency of these inhibitors and the other focuses on the selectivity. The corresponding QSAR models, obtained from alignment of the inhibitors as per the proposed pharmacophore models, are highly statistically significant. These models highlight the importance of size of the hydrophobic and aromatic groups present in the inhibitors and their contribution to activity of the inhibitors. The ADMET properties of the ligand library have also been analyzed and the predicted descriptors have been correlated with activity using principal components analysis to gain insight into the effect of pharmacokinetic properties on the activity.Communicated by Ramaswamy H. Sarma.

Next-generation of selective histone deacetylase inhibitors

Histone deacetylases (HDACs) are clinically validated epigenetic drug targets for cancer treatment. HDACs inhibitors (HDACis) have been successfully applied against a series of cancers. First-generation inhibitors are mainly pan-HDACis that target multiple isoforms which might lead to serious side effects. At present, the next-generation HDACis are mainly focused on being class- or isoform-selective which can provide improved risk–benefit profiles compared to non-selective inhibitors. Because of the rapid development in next-generation HDACis, it is necessary to have an updated and state-of-the-art overview. Here, we summarize the strategies and achievements of the selective HDACis.

Histone deacetylases (HDACs) are clinically validated epigenetic drug targets for cancer treatment.

Histone deacetylase 8 (HDAC8) and its inhibitors with selectivity to other isoforms: An overview

The histone deacetylases (HDACs) enzymes provided crucial role in transcriptional regulation of cells through deacetylation of nuclear histone proteins. Discoveries related to the HDAC8 enzyme activity signified the importance of HDAC8 isoform in cell proliferation, tumorigenesis, cancer, neuronal disorders, parasitic/viral infections and other epigenetic regulations. The pan-HDAC inhibitors can confront these conditions but have chances to affect epigenetic functions of other HDAC isoforms. Designing of selective HDAC8 inhibitors is a key feature to combat the pathophysiological and diseased conditions involving the HDAC8 activity. This review is concerned about the structural and positional aspects of HDAC8 in the HDAC family. It also covers the contributions of HDAC8 in the pathophysiological conditions, a preliminary discussion about the recent scenario of HDAC8 inhibitors. This review might help to deliver the structural, functional and computational information in order to identify and design potent and selective HDAC8 inhibitors for target specific treatment of diseases involving HDAC8 enzymatic activity.

A general and atom-efficient continuous-flow approach to prepare amines, amides and imines via reactive N-chloramines

Chloramines are an important class of reagents, providing a convenient source of chlorine or electrophilic nitrogen. However, the instability of these compounds is a problem which makes their isolation and handling difficult. To overcome these hazards, a continuous-flow approach is reported which generates and immediately reacts N-chloramines directly, avoiding purification and isolation steps. 2-Chloramines were produced from the reaction of styrenes with N-alkyl-N-sulfonyl-N-chloramines, whilst N-alkyl or N,N'-dialkyl-N-chloramines reacted with anisaldehyde in the presence of t-BuO2H oxidant to afford amides. Primary and secondary imines were produced under continuous conditions from the reaction of N-chloramines with base, with one example subsequently reduced under asymmetric conditions to produce a chiral amine in 94% ee.

Structure–activity relationships of hydroxamate-based histone deacetylase-8 inhibitors: reality behind anticancer drug discovery

The pan-histone deacetylase (HDAC) inhibitors comprise a fish-like structural orientation where hydrophobic aryl- and zinc-binding groups act as head and tail, respectively of a fish. The linker moiety correlates the body of the fish linking head and tail groups. Despite these pan-HDAC inhibitors, selective HDAC-8 inhibitors are still in demand as a safe remedy. HDAC-8 is involved in invasion and metastasis in cancer. This review deals with the rationale behind HDAC-8 inhibitory activity and selectivity along with detailed structure–activity relationships of diverse hydroxamate-based HDAC-8 inhibitors. HDAC-8 inhibitory potency may be increased by modifying the fish-like pharmacophoric features of such type of pan-HDAC inhibitors. This review may provide a preliminary basis to design and optimize new lead molecules with higher HDAC-8 inhibitory activity. This work may surely enlighten in providing useful information in the field of target-specific anticancer therapy.

Discovery of a tetrahydroisoquinoline-based HDAC inhibitor with improved plasma stability

Histone deacetylase inhibitors with desirable pharmacokinetic profiles which can be delivered to solid tumor tissues in large amount might be promising to treat solid tumor effectively. Herein, structural modification of a previously reported tetrahydroisoquinoline-based HDAC inhibitor 1 was carried out to improve its plasma stability for more feasible drug delivery. Among three newly synthesized analogs, the in vitro rat plasma stability of compound 2 (t_1/2=630min) was over 5-fold improved than its parent 1 (t_1/2=103min). In vitro activity evaluation showed that compound 2 and 1 exhibited similar HDACs inhibitory activity, which was validated by western blot analysis and antiproliferative assay. Moreover, compared with 1, compound 2 exhibited comparable, if not higher, in vivo antitumor activity in a human breast carcinoma (MDA-MB-231) xenograft model.

