Potent Histone Deacetylase Inhibitory Activity Research Articles

Lysines Acetylome and Methylome Profiling of H3 and H4 Histones in Trichostatin A-Treated Stem Cells.

Trichostatin A ([R-(E,E)]-7-[4-(dimethylamino) phenyl]-N-hydroxy- 4,6-dimethyl- 7-oxo-2,4-heptadienamide, TSA) affects chromatin state through its potent histone deacetylase inhibitory activity. Interfering with the removal of acetyl groups from lysine residues in histones is one of many epigenetic regulatory processes that control gene expression. Histone deacetylase inhibition drives cells toward the differentiation stage, favoring the activation of specific genes. In this paper, we investigated the effects of TSA on H3 and H4 lysine acetylome and methylome profiling in mice embryonic stem cells (ES14), treated with trichostatin A (TSA) by using a new, untargeted approach, consisting of trypsin-limited proteolysis experiments coupled with MALDI-MS and LC-MS/MS analyses. The method was firstly set up on standard chicken core histones to probe the optimized conditions in terms of enzyme:substrate (E:S) ratio and time of proteolysis and, then, applied to investigate the global variations of the acetylation and methylation state of lysine residues of H3 and H4 histone in the embryonic stem cells (ES14) stimulated by TSA and addressed to differentiation. The proposed strategy was found in its simplicity to be extremely effective in achieving the identification and relative quantification of some of the most significant epigenetic modifications, such as acetylation and lysine methylation. Therefore, we believe that it can be used with equal success in wider studies concerning the characterization of all epigenetic modifications.

Novel 4-Oxoquinazoline-Based N-Hydroxypropenamides as Histone Deacetylase Inhibitors: Design, Synthesis, and Biological Evaluation.

Two series of novel 4-oxoquinazoline-based N-hydroxypropenamides (9a–m and 10a–m) were designed, synthesized, and evaluated for their inhibitory and cytotoxicity activities against histone deacetylase (HDAC). The compounds showed good to potent HDAC inhibitory activity and cytotoxicity against three human cancer cell lines (SW620, colon; PC-3, prostate; NCI-H23, lung cancer). In this series, compounds with the N-hydroxypropenamide functionality impeded at position 7 on the 4-oxoquinazoline skeleton (10a–m) were generally more potent than compounds with the N-hydroxypropenamide moiety at position 6 (9a–m). Also, the N3-benzyl-substituted derivatives (9h–m, 10h–m) exhibited stronger bioactivity than the N3-alkyl-substituted ones (9a–e, 10a–e). Two compounds 10l and 10m were the most potent ones. Their HDAC inhibitory activity (IC50 values, 0.041–0.044 μM) and cytotoxicity (IC50 values, 0.671–1.211 μM) were approximately 2- to 3-fold more potent than suberoylanilide hydroxamic acid (SAHA). Some compounds showed up to 10-fold more potent HDAC6 inhibition compared to their inhibitory activity in total HDAC extract assay. Analysis of selected compounds 10l and 10m revealed that these compounds strongly induced both early and late apoptosis and arrested SW620 cells at the G2/M phase. Docking studies were carried out on the HDAC6 isoform for series 10a–m and revealed some important features contributing to the inhibitory activity of synthesized compounds.

Design, synthesis and biological evaluation of novel HDAC inhibitors with improved pharmacokinetic profile in breast cancer

The dysfunction of histone deacetylase (HDACs) is closely related to tumorigenesis and development, which has been emerged as an attractive drug design target for cancer therapy. In the present study, we designed and synthesized a series of novel HDAC inhibitors using a substituted quinazoline as the capping group and attaching 3, 5-dimethylbenyl as a potential metabolic site protector. 23g and 23h were demonstrated potent HDAC inhibitory activities and anti-proliferative effects against MDA-MB-231cells. In addition, 23g and 23h both could significantly increase the acetylation level of intracellular proteins, especially in α-Tubulin and HSP90. 23g and 23h displayed a slight different anti-tumor mechanism, 23g mainly induced apoptosis while 23h induced obviously ER-Stress. Furthermore, 23g and 23h both induced autophagy and migration inhibition. In pharmacokinetics assay, 23g showed a significant improvement of pharmacokinetic profile for oral administration. Additionally, 23g presented more potent anti-proliferation and anti-migration activity than SAHA in zebrafish MDA-MB-231cell line-derived xenograft model. Together, these results demonstrate that 23g is a novel oral HDAC inhibitor with a potential capacity of treating breast cancer.

