Discovery of Novel Histone Deacetylase 6 (HDAC6) Inhibitors with Enhanced Antitumor Immunity of Anti-PD-L1 Immunotherapy in Melanoma.

A series of 2-phenylthiazole analogues were designed and synthesized as potential histone deacetylase 6 (HDAC6) inhibitors based on compound 12c (an HDAC6/tubulin dual inhibitor discovered by us recently) and CAY10603 (a known HDAC6 inhibitor). Among them, compound XP5 was the most potent HDAC6 inhibitor with an IC50 of 31 nM and excellent HDAC6 selectivity (SI = 338 for HDAC6 over HDAC3). XP5 also displayed high antiproliferative activity against various cancer cell lines including the HDACi-resistant YCC3/7 gastric cancer cells (IC50 = 0.16-2.31 µM), better than CAY10603. Further, XP5 (50 mg/kg) exhibited significant antitumor efficacy in a melanoma tumor model with a tumor growth inhibition (TGI) of 63% without apparent toxicity. Moreover, XP5 efficiently enhanced the in vivo antitumor immune response when combined with a small-molecule PD-L1 inhibitor, as demonstrated by the increased tumor-infiltrating lymphocytes and reduced PD-L1 expression levels. Taken together, the above results suggest that XP5 is a promising HDAC6 inhibitor deserving further investigation.

Intravitreal HDAC Inhibitor Belinostat Effectively Eradicates Vitreous Seeds Without Retinal Toxicity In Vivo in a Rabbit Retinoblastoma Model.

Purpose: Current melphalan-based regimens for intravitreal chemotherapy for retinoblastoma vitreous seeds are effective but toxic to the retina. Thus, alternative agents are needed. Based on the known biology of histone deacetylases (HDACs) in the retinoblastoma pathway, we systematically studied whether the HDAC inhibitor belinostat is a viable, molecularly targeted alternative agent for intravitreal delivery that might provide comparable efficacy, without toxicity. Methods: In vivo pharmacokinetic experiments in rabbits and in vitro cytotoxicity experiments were performed to determine the 90% inhibitory concentration (IC90). Functional toxicity by electroretinography and structural toxicity by optical coherence tomography (OCT), OCT angiography, and histopathology were evaluated in rabbits following three injections of belinostat 350 µg (2× IC90) or 700 µg (4× IC90), compared with melphalan 12.5 µg (rabbit equivalent of the human dose). The relative efficacy of intravitreal belinostat versus melphalan to treat WERI-Rb1 human cell xenografts in rabbit eyes was directly quantified. RNA sequencing was used to assess belinostat-induced changes in RB cell gene expression. Results: The maximum nontoxic dose of belinostat was 350 µg, which caused no reductions in electroretinography parameters, retinal microvascular loss on OCT angiography, or retinal degeneration. Melphalan caused severe retinal structural and functional toxicity. Belinostat 350 µg (equivalent to 700 µg in the larger human eye) was equally effective at eradicating vitreous seeds in the rabbit xenograft model compared with melphalan (95.5% reduction for belinostat, P < 0.001; 89.4% reduction for melphalan, P < 0.001; belinostat vs. melphalan, P = 0.10). Even 700 µg belinostat (equivalent to 1400 µg in humans) caused only minimal toxicity. Widespread changes in gene expression resulted. Conclusions: Molecularly targeted inhibition of HDACs with intravitreal belinostat was equally effective as standard-of-care melphalan but without retinal toxicity. Belinostat may therefore be an attractive agent to pursue clinically for intravitreal treatment of retinoblastoma.

A quantitative in vivo assay for craniofacial developmental toxicity of histone deacetylases.

