Romidepsin for cutaneous T-cell lymphoma

Direct Amidation to Access 3-Amido-1,8-Naphthalimides Including Fluorescent Scriptaid Analogues as HDAC Inhibitors

Methodology to access fluorescent 3-amido-1,8-naphthalimides using direct Buchwald-Hartwig amidation is described. The protocol was successfully used to couple a number of substrates (including an alkylamide, an arylamide, a lactam and a carbamate) to 3-bromo-1,8-naphthalimide in good yield. To further exemplify the approach, a set of scriptaid analogues with amide substituents at the 3-position were prepared. The new compounds were more potent than scriptaid at a number of histone deacetylase (HDAC) isoforms including HDAC6. Activity was further confirmed in a whole cell tubulin deacetylation assay where the inhibitors were more active than the established HDAC6 selective inhibitor Tubastatin. The optical properties of these new, highly active, compounds make them amenable to cellular imaging studies and theranostic applications.

Romidepsin (FK228), A Histone Deacetylase Inhibitor and its Analogues in Cancer Chemotherapy

BACKGROUND

Human HDACs represent a group of enzymes able to modify histone and non-histone proteins, which interact with DNA to generate chromatin. The correlation between irregular covalent modification of histones and tumor development has been proved over the last decades. Therefore, HDAC inhibitors are considered as potential drugs in cancer treatment. Romidepsin (FK228), Belinostat (PXD-101), Vorinostat (SAHA), Panobinostat (LBH-589) and Chidamide were approved by FDA as novel antitumor agents.

OBJECTIVE

The aim of this review article is to highlight the structure-activity relationships of several FK228 analogues as HDAC inhibitors. In addition, the synergistic effects of a dual HDAC/PI3K inhibition by some derivatives have been investigated.

MATERIALS AND METHODS

PubMed, MEDLINE, CAPLUS, SciFinder Scholar database were considered by selecting articles which fulfilled the objectives of this review, dating from 2015 till present time.

RESULTS

HDAC inhibitors have a significant role in cancer pathogenesis and evolution. Class I HDAC isoforms are expressed in many tumor types, therefore, potent and selective Class I HDAC inhibitors are of great interest as candidate therapeutic agents with limited side effects. By structurebased optimization, several FK228 analogues [15 (FK-A5), 22, 23 and 26 (FK-A11)] were identified, provided with significant activity against Class I HDAC enzymes and dose dependent antitumor activity. Compound 26 was recognized as an interesting HDAC/PI3K dual inhibitor (IC₅₀ against p110α of 6.7 μM while for HDAC1 inhibitory activity IC₅₀ was 0.64 nM).

CONCLUSION

Romidepsin analogues HDAC inhibitors have been confirmed as useful anticancer agents. In addition, dual HDAC/PI3K inhibition showed by some of them exhibited synergistic effects in inducing apoptosis in human cancer cells. Further studies on FK228 analogues may positively contribute to the availability of potent agents in tumor treatment.

Investigation of the in vitro and in vivo efficacy of peptoid-based HDAC inhibitors with dual-stage antiplasmodial activity

Histone deacetylases (HDACs) have been identified as emerging antiplasmodial drug targets. In this work, we report on the synthesis, structure-activity relationships, metabolic stability and in vivo efficacy of new peptoid-based HDAC inhibitors with dual-stage antiplasmodial activity. A mini library of HDAC inhibitors was synthesized using a one-pot, multi-component protocol or submonomer pathways. The screening of the target compounds for their activity against asexual blood stage parasites, human cell cytotoxicity, liver stage parasites, and selected human HDAC isoforms provided important structure-activity relationship data. The most promising HDAC inhibitor from this series, compound 3n, demonstrated potent activity against drug-sensitive and drug-resistant asexual stage P. falciparum parasites and was selective for the parasite versus human cells (Pf3D7 IC₅₀ 0.016 μM; SI^HepG2/Pf3D7 573; PfDd2 IC₅₀ 0.002 μM; SI^HepG2/PfDd2 4580) combined with activity against P. berghei exoerythrocytic liver stages (PbEEF IC₅₀ 0.48 μM). While compound 3n displayed high stability in human (Cl_int 5 μL/min/mg) and mouse (Cl_int 6 μL/min/mg) liver microsomes, only modest oral in vivo efficacy was observed in P. berghei infected mice. Together these data provide a foundation for future work to improve the properties of these dual-stage inhibitors as drug leads for malaria.