Design and Synthesis of C3-Substituted β-Carboline-Based Histone Deacetylase Inhibitors with Potent Antitumor Activities

A series of hydroxamic acid histone deacetylase (HDAC) inhibitors in which the β-carboline motif has been incorporated were designed and synthesized. The effect of substitution at the C3 amide on HDAC inhibition and antiproliferative activities was investigated. Most of these compounds were found to display significant HDAC inhibitory effects and good antiproliferative activity, with IC₅₀ values in the low-micromolar range. In particular, the HDAC inhibition IC₅₀ value of N-(2-(dimethylamino)ethyl)-N-(4-(hydroxylcarbamoyl)benzyl)-1-(4-methoxyphenyl)-9H-pyrido[3,4-b]indole-3-carboxamide (9 h) is five-fold lower than that of suberoylanilide hydroxamic acid (SAHA, vorinostat). Furthermore, 9 h was found to increase the acetylation of histone H3 and α-tubulin, and to induce DNA damage as evidenced by hypochromism and enhanced phosphorylation of histone H2AX. Compound 9 h inhibits Stat3, Akt, and ERK signaling, important cell-growth-promoting pathways that are aberrantly activated in most cancers. Finally, 9 h showed reasonable solubility and permeability in Caco-2 cells. Our findings suggest that these novel β-carboline-based HDAC inhibitors may hold great promise as therapeutic agents for the treatment of human cancers.

Development of novel β-carboline-based hydroxamate derivatives as HDAC inhibitors with DNA damage and apoptosis inducing abilities

A series of novel β-carboline-based hydroxamate derivatives (8a-n) as HDAC inhibitors have been designed and synthesized. Most of these compounds displayed potent histone deacetylase inhibitory effects and good antiproliferative activity with IC₅₀s in the low micromolar range. One of the most potent compounds (8k) showed the strongest inhibition of the proliferation of human hepatocellular carcinoma (HCC) cells in vitro, with IC₅₀ values lower than that of the currently approved HDAC inhibitor SAHA. Compound 8k also increased acetylation of histone H3 and α-tubulin, consistent with its potent HDAC inhibition. Importantly, 8k induced hypochromism by electrostatic interactions with CT-DNA, suggesting potential induction of DNA damage. Finally, 8k significantly induced HepG2 cell apoptosis by regulating apoptotic relative proteins expression. Together, our findings suggest that these novel β-carboline-based hydroxamate derivatives may provide a new framework for the discovery of novel antitumor agents for the intervention of human carcinoma cells.

Design, synthesis and biological evaluation of novel coumarin-based benzamides as potent histone deacetylase inhibitors and anticancer agents

Histone deacetylases (HDACs) are attractive therapeutic targets for the treatment of cancer and other diseases. It has four classes (I-IV), among them especially class I isozyme are involved in promoting tumor cells proliferation, angiogenesis, differentiation, invasion and metastasis and also viable targets for cancer therapeutics. A novel series of coumarin-based benzamides was designed and synthesized as HDAC inhibitors. The cytotoxic activity of the synthesized compounds (8a-u) was evaluated against six human cancer cell lines including HCT116, A2780, MCF7, PC3, HL60 and A549 and a single normal cell line (Huvec). We evaluated their inhibitory activities against pan HDAC and HDAC1 isoform. Four compounds (8f, 8q, 8r and 8u) showed significant cytotoxicity with IC₅₀ in the range of 0.53-57.59 μM on cancer cells and potent pan-HDAC inhibitory activity (consists of HDAC isoenzymes) (IC₅₀ = 0.80-14.81 μM) and HDAC1 inhibitory activity (IC₅₀ = 0.47-0.87 μM and also, had no effect on Huvec (human normal cell line) viability (IC₅₀ > 100 μM). Among them, 8u displayed a higher potency for HDAC1 inhibition with IC₅₀ value of 0.47 ± 0.02 μM near equal to the reference drug Entinostat (IC₅₀ = 0.41 ± 0.06 μM). Molecular docking studies and Molecular dynamics simulation of compound 8a displayed possible mode of interaction between this compound and HDAC1enzyme.

Selective histone deacetylase small molecule inhibitors: recent progress and perspectives

INTRODUCTION

Since the first pan-HDAC inhibitor SAHA was approved by U.S. FDA 10 years ago, HDACs including SIRT1-7 have received significant attention due to the fact that aberrant histone deacetylase activtiy has been implicated in a variety of human diseases, such as cancers, virus infection, and neurodegenerative diseases. During the past years, a considerable achievement of development of isoform- or class-selective HDAC inhibitors has been made, yielding many drug candidates for further clinical studies, which represents a state-of-the-art technology in the drug discovery arena. Areas covered: This review covers new patents and articles about isoform- or class-selective HDAC inhibitors during the last four years, as well as the therapeutic potential of these compounds. Expert opinion: HDACs represent one of the most promising therapeutic targets, particularly for tumor therapy though their roles in cancer are still blurry. From 2012 to present, along with the advances of structural biology and homology models, lots of isoform- or class-selective HDAC inhibitors, such as hydroxamic acids and benzamides with various capping groups were found, providing a promising way to circumvent drug toxicity and side-effect issues, as well as providing chemical probes for further better understanding of the biological process related to specific isoform.