Many bony features of the face develop from endochondral ossification of preexisting collagen-rich cartilage structures. The proper development of these cartilage structures is essential to the morphological formation of the face. The developmental programs governing the formation of the pre-bone facial cartilages are sensitive to chemical compounds that disturb histone acetylation patterns and chromatin structure. We have taken advantage of this fact to develop a quantitative morphological assay of craniofacial developmental toxicity based on the distortion and deterioration of facial cartilage structures in zebrafish larvae upon exposure to increasing concentrations of several well-described histone deacetylase inhibitors. In this assay, we measure the angle formed by the developing ceratohyal bone as a precise, sensitive and quantitative proxy for the overall developmental status of facial cartilages. Using the well-established developmental toxicant and histone deacetylase-inhibiting compound valproic acid along with 12 structurally related compounds, we demonstrate the applicability of the ceratohyal angle assay to investigate structure-activity relationships.

Inhibition of human UDP-glucuronosyltransferase enzyme by belinostat: Implications for drug-drug interactions.

Belinostat is a pan-histone deacetylase (HDAC) inhibitor which recently approved for the treatment of relapsed/refractory Peripheral T-cell lymphomas (PTCL). To assess drug-drug interactions (DDIs) potential of belinostat via inhibition of UDP-glucuronosyltransferases (UGTs), the effects of belinostat on UGTs activities were investigated using the non-selective probe substrate 4-methylumbelliferone (4-MU) and trifluoperazine (TFP) by UPLC-MS/MS. Belinostat exhibited a wide range of inhibition against UGTs activities, particularly a potent non-competitive inhibition against UGT1A3, and weak inhibition against UGT1A1, 1A7, 1A8, 2B4 and 2B7. Further, in vitro-in vivo extrapolation (IVIVE) approaches were used to predict the risk of DDI arising from inhibition of UGTs. Our data indicate that the intravenous infusion of belinostat at clinical available dose can contribute a significant increase to the AUC of co-administrated drugs primarily cleared by UGT1A3 or UGT1A1, which will result in potential DDIs. In contrast, oral administrated belinostat is unlikely to cause significant DDIs through inhibition of glucuronidation.

In Vitro Assessment of the Genotoxic Hazard of Novel Hydroxamic Acid- and Benzamide-Type Histone Deacetylase Inhibitors (HDACi).

Histone deacetylase inhibitors (HDACi) are already approved for the therapy of leukemias. Since they are also emerging candidate compounds for the treatment of non-malignant diseases, HDACi with a wide therapeutic window and low hazard potential are desirable. Here, we investigated a panel of 12 novel hydroxamic acid- and benzamide-type HDACi employing non-malignant V79 hamster cells as toxicology guideline-conform in vitro model. HDACi causing a ≥10-fold preferential cytotoxicity in malignant neuroblastoma over non-malignant V79 cells were selected for further genotoxic hazard analysis, including vorinostat and entinostat for control. All HDACi selected, (i.e., KSK64, TOK77, DDK137 and MPK77) were clastogenic and evoked DNA strand breaks in non-malignant V79 cells as demonstrated by micronucleus and comet assays, histone H2AX foci formation analyses (γH2AX), DNA damage response (DDR) assays as well as employing DNA double-strand break (DSB) repair-defective VC8 hamster cells. Genetic instability induced by hydroxamic acid-type HDACi seems to be independent of bulky DNA adduct formation as concluded from the analysis of nucleotide excision repair (NER) deficient mutants. Summarizing, KSK64 revealed the highest genotoxic hazard and DDR stimulating potential, while TOK77 and MPK77 showed the lowest DNA damaging capacity. Therefore, these compounds are suggested as the most promising novel candidate HDACi for subsequent pre-clinical in vivo studies.

Phase I trial of belinostat in combination with 13-cis-retinoic acid in advanced solid tumor malignancies: a California Cancer Consortium NCI/CTEP sponsored trial.