An ELISA method to assess HDAC inhibitor-induced alterations to P. falciparum histone lysine acetylation

The prevention and treatment of malaria requires a multi-pronged approach, including the development of drugs that have novel modes of action. Histone deacetylases (HDACs), enzymes involved in post-translational protein modification, are potential new drug targets for malaria. However, the lack of recombinant P. falciparum HDACs and suitable activity assays, has made the investigation of compounds designed to target these enzymes challenging. Current approaches are indirect and include assessing total deacetylase activity and protein hyperacetylation via Western blot. These approaches either do not allow differential compound effects to be determined or suffer from low throughput. Here we investigated dot blot and ELISA methods as new, higher throughput assays to detect histone lysine acetylation changes in P. falciparum parasites. As the ELISA method was found to be superior to the dot blot assay using the control HDAC inhibitor vorinostat, it was used to evaluate the histone H3 and H4 lysine acetylation changes mediated by a panel of six HDAC inhibitors that were shown to inhibit P. falciparum deacetylase activity. Vorinostat, panobinostat, trichostatin A, romidepsin and entinostat all caused an ~3-fold increase in histone H4 acetylation using a tetra-acetyl lysine antibody. Tubastatin A, the only human HDAC6-specific inhibitor tested, also caused H4 hyperacetylation, but to a lesser extent than the other compounds. Further investigation revealed that all compounds, except tubastatin A, caused hyperacetylation of the individual N-terminal H4 lysines 5, 8, 12 and 16. These data indicate that tubastatin A impacts P. falciparum H4 acetylation differently to the other HDAC inhibitors tested. In contrast, all compounds caused hyperacetylation of histone H3. In summary, the ELISA developed in this study provides a higher throughput approach to assessing differential effects of antiplasmodial compounds on histone acetylation levels and is therefore a useful new tool in the investigation of HDAC inhibitors for malaria.

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P. falciparum histone lysine acetylation was compared using dot blot and ELISA.

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ELISA was more reproducible than dot blot in acetylation assays.

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ELISA was used to assess acetylation changes induced by anti-cancer HDAC inhibitors.

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Tubastatin A showed a different histone H4 acetylation profile to other compounds.

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This new method will facilitate the study of HDAC inhibitors for malaria.

Natural Products Impacting DNA Methyltransferases and Histone Deacetylases

Epigenetics refers to heritable changes in gene expression and chromatin structure without change in a DNA sequence. Several epigenetic modifications and respective regulators have been reported. These include DNA methylation, chromatin remodeling, histone post-translational modifications, and non-coding RNAs. Emerging evidence has revealed that epigenetic dysregulations are involved in a wide range of diseases including cancers. Therefore, the reversible nature of epigenetic modifications concerning activation or inhibition of enzymes involved could be promising targets and useful tools for the elucidation of cellular and biological phenomena. In this review, emphasis is laid on natural products that inhibit DNA methyltransferases (DNMTs) and histone deacetylases (HDACs) making them promising candidates for the development of lead structures for anticancer-drugs targeting epigenetic modifications. However, most of the natural products targeting HDAC and/or DNMT lack isoform selectivity, which is important for determining their potential use as therapeutic agents. Nevertheless, the structures presented in this review offer the well-founded basis that screening and chemical modifications of natural products will in future provide not only leads to the identification of more specific inhibitors with fewer side effects, but also important features for the elucidation of HDAC and DNMT function with respect to cancer treatment.

Design, synthesis and evaluation of belinostat analogs as histone deacetylase inhibitors

Aim: Histone deacetylase (HDAC) is an attractive target for antitumor therapy. Therefore, the development of novel HDAC inhibitors is warranted. Materials & methods: A series of HDAC inhibitors based on N-hydroxycinnamamide fragment was designed as the clinically used belinostat analog using amide as the connecting unit. All target compounds were evaluated for their in vitro HDAC inhibitory activities and some selected compounds were tested for their antiproliferative activities. Conclusion: Among them, compound 7e showed an IC₅₀ value of 11.5 nM in inhibiting the HDAC in a pan-HDAC assay, being the most active compound of the series.

Histone Deacetylase Inhibitors in Tumor Immunotherapy

BACKGROUND

With an increasing understanding of the antitumor immune response, considerable progress has been made in the field of tumor immunotherapy in the last decade. Inhibition of histone deacetylases represents a new strategy in tumor therapy and histone deacetylase inhibitors have been recently developed and validated as potential antitumor drugs. In addition to the direct antitumor effects, histone deacetylase inhibitors have been found to have the ability to improve tumor recognition by immune cells that may contribute to their antitumor activity. These immunomodolutory effects are desirable, and their in-depth comprehension will facilitate the design of novel regimens with improved clinical efficacy.