Design, synthesis and biological evaluation of coumarin-based N-hydroxycinnamamide derivatives as novel histone deacetylase inhibitors with anticancer activities

A series of novel coumarin-based N-hydroxycinnamamide derivatives were designed and synthesized as histone deacetylase (HDAC) inhibitors. Most of the synthesized compounds showed potent HDAC inhibitory activity and significant antiproliferative activity against human cancer cell lines MCF-7, HepG2, HeLa and HCT-116. Among them, compound 14f displayed the most potent HDAC inhibition, especially against HDAC1 with IC50 value of 0.19 μM, which was better than that of SAHA (IC50 = 0.23 μM). It also showed the strongest antiproliferative activity towards HeLa cells and more than 26-fold selectivity for HDAC1 compared with HDAC6. Molecular docking studies revealed the possible binding modes of compound 14f into the two isoforms and provided a reasonable explanation for the selectivity. In addition, compound 14f could inhibit colony formation, upregulate the acetylation level of histone H3, and induce apoptosis and cell cycle arrest at G2/M phase in HeLa cells. Taken together, these results highlighted that compound 14f might be a promising HDAC inhibitor for cancer therapy.

N-alkyl-hydroxybenzoyl anilide hydroxamates as dual inhibitors of HDAC and HSP90, downregulating IFN-γ induced PD-L1 expression

Novel dual inhibitors of histone deacetylase (HDAC) and heat-shock protein 90 (HSP90) are synthesized and evaluated. These compounds are endowed with potent HDAC and HSP90 inhibitory activities with IC50 values in nanomolar range with Compound 20 (HDAC IC50 = 194 nM; HSP90α IC50 = 153 nM) and compound 26 (HDAC IC50 = 360 nM; HSP90α IC50 = 77 nM) displaying most potent HDAC and HSP90α inhibitory activities. Both of these compounds induce HSP70 expression and down regulate HSP90 client proteins which play important roles in the regulation of survival and invasiveness in cancer cells. In addition, compounds 20 and 26 induce acetylation of α-tubulin and histone H3. Significantly, compounds 20 and 26 could effectively reduce programmed death-ligand 1 (PD-L1) expression in IFN-γ treated lung H1975 cells in a dose dependent manner. These findings suggest that dual inhibition of HDAC and HSP90 that can modulate immunosuppressive ability of tumor area may provide a better therapeutic strategy for cancer treatment in the future.

Thioether-based 2-aminobenzamide derivatives: Novel HDAC inhibitors with potent in vitro and in vivo antitumor activity

Previously, we focused on a series of 2-aminobenzamide-based histone deacetylase (HDAC) inhibitors, compound 9 of which displayed potent HDAC inhibitory activity against HDAC1 and HDAC2, and moderate anti-proliferative activity against several cancer cell lines. In the current study, we have designed and synthesized a series of novel HDAC inhibitors based on thioether moiety with 9 as a lead compound. Representative compounds12 g and 12 h showed apparently potent anti-proliferative activities against five solid cancer cell lines: A549, HCT116, Hela, A375 and SMMC7721, and low cytotoxicity against NIH 3T3 normal cells. Especially, 12 g and 12 h also revealed potent HDAC inhibitory activity against HDAC1, 2 and 3. In addition, the two compounds could arrest cell cycle in G2/M phase and promote cell apoptosis. Moreover, they showed extended inhibition of colony formation and effectively blocked cell migration towards A549 cancer cells. Furthermore, 12 g and 12 h possessed better pharmacokinetic properties than the lead compound 9. Benefiting from these results, we also explored 12 g and 12 h in the A549 xenografts model for in vivo antitumor activity. The in vivo experiment indicated that 12 g and 12 h could evidently augment antitumor activity (TGI = 56.9% and 62.7% respectively).

Design, synthesis, and biological evaluation of histone deacetylase inhibitors possessing glutathione peroxidase-like and antioxidant activities against Alzheimer's disease.