PURPOSE: The reported maximum tolerated dose (MTD) of single-agent belinostat is 1000 mg/m2 given days 1-5, every 21 days. Pre-clinical evidence suggests histone deacetylase inhibitors enhance retinoic acid signaling in a variety of solid tumors. We conducted a phase I study of belinostat combined with 50-100 mg/m2/day 13-cis-retinoic acid (13-cRA) in patients with advanced solid tumors. METHODS: Belinostat was administered days 1-5 and 13-cRA days 1-14, every 21 days. Dose-limiting toxicity (DLT) was defined as cycle 1 hematologic toxicity grade ≥ 3 not resolving to grade ≤ 1 within 1 week or non-hematologic toxicity grade ≥ 3 (except controlled nausea and vomiting and transient liver function abnormalities) attributable to belinostat. RESULTS: Among 51 patients, two DLTs were observed: grade 3 hypersensitivity with dizziness and hypoxia at 1700 mg/m2/day belinostat with 100 mg/m2/day 13-cRA, and grade 3 allergic reaction at 2000 mg/m2/day belinostat with 100 mg/m2/day 13-cRA. The MTD was not reached. Pharmacokinetics of belinostat may be non-linear at high doses. Ten patients had stable disease, including one with neuroendocrine pancreatic cancer for 56 cycles, one with breast cancer for 12 cycles, and one with lung cancer for 8 cycles. Partial responses included a patient with keratinizing squamous cell carcinoma of the tonsils, and a patient with lung cancer. CONCLUSIONS: The combination of belinostat 2000 mg/m2 days 1-5 and 13-cRA 100 mg/m2 days 1-14, every 21 days, was well-tolerated and an MTD was not reached despite doubling the established single-agent MTD of belinostat.

The application of the improved 3D rat testicular cells co-culture model on the in vitro toxicity research of HZ1006.

The aims of the present research are to further validate the application of the improved three-dimensional (3 D) rat testicular cell co-culture model to evaluate the effects of various reprotoxic chemicals on the function of the main somatic cells, as well as on spermatogonial cell differentiation and even spermatogenesis, and to investigate the specific toxicant mechanisms in testes treated with HZ1006, a hydroxamate-based a hydroxamate-based histone deacetylase inhibitor (HDACI). Based on the characteristics of HZ1006, the appropriate exposure duration (8, 16, or 24 days), dosage (0, 3.125, 6.25, 12.5, or 25 µM) and toxic endpoints suitable for detection were selected in the experiments. The results showed inhibition of cell proliferation, reduced testosterone levels, and decreased spermatogonial cell meiosis-specific gene expression, as well as decreased protein levels of androgen receptor (AR) and decreased expression of the AR target gene PSA, accompanied by inhibition of Hdac6 expression after HZ1006 exposure in the 3 D rat testicular cell co-culture model. These findings indicate that the improved 3 D rat testicular cell co-culture model we have established has the potential to become a new testicular toxicity test system that can be used to test toxic characteristics and mechanisms of new compounds and has good application prospects, although more research on the model is required.

Investigation of belinostat-induced genomic instability by molecular cytogenetic analysis and pathway-focused gene expression profiling.

Histone deacetylases (HDACs), which regulate transcription and specific functions such as tumor suppression by p53, are frequently altered in tumors and have a contentious role in carcinogenesis. HDAC inhibitors, which have a long history of use in psychiatry and neurology, have recently been tested as possible treatments for tumors. Belinostat received regulatory approval in the USA on July 3, 2014, for use against peripheral T-cell lymphoma. However, the unavailability of information on belinostat genotoxicity in normal cells and the molecular mechanisms involved in the genetic instability after exposure to belinostat encouraged us to conduct this study. Our data showed that the exposure of mice to belinostat at the recommended human doses induced chromosome breakage, whole-chromosome lagging, and oxidative DNA damage in bone marrow cells in a dose-dependent manner. The expression levels of 84 genes involved in the DNA damage signaling pathway were evaluated by using an RT2 Profiler PCR array. Belinostat exposure altered the expression of 25 genes, with statistically significant changes observed in 17 genes. The array results were supported by RT-PCR and western blotting experiments. Collectively, our results showed that belinostat exposure caused oxidative DNA damage and downregulated the expression of genes involved in DNA damage repair, which may be responsible for belinostat-induced genomic instability. Thus, the clinical usage of this drug should be weighed against the hazards of carcinogenesis, and the observed genotoxicity profile of belinostat may support further development of efficient HDAC inhibitors with weaker genotoxicity.

Marbostat-100 Defines a New Class of Potent and Selective Antiinflammatory and Antirheumatic Histone Deacetylase 6 Inhibitors.