OBJECTIVE

Our goal here is to review recent developments in the application of histone deacetylase inhibitors as immune modulators in cancer treatment.

METHODS

Systemic compilation of the relevant literature in this field.

RESULTS & CONCLUSION

In this review, we summarize recent advances in the understanding of how histone deacetylase inhibitors alter immune process and discuss their effects on various cytokines. We also discuss the challenges to optimize the use of these inhibitors as immune modulators in cancer treatment. Information gained from this review will be valuable to this field and may be helpful for designing tumor immunotherapy trials involving histone deacetylase inhibitors.

The histone deacetylase inhibitor Romidepsin induces as a cascade of differential gene expression and altered histone H3K9 marks in myeloid leukaemia cells

Myelodysplastic syndromes (MDS) are a heterogeneous, clonal haematopoietic disorder, with ~1/3 of patients progressing to acute myeloid leukaemia (AML). Many elderly MDS patients do not tolerate intensive therapeutic regimens, and therefore have an unmet need for better tolerated therapies.

Epigenetics is important in the pathogenesis of MDS/AML with DNA methylation, and histone acetylation the most widely studied modifications. Epigenetic therapeutic agents have targeted the reversible nature of these modifications with some clinical success. The aim of this study was to characterise the molecular consequences of treatment of MDS and AML cells with the histone deacetylase inhibitor (HDACi) Romidepsin.

Romidepsin as a single agent induced cell death with an increasing dose and time profile associated with increased acetylation of histone H3 lysine 9 (H3K9) and decreased HDAC activity. Gene expression profiling, qPCR, network and pathway analysis recognised that oxidation-reduction was involved in response to Romidepsin. ROS was implicated as being involved post-treatment with the involvement of TSPO and MPO.

Genomic analysis uncoupled the differences in protein-DNA interactions and gene regulation. The spatial and temporal transcriptional differences associated with acetylated, mono- and tri-methylated H3K9, representative of two activation and a repression mark respectively, were identified. Bioinformatic analysis uncovered positional enrichment and transcriptional differences between these marks; a degree of overlap with increased/decreased gene expression that correlates to increased/decreased histone modification. Overall, this study has unveiled a number of underlying mechanisms of the HDACi Romidepsin that could identify potential drug combinations for use in the clinic.

Elucidating the mechanism of action of domatinostat (4SC-202) in cutaneous T cell lymphoma cells

Background

Targeting epigenetic modifiers is effective in cutaneous T cell lymphoma (CTCL). However, there is a need for further improvement of this therapeutic approach. Here, we compared the mode of action of romidepsin (FK228), an established class I histone deacetylase inhibitor, and domatinostat (4SC-202), a novel inhibitor of class I HDACs, which has been reported to also target the lysine-specific histone demethylase 1A (LSD1).

Methods

We performed MTS assays and flow cytometric analyses of propidium iodide or annexin V-stained cells to assess drug impact on cellular proliferation, cell cycle distribution, and survival. Histone acetylation and methylation as well as caspase activation was analyzed by immunoblot. Gene expression analysis was performed using NanosString technology. Knockdown and knockout of LSD1 was achieved with shRNA and CRISPR/Cas9, respectively, while the CRISPR/Cas9 synergistic activation mediator system was used to induce expression of endogenous HDACs and LSD1. Furthermore, time-lapse fluorescence microscopy and an in vitro tubulin polymerization assay were applied.

Results

While FK228 as well as 4SC-202 potently induced cell death in six different CTCL cell lines, only in the case of 4SC-202 death was preceded by an accumulation of cells in the G2/M phase of the cell cycle. Surprisingly, apoptosis and accumulation of cells with double DNA content occurred already at 4SC-202 concentrations hardly affecting histone acetylation and methylation, and provoking significantly less changes in gene expression compared to biologically equivalent doses of FK228. Indeed, we provide evidence that the 4SC-202-induced G2/M arrest in CTCL cells is independent of de novo transcription. Furthermore, neither enforced expression of HDAC1 nor knockdown or knockout of LSD1 affected the 4SC-202-induced effects. Since time-lapse microscopy revealed that 4SC-202 could affect mitotic spindle formation, we performed an in vitro tubulin polymerization assay revealing that 4SC-202 can directly inhibit microtubule formation.