A series of hybrids containing the pharmacophores of the histone deacetylase (HDAC) inhibitor, SAHA, and the antioxidant ebselen were designed and synthesized as multi-target-directed ligands against Alzheimer's disease. An in vitro assay indicated that some of these molecules exhibit potent HDAC inhibitory activity and ebselen-related pharmacological effects. Specifically, the optimal compound 7f was found to be a potent HDAC inhibitor (IC50 = 0.037 μM), possessing rapid hydrogen peroxide scavenging activity and glutathione peroxidase-like activity (ν0 = 150.0 μM min-1) and good free oxygen radical absorbance capacity (value of ORAC: 2.2). Furthermore, compound 7f showed significant protective effects against damage induced by H2O2 and the ability to prevent ROS accumulation in PC12 cells.

Design and synthesis of tranylcypromine derivatives as novel LSD1/HDACs dual inhibitors for cancer treatment

Lysine specific demethylase 1 (LSD1) and Histone deacetylases (HDACs) are promising drug targets for cancers. Recent studies reveal an important functional interplay between LSD1 and HDACs, and there is evidence for the synergistic effect of combined LSD1 and HDAC inhibitors on cancers. Therefore, development of inhibitors targeting both LSD1 and HDACs might be a promising strategy for epigenetic therapy of cancers. We report herein the synthesis of a series of tranylcypromine derivatives as LSD1/HDACs dual inhibitors. Most compounds showed potent LSD1 and HDACs inhibitory activity, especially compound 7 displayed the most potent inhibitory activity against HDAC1 and HDAC2 with IC50 of 15 nM and 23 nM, as well as potent inhibition against LSD1 with IC50 of 1.20 μM. Compound 7 demonstrated stronger anti-proliferative activities than SAHA with IC50 values ranging from 0.81 to 4.28 μM against MGC-803, MCF-7, SW-620 and A-549 human cancer cell lines. Further mechanistic studies showed that compound 7 treatment in MGC-803 cells dose-dependently increased cellular H3K4 and H3K9 methylation, as well as H3 acetylation, decreased the mitochondrial membrane potential and induced remarkable apoptosis. Docking studies showed that compound 7 can be well docked into the active binding sites of LSD1 and HDAC2. This finding highlights the potential for the development of LSD1/HDACs dual inhibitors as novel anticancer drugs.

Design, synthesis, and preliminary bioactivity evaluation of N-benzylpyrimidin-2-amine derivatives as novel histone deacetylase inhibitor.

Histone deacetylase (HDAC) inhibitors have been identified for the treatment of cancer. Lately, we designed and synthesized a series of substituted N-benzylpyrimidin-2-amine derivatives as potent HDAC inhibitors. In vitro HDAC inhibitory activities and antiproliferative activities of target compounds were investigated. Some target compounds showed potent HDAC inhibitory activities and possessed obvious antiproliferative activity against tumor cells. Target compounds 6a, 6d, 8a, 8c, and 8f not only exhibited almost equally enzymatic inhibitory activity with SAHA, but showed better antiproliferative activities.

Design, synthesis and anticancer potential of NSC-319745 hydroxamic acid derivatives as DNMT and HDAC inhibitors

DNA methyltransferases (DNMTs) and histone deacetylases (HDACs) are important epigenetic targets during anticancer drug development. Recent study indicates that DNMT inhibitors and HDAC inhibitors display synergistic effects in certain cancers, therefore, development of molecules targeting both DNMT and HDAC is of therapeutic advantage against these cancers. Based on the structure of DNMT inhibitor NSC-319745 and the pharmacophore characteristics of HDAC inhibitors, a series of hydroxamic acid derivatives of NSC-319745 were designed and synthesized as DNMT and HDAC multifunctional inhibitors. Most compounds displayed potential DNMT inhibitory potency and potent HDAC inhibitory activity, especially compound 15a showed much better DNMT1 inhibitory potency than NSC-319745, and inhibited HDAC1, HDAC6 with IC50 values of 57, 17 nM, respectively. Furthermore, the synthesized compounds exhibited significant cytotoxicity against human cancer cells K562 and U937. Further mechanistic studies demonstrated that 15a treatment in U937 increased histones H3K9 and H4K8 acetylation, prompted P16 CpG islands demethylation and upregulated P16 expression, regulated apoptosis-related protein expression on the cellular level and induced remarkable U937 apoptosis. Moreover, genotoxicity of representative compounds was evaluated. In summary, our study provided a practical drug design strategy targeting multiple enzymes, and 15a represents a novel and promising lead compound for the development of novel epigenetic inhibitors as antitumor agents.