Epigenetic modifiers of the histone deacetylase (HDAC) family contribute to autoimmunity, cancer, HIV infection, inflammation, and neurodegeneration. Hence, histone deacetylase inhibitors (HDACi), which alter protein acetylation, gene expression patterns, and cell fate decisions, represent promising new drugs for the therapy of these diseases. Whereas pan-HDACi inhibit all 11 Zn2+-dependent histone deacetylases (HDACs) and cause a broad spectrum of side effects, specific inhibitors of histone deacetylase 6 (HDAC6i) are supposed to have less side effects. We present the synthesis and biological evaluation of Marbostats, novel HDAC6i that contain the hydroxamic acid moiety linked to tetrahydro-ß-carboline derivatives. Our lead compound Marbostat-100 is a more potent and more selective HDAC6i than previously established well-characterized compounds in vitro as well as in cells. Moreover, Marbostat-100 is well tolerated by mice and effective against collagen type II induced arthritis. Thus, Marbostat-100 represents a most selective known HDAC6i and the possibility for clinical evaluation of a HDAC isoform-specific drug.

Discovery of benzo[g]indoles as a novel class of non-covalent Keap1-Nrf2 protein-protein interaction inhibitor.

The Keap1-Nrf2 system is an attractive target for drug discovery regarding various unmet medical needs. Only covalent inhibitors for protein-protein interaction (PPI) between Keap1 and Nrf2 to activate Nrf2 have been approved or are under clinical trials, but such electrophilic compounds lack selectivity. Therefore, specific non-covalent Keap1-Nrf2 PPI inhibitors are expected to be safer Nrf2 activators. We found a novel class of non-covalent Keap1-Nrf2 PPI inhibitor that has a benzo[g]indole skeleton and an indole-3-hydroxamic acid moiety and that exhibits significant PPI inhibitory activity. Additionally, the benzo[g]indole-3-carbohydrazide derivatives were newly prepared. The benzo[g]indole derivatives showed a stronger Keap1-Nrf2 PPI inhibitory activity than Cpd16, a previously reported non-covalent PPI inhibitor. Moreover, most of the PPI inhibitors showed a high metabolic stability in a human microsome system with a low cytotoxicity against HepG2 cell lines, which suggests that novel benzo[g]indole-type Keap1-Nrf2 PPI inhibitors are expected to be biological tools or lead compounds for Nrf2 activators.

Combined use of irinotecan with histone deacetylase inhibitor belinostat could cause severe toxicity by inhibiting SN-38 glucuronidation via UGT1A1.

SN-38, the active metabolite of irinotecan, and histone deacetylase inhibitors (HDACis) such as belinostat, vorinostat and panobinostat, have all been shown to be deactivated by glucuronidation via UGTs. Since they all compete for UGTs for deactivation, we aimed to investigate the inhibitory effect of various HDACis on the glucuronidation of SN-38. This inhibitory effect was determined by measuring the formation rate of SN-38 glucuronide after SN-38 incubation with human recombinant UGT1A isoforms (1A1, 1A6, 1A7 and 1A9) and pooled human liver microsomes (HLM, wild type, UGT1A1*1*28 and UGT1A1*28*28 allelic variants), with and without HDACis. The data showed that belinostat at 100 and 200 µmol/L inhibited SN-38 glucuronidation via UGT1A1 in a dose-dependent manner, causing significant decrease in Vmax and CLint (p < 0.05) from 12.60 to 1.95 pmol/min/mg and 21.59 to 4.20 µL/min/mg protein respectively. Similarly, in HLMs, Vmax dropped from 41.13 to 10.54, 24.96 to 3.77 and 6.23 to 3.30 pmol/min/mg, and CLint reduced from 81.25 to 26.11, 29.22 to 6.10 and 5.40 to 1.34 µL/min/mg protein for the respective wild type, heterozygous and homozygous variants. Interestingly, belinostat at 200 µmol/L that is roughly equivalent to the average Cmax, 183 µmol/L of belinostat at a dose of 1,400 mg/m2 given intravenously once per day on days 1 to 5 every 3 weeks, was able to inhibit both heterozygous and homozygous variants to same extents (~64%). This highlights the potential clinical significance, as a large proportion of patients could be at risk of developing severe toxicity if irinotecan is co-administered with belinostat.