Conclusions

We demonstrate that 4SC-202, a drug currently tested in clinical trials, effectively inhibits growth of CTCL cells. The anti-cancer cell activity of 4SC-202 is however not limited to LSD1-inhibition, modulation of histone modifications, and consecutive alteration of gene expression. Indeed, the compound is also a potent microtubule-destabilizing agent.

Electronic supplementary material

The online version of this article (10.1186/s13045-019-0719-4) contains supplementary material, which is available to authorized users.

Crosstalk among the proteome, lysine phosphorylation, and acetylation in romidepsin-treated colon cancer cells

Romidepsin (FK228) is one of the most promising histone-deacetylase inhibitors due to its potent antitumor activity, and has been used as a practical option for cancer therapy. However, FK228-induced changes in protein modifications and the crosstalk between different modifications has not been reported. To better understand the underlying mechanisms of FK228-related cancer therapy, we investigated the acetylome, phosphorylation, and crosstalk between modification datasets in colon cancer cells treated with FK228 by using stable-isotope labeling with amino acids in cell culture and affinity enrichment, followed by high-resolution liquid chromatography tandem mass spectrometry analysis. In total, 2728 protein groups, 1175 lysine-acetylation sites, and 4119 lysine-phosphorylation sites were quantified. When the quantification ratio thresholds were set to > 2.0 and < 0.5, respectively, a total of 115 and 38 lysine-acetylation sites in 85 and 32 proteins were quantified as increased and decreased targets, respectively, and 889 and 370 lysine-phosphorylation sites in 599 and 289 proteins were quantified as increased and decreased targets, respectively. Furthermore, we identified 274 proteins exhibiting both acetylation and phosphorylation modifications. These findings indicated possible involvement of these proteins in FK228-related treatment of colon cancer, and provided insight for further analysis of their biological function.

Design and synthesis of benzodiazepine analogs as isoform-selective human lysine deacetylase inhibitors

A comprehensive investigation was performed to identify new benzodiazepine (BZD) derivatives as potent and selective human lysine deacetylase inhibitors (hKDACis). A total of 108 BZD compounds were designed, synthesized and from that 104 compounds were biologically evaluated against human lysine deacetylases (hKDACs) 1, 3 and 8 (class I) and 6 (class IIb). The most active compounds showed mid-nanomolar potencies against hKDACs 1, 3 and 6 and micromolar activity against hKDAC8, while a promising compound (6q) showed selectivity towards hKDAC3 among the different enzyme isoforms. An hKDAC6 homology model, refined by molecular dynamics simulation was generated, and molecular docking studies performed to rationalize the dominant ligand-residue interactions as well as to define structure-activity-relationships. Experimental results confirmed the usefulness of the benzodiazepine moiety as capping group when pursuing hKDAC isoform-selectivity inhibition, suggesting its continued use when designing new hKDACis.

Development and validation of a sensitive HPLC-MS/MS method for determination of chidamide (epidaza), a new benzamide class of selective histone deacetylase inhibitor, in human plasma and its clinical application

Chidamide (epidaza), a new oral isotype-selective histone deacetylase inhibitor (HDACi), which is just approved in China for the treatment of recurrent or refractory peripheral T-cell lymphoma (PTCL) in December 2014, is the first listed benzamide class of HDACi in the world, and is currently undergoing global clinical trials for solid tumor treatments. Here, we report a sensitive, rapid and robust HPLC-MS/MS method for determination of chidamide in human plasma. Plasma sample was subjected to a simple acetonitrile protein precipitation containing MS-275 used as an internal standard (IS). Chromatography was performed on a Hypersil GOLD C18 analytical column, using a gradient methanol/water mobile phase containing 0.1% formic acid. A tandem mass spectrometer equipped with electrospray ionization source was used as detector and operated in the positive-ion mode. Selected reaction monitoring (SRM) using the precursor/ product transitions (m/z) of 391.1/265.1 for chidamide and 377.1/359.2 for IS were used for quantification, respectively. Good linearity was obtained in the range of 1-1000ng/mL. The method gave R.S.D.% values for precision always lower than 13.8% and R.E.% values for accuracy between -3.7 and 9.1%. In addition, the specificity, recovery, stability and matrix effect were satisfactory too. The method is now being successfully applied to plasma samples as part of an ongoing chidamide phase Ib clinical trial in patients with solid tumors, and had demonstrated consistent AUClast and t1/2 results with the published phase I pharmacokinetic data, which was also analyzed by this method, thus further confirming the reproducibility and accuracy during its clinical application. Considering the excellent performance of this method, it will continue being utilized for future clinical developments of chidamide and for routine monitoring of plasma exposure of chidamide during its clinical therapy.