Discovery of BC-01, a novel mutual prodrug (hybrid drug) of ubenimex and fluorouracil as anticancer agent

We designed and synthesized a novel mutual prodrug, named BC-01 (3), by integrating ubenimex and Fluorouracil (5-FU) into one molecule based on prior research results that showed that a combination of the aminopeptidase N (CD13) inhibitor, ubenimex, and the cytotoxic antitumor agent, 5-FU, exhibited improved in vitro and in vivo antitumor efficiency. 3 showed potent inhibitory activity against CD13 enzymatic activity. Compared with ubenimex, 3 exhibited more potent anti-angiogenesis effects, and compared with the approved 5-FU prodrug, capecitabine, 3 exhibited more potent tumor growth inhibitory and anti-metastasis effects. Additionally, compared with 5-FU or 5-FU plus ubenimex, 3 also exhibited a superior antitumor efficiency even in our 5-FU-resistant mice model. Other antitumor agents could be conjugated with ubenimex using this strategy to obtain novel mutual prodrugs with promising antitumor potency.

Novel β-Carboline/Hydroxamic Acid Hybrids Targeting Both Histone Deacetylase and DNA Display High Anticancer Activity via Regulation of the p53 Signaling Pathway

A novel series of hybrids from β-carboline and hydroxamic acid were designed and synthesized. Several compounds (5m, 11b-d, and 11h) not only exerted significant antiproliferation activity against four human colorectal cancer (CRC) cell lines but also showed histone deacetylase inhibitory effects in vitro. The most potent compound, 11c, exhibited anticancer potency sevenfold higher than that of SAHA. 11c triggered more significant cancer cell apoptosis than did SAHA by cleavage of both PARP and caspase 3 in a dose-dependent manner. Furthermore, 11c simultaneously increased the acetylation of histone H3 and α-tubulin, enhanced expression of DNA damage markers histone H2AX phosphorylation and p-p53 (Ser15), and activated p53 signaling pathway in HCT116 cells. Finally, 11c showed low acute toxicity in mice and inhibited the growth of implanted human CRC in mice more potently than did SAHA. Together, 11c possessed potent antitumor activity and may be a promising candidate for the potential treatment of human CRC.

Syntheses and discovery of a novel class of cinnamic hydroxamates as histone deacetylase inhibitors by multimodality molecular imaging in living subjects

Histone deacetylases (HDAC) that regulate gene expression are being explored as cancer therapeutic targets. In this study, we focused on HDAC6 based on its ability to inhibit cancerous Hsp90 chaperone activities by disrupting Hsp90/p23 interactions. To identify novel HDAC6 inhibitors, we used a dual-luciferase reporter system in cell culture and living mice by bioluminescence imaging (BLI). On the basis of existing knowledge, a library of hydrazone compounds was generated for screening by coupling cinnamic hydroxamates with aldehydes and ketones. Potency and selectivity were determined by in vitro HDAC profiling assays, with further evaluation to inhibit Hsp90(α/β)/p23 interactions by BLI. In this manner, we identified compound 1A12 as a dose-dependent inhibitor of Hsp90(α/β)/p23 interactions, UKE-1 myeloid cell proliferation, p21(waf1) upregulation, and acetylated histone H3 levels. 1A12 was efficacious in tumor xenografts expressing Hsp90(α)/p23 reporters relative to carrier control-treated mice as determined by BLI. Small animal (18)F-FDG PET/CT imaging on the same cohort showed that 1A12 also inhibited glucose metabolism relative to control subjects. Ex vivo analyses of tumor lysates showed that 1A12 administration upregulated acetylated-H3 by approximately 3.5-fold. Taken together, our results describe the discovery and initial preclinical validation of a novel selective HDAC inhibitor.

Current trends in the development of histone deacetylase inhibitors: a review of recent patent applications

Histone deacetylases (HDACs) have become an important target for the treatment of cancer and other diseases. Currently, more than ten HDAC inhibitors have entered clinical studies and two of them have already reached the market. The hydroxamic acid derivative SAHA (also known as vorinostat or Zolinza®) and the cyclic depsipeptide FK228 (romidepsin or Istodax®) have gained approval from the US FDA for the treatment of cutaneous T-cell lymphoma. Nevertheless, there has been a continuous effort aimed at discovering a new generation of clinical candidates with improved pharmaceutical properties. This review provides a summary of the most recent patents published from mid-2009 to mid-2011.