Metabolic changes in rat serum after administration of suberoylanilide hydroxamic acid and discriminated by SVM.

Suberoylanilide hydroxamic acid (SAHA) exerts marked anticancer effects via promotion of apoptosis, cell cycle arrest, and prevention of oncogene expression. In this study, serum metabolomics and artificial intelligence recognition were used to investigate SAHA toxicity. Forty rats (220 ± 20 g) were randomly divided into control and three SAHA groups (low, medium, and high); the experimental groups were treated with 12.3, 24.5, or 49.0 mg kg-1 SAHA once a day via intragastric administration. After 7 days, blood samples from the four groups were collected and analyzed by gas chromatography-mass spectrometry, and pathological changes in the liver were examined using microscopy. The results showed that increased levels of urea, oleic acid, and glutaconic acid were the most significant indicators of toxicity. Octadecanoic acid, pentadecanoic acid, glycerol, propanoic acid, and uric acid levels were lower in the high SAHA group. Microscopic observation revealed no obvious damage to the liver. Based on these data, a support vector machine (SVM) discrimination model was established that recognized the metabolic changes in the three SAHA groups and the control group with 100% accuracy. In conclusion, the main toxicity caused by SAHA was due to excessive metabolism of saturated fatty acids, which could be recognized by an SVM model.

Chronic drug-induced effects on contractile motion properties and cardiac biomarkers in human induced pluripotent stem cell-derived cardiomyocytes.

BACKGROUND AND PURPOSE: In the pharmaceutical industry risk assessments of chronic cardiac safety liabilities are mostly performed during late stages of preclinical drug development using in vivo animal models. Here, we explored the potential of human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs) to detect chronic cardiac risks such as drug-induced cardiomyocyte toxicity. EXPERIMENTAL APPROACH: Video microscopy-based motion field imaging was applied to evaluate the chronic effect (over 72 h) of cardiotoxic drugs on the contractile motion of hiPS-CMs. In parallel, the release of cardiac troponin I (cTnI), heart fatty acid binding protein (FABP3) and N-terminal pro-brain natriuretic peptide (NT-proBNP) was analysed from cell medium, and transcriptional profiling of hiPS-CMs was done at the end of the experiment. KEY RESULTS: Different cardiotoxic drugs altered the contractile motion properties of hiPS-CMs together with increasing the release of cardiac biomarkers. FABP3 and cTnI were shown to be potential surrogates to predict cardiotoxicity in hiPS-CMs, whereas NT-proBNP seemed to be a less valuable biomarker. Furthermore, drug-induced cardiotoxicity produced by chronic exposure of hiPS-CMs to arsenic trioxide, doxorubicin or panobinostat was associated with different profiles of changes in contractile parameters, biomarker release and transcriptional expression. CONCLUSION AND IMPLICATIONS: We have shown that a parallel assessment of motion field imaging-derived contractile properties, release of biomarkers and transcriptional changes can detect diverse mechanisms of chronic drug-induced cardiac liabilities in hiPS-CMs. Hence, hiPS-CMs could potentially improve and accelerate cardiovascular de-risking of compounds at earlier stages of drug discovery. LINKED ARTICLES: This article is part of a themed section on New Insights into Cardiotoxicity Caused by Chemotherapeutic Agents. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.21/issuetoc.

Design, synthesis and evaluation of antiproliferative activity of melanoma-targeted histone deacetylase inhibitors.

The clinical validation of histone deacetylase inhibition as a cancer therapeutic modality has stimulated interest in the development of new generation of potent and tumor selective histone deacetylase inhibitors (HDACi). With the goal of selective delivery of the HDACi to melanoma cells, we incorporated the benzamide, a high affinity melanin-binding template, into the design of HDACi to generate a new series of compounds 10a-b and 11a-b which display high potency towards HDAC1 and HDAC6. However, these compounds have attenuated antiproliferative activities relative to the untargeted HDACi. An alternative strategy furnished compound 14, a prodrug bearing the benzamide template linked via a labile bond to a hydroxamate-based HDACi. This pro-drug compound showed promising antiproliferative activity and warrant further study.

Enhanced in vitro cytotoxicity and anti-tumor activity of vorinostat-loaded pluronic micelles with prolonged release and reduced hepatic and renal toxicities.

Vorinostat is the first histone deacetylase inhibitor approved by US FDA for use in cancer therapy. However, its limited aqueous solubility, low permeability, and suboptimal pharmacokinetics hinder its delivery. Thus, in this study, micelles of vorinostat with each of pluronic F68 (PF68) and pluronic F127 (PF127) were developed and optimized based on drug loading and entrapment. The optimized micelles were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), differential scanning calorimetry (DSC), zeta analyzer, and electron transmission microscopy. Their in vitro release, stability, in vitro cytotoxicity against HepG2, Caco-2, and MCF-7 cell lines, and finally, in vivo antitumor activity in mice bearing Ehrlich Ascites Carcinoma (EAC) were assessed. The highest entrapment efficiency was 99.09±2.16% and 94.19±2.37% for micelles of 1:50 drug to polymer ratio with each of PF127 and PF68, respectively. These micelles were nearly spherical with nanoscopic mean diameters of 72.61±10.66nm for PF68 and 91.88±10.70nm for PF127 with narrow size distribution. The micelles provided prolonged release at phosphate buffer saline pH7.4 up to 24h for PF68 and 72h for PF127. Potentiation of in vitro cytotoxicity of vorinostat was more pronounced with PF127 micelles particularly against MCF-7 cells. Compared with free vorinostat, the micelles with PF127 were more effective in inhibiting tumor growth as well as exhibiting significantly (p<0.05) diminished hepatic and renal toxicities. In conclusion, 1:50 vorinostat-PF127 micelles may facilitate i.v. formulations and can be suggested as a promising stable and safe nanoparticulate delivery system with prolonged release and potentiated cytotoxicity.

Subchronic Toxicities of HZ1006, a Hydroxamate-Based Histone Deacetylase Inhibitor, in Beagle Dogs and Sprague-Dawley Rats.

Histone deacetylase inhibitors (HDACIs), such as vorinostat and panobinostat, have been shown to have active effects on many hematologic malignancies, including multiple myeloma and cutaneous T-cell lymphoma. Hydroxamate-based (Hb) HDACIs have very good toxicity profiles and are currently being tested in phases I and II clinical trials with promising results in selected neoplasms, such as bladder carcinoma. One of the Hb-HDACIs, HZ1006, has been demonstrated to be a promising drug for clinical use. The aim of our study was to determine the possible target of toxicity and to identify a non-toxic dose of HZ1006 for clinical use. In our studies, the repeated dosage toxicity of HZ1006 in Beagle dogs and Sprague Dawley (SD) rats was identified. Dogs and rats received HZ1006 orally (0-80 and 0-120 mg/kg/day, respectively) on a continuous daily dosing agenda for 28 days following a 14-day dosage-free period. HZ1006's NOAEL (No Observed Adverse Effect Level) by daily oral administration for dogs and rats was 5 mg/kg and 60 mg/kg, respectively, and the minimum toxic dose was 20 and 120 mg/kg, respectively. All the side effects indicated that the digestive tract, the male reproductive tract, the respiratory tract and the hematological systems might be HZ1006 toxic targets in humans. HZ1006 could be a good candidate or a safe succedaneum to other existing HDACIs for the treatment of some solid tumor and hematologic malignancies.

Bortezomib, thalidomide, dexamethasone, and panobinostat for patients with relapsed multiple myeloma (MUK-six): a multicentre, open-label, phase 1/2 trial.

BACKGROUND: Panobinostat (a pan histone deacetylase inhibitor) is approved in combination with bortezomib and dexamethasone for patients with relapsed multiple myeloma who have received two or more previous lines of therapy. We aimed to improve the safety of this combination and investigate efficacy by incorporating low-dose thalidomide, using sub-cutaneous weekly bortezomib, and determining the maximum tolerated dose of panobinostat in this regimen. METHODS: We did a phase 1/2, multicentre, open-label trial (MUK six) at four hospitals in the UK, enrolling patients with relapsed, or relapsed and refractory, multiple myeloma aged at least 18 years, with an Eastern Cooperative Oncology Group performance status of 2 or less who had previously received 1-4 lines of therapy. Exclusion criteria included any antimyeloma treatment within 28 days of study drugs (except dexamethasone 160 mg >48 h before treatment). We used a rolling six escalation design to determine the maximum tolerated dose of panobinostat, and allocated patients to receive subcutaneous bortezomib 1·3 mg/m2, and oral thalidomide 100 mg, dexamethasone 20 mg, and panobinostat 10, 15, or 20 mg (escalated to 20 mg according to the escalation schedule). Treatment was given during a 21-day cycle (bortezomib on days 1 and 8; thalidomide every day; dexamethasone on days 1, 2, 8, and 9; and panobinostat on days 1, 3, 5, 8, 10, and 12) for 16 cycles in the absence of disease progression or unacceptable toxicity. Patients were permitted to come off study for autologous stem cell transplantation. The primary objective was to determine the maximum tolerated dose and recommended dose of panobinostat, and to estimate the proportion of patients with an overall response that was equal to a partial response or greater within 16 cycles of treatment at the recommended panobinostat dose in the modified intention-to-treat population. We assessed safety in all patients who received a trial drug (ie, bortezomib, thalidomide, dexamethasone, or panobinostat). This trial is registered at ClinicalTrials.gov, number NCT02145715, and with the ISRCTN registry, number ISRCTN59395590 and is closed to recruitment. FINDINGS: Between Jan 31, 2013, and Oct 30, 2014, we enrolled 57 eligible patients who received at least one dose of trial medication or any drug. One dose-limiting toxicity was reported (grade 3 hyponatremia at the 20 mg dose), therefore the maximum tolerated dose was not reached, and 20 mg was deemed to be the recommended dose. 46 patients were treated with panobinostat 20 mg (the intention-to-treat population). 42 patients (91%, 80% CI 83·4-96·2) of 46 achieved the primary endpoint of an overall response that was equal to a partial response or greater. Most adverse events were grade 1-2 with few occurrences of grade 3-4 diarrhoea or fatigue. The most common adverse events of grade 3 or worse in the safety population (n=57) were reduced neutrophil count (15 [26%]), hypophosphatemia (11 [19%]), and decreased platelet count (8 [14%]). 46 serious adverse events were reported in 27 patients; of 14 suspected to be related to the trial medication, seven (50%) were gastrointestinal disorders. INTERPRETATION: Panobinostat 20 mg in combination with bortezomib, thalidomide, and dexamethasone is an efficacious and well tolerated regimen for patients with relapsed multiple myeloma. FUNDING: Novartis and Myeloma UK.

Epigenetic mutagen as histone modulator can be detected by yeast flocculation.

We have previously reported that flocculation of a yeast co-transformed with the human DNA methyltransferase 1 (DNMT1) and DNMT3B genes was inhibited by DNMT inhibitors. It is well known that epigenetic mutagens can disturb nucleosome positioning via DNA methylation and/or histone modification. In this study we first examined the effects of trichostatin A (TSA), a histone deacetylase inhibitor, on the flocculation level of yeast. TSA dose-dependently promoted the flocculation exhibited by the yeast transformed with the DNMT genes or empty vectors. Furthermore, TSA induced the expression of the flocculin-encoding gene FLO1 The anthracene-derived alizarin, a natural madder root dye, has a potential for carcinogenesis promotion; however, the mode of action has not been elucidated. It is considered that epigenetic changes can promote cancer. Alizarin but not anthracene enhanced the flocculation level of the yeast. Similar to TSA, alizarin also upregulated FLO1 mRNA. Surprisingly, western blotting indicated that alizarin, but not anthracene, reduced the level of histone H3 in yeast, and alizarin-treated cells frequently displayed abnormally shaped nuclei. These findings suggest that alizarin uniquely influences nucleosome structure. Taken together with our previous findings, this study suggests that the DNMT gene-transformed yeast strains are a useful tool for screening various classes of epigenetic mutagens.

An appraisal of cinnamyl sulfonamide hydroxamate derivatives (HDAC inhibitors) for anti-cancer, anti-angiogenic and anti-metastatic activities in human cancer cells.

Multiple genetic mutations along with unusual epigenetic modifications play a major role in cancer development. Histone deacetylase (HDAC) enzyme overexpression observed in the majority of cancers is responsible for tumor suppressor gene silencing and activation of proto-oncogenes to oncogenes. Cinnamic acid derivatives exhibit anti-cancer potential through HDAC enzyme inhibition. We have synthesized a few cinnamyl sulfonamide hydroxamate derivatives (NMJ-1, -2 and -3) by already published in-house procedures and their purity, and chemical characterization were performed by NMR, mass spectrometry and elemental analysis. The anti-cancer activities were also evaluated against colon cancer. The rationale for synthesis was based on bioisosterism concept. To take the work forward, these compounds were considered for in vitro anti-angiogenic and anti-metastatic activities in cancer cells. The effectiveness of these compounds was determined by SRB assay. The compounds showed cancer cell cytotoxicity (IC50 range of 5.7 ± 0.43 to 20.5 ± 1.9 µM). The mechanism of compound-induced cell death involves an intrinsic apoptosis pathway which was supported by the following: increase in apoptotic index, arrest in cell cycle at G2/M phase, increase in annexin V binding and induction of p21(Waf1/Cip1) expression in the treated cells. Further, their target modulating effect, measured as the expression of acetyl-H3 histone and acetyl α-tubulin was determined by Western blots. Hyper acetylation of H3 histone and α-tubulin were observed. Furthermore, increased expression of cleaved caspase-3, cleaved PARP, total Bad was estimated by ELISA. The anti-angiogenic effect was examined through cobalt (II) chloride (CoCl2)-induced HIF-1α expression, where the compounds reduced the expression of induced HIF-1α. In addition, their anti-metastatic ability was determined through phorbol-12-myristate-13-acetate (PMA)-induced expression of MMP-2 and -9 by Western blotting and gelatin zymography. Inhibition of malignant cell migration was assessed by scratch wound assay. The compounds showed a decrease in cell migration and inhibition of induced MMP-2 and MMP-9 expression. NMJ-2 exhibited comparable activity to that of standard SAHA. Our findings indicate that NMJ series of compound have potent in vitro anti-cancer, anti-angiogenic and anti-metastatic activity through HDAC enzyme inhibition.

Knockdown of Rad9A enhanced DNA damage induced by trichostatin A in esophageal cancer cells.

Histone deacetylase (HDAC) inhibitors have recently emerged as a new class of anticancer agents. As a classical HDAC inhibitor, trichostatin A (TSA) has been shown to possess many anticancer activities such as induction of cell cycle arrest, promotion of cell death, and enhancement of radiosensitity. In our previous work, we found that TSA treatment induced Rad9 gene expression, which suggested that Rad9 might play a role in TSA-induced biological effects. As Rad9 is involved in maintaining genomic integrity, we further analyzed the DNA damage induced by TSA and combined with Rad9 knockdown in esophageal cancer cells (ESCCs). Our results showed that TSA treatment alone induced significantly DNA damage in ESCC cells. Simultaneously, TSA also induced Rad9 gene expression both at transcriptional and translational levels in EC109 cells, but not in KYSE150 cells. Further, the induction of Rad9 by TSA was accompanied with increased level of histone H3K9 acetylation in Rad9 promoter region. To understand the role of Rad9 in TSA-induced DNA damage, Rad9 gene expression was efficiently knocked down by small interfering RNA (siRNA), which led to enhanced DNA damage and cell death induced by TSA. Our data suggested that Rad9 plays an important role in DNA damage, which is related to the biological effects of TSA.