Design, synthesis and biological evaluation of novel hydroxamates and 2-aminobenzamides as potent histone deacetylase inhibitors and antitumor agents

Many studies have indicated that histone deacetylase (HDAC) inhibitors are promising agents for the treatment of cancer. With the aim to search for novel potent HDAC inhibitors, we designed and synthesized two series of hydroxamates and 2-aminobenzamides compounds as HDAC inhibitors and antitumor agents. Those compounds were investigated for their HDAC enzymatic inhibitory activities and in vitro anti-proliferation activities against diverse cancer cell line (A549, HepG2, MGC80-3 and HCT116). Most of the synthesized compounds displayed potent HDAC inhibitory activity and antiproliferative activity. In particular, Compound 12a, N-(2-aminophenyl)-4-[(4-fluorophenoxy)methyl]benzamide, was shown to have the most HDAC inhibitory activity (70.6% inhibition at 5 μM) and antitumor activity with IC50 value of as low as 3.84 μM against HepG2 human liver hepatocellular carcinoma cell line, more than 4.8–fold lower than CS055 and 5.9–fold lower than CI994. HDAC isoform selectivity assay indicated 12a is a potent HDAC2 inhibitor. Docking study of 12a suggested that it bound tightly to the binding pocket of HDAC2. Further investigation showed that 12a could inhibit the migration and colony formation of A549 cancer cells. Furthermore, 12a remarkably induced apoptosis and G2/M phase cell cycle arrest in A549 cancer cells. Those results indicated that compound 12a could be a promising candidate for treatment of cancer.

Indole-3-ethylsulfamoylphenylacrylamides with Potent Anti-proliferative and Anti-angiogenic Activities.

HDAC inhibition is emerging as a new strategy for cancer therapy. We previously reported that Nhydroxy- 3-{4-[2-(2-methyl-1H-indol-3-yl)-ethylsulfamoyl]-phenyl}-acrylamide (9) demonstrated potent histone deacetylases (HDAC) inhibition and anti-inflammatory effects. This continuous study provides detailed structureactivity relationship (SAR) of novel indol-3-ethylsulfamoylphenylacrylamides as anti-cancer agents. These compounds are endowed with potent HDAC inhibitory activity, almost 2.5 folds to 42 folds better than suberanilohydroxamic acid (SAHA). Compounds 8, 10, 11 and 17 exhibited significant inhibitory effects on various cancer cell lines with GI50 values in the range of 0.02 to 0.35 μM which are 10-50 folds better than SAHA. In-vivo nude mice model indicated the anti-angiogenic potential of these acrylamides. This study has indicated the potential of 3-{4-[2-(1-Ethyl-2-methyl-1H-indol-3-yl)-ethyl-N-tert-butoxycarbonylsulfamoyl]-phenyl}-N-hydroxy-acrylamide (11, mean GI50 = 0.04 μM) as a lead molecule for further development as anti-cancer agent.

Design, synthesis and biological evaluation of saccharin-based N-hydroxybenzamides as histone deacetylases (HDACs) inhibitors

We report the development of a novel series of saccharin-based N-hydroxybenzamides as histone deacetylases inhibitors. Among them, 6j exhibited potent HDACs inhibitory activity against Hela nuclear extract. Further biological evaluation found 6i showed similar antiproliferative activities in vitro compared with the approved SAHA.

Abstract 3736: Application of patient tumors-derived tumor ecosystem platform for the development of novel HDAC inhibitor in solid cancers

Abstract Histone deacetylases (HDAC) are deregulated in many human cancers and a few HDAC inhibitors (HDACi) have been shown to be effective in patients with rare leukemia. However, clinical responses are not very promising for many HDACi in solid cancers. There is an urgent need to develop best in class HDACi with higher therapeutic index in solid cancers. At present less than 10% of anti-cancer drugs entering phase 1 clinical trials are successful in getting market approval. There are many factors for this poor clinical success for oncology therapeutics, and one of them is the lack of robust preclinical model driving clinical development. Cancer is a very heterogeneous disease and many of the present preclinical models do not represent this heterogeneity. As a result, while a candidate drug may appear good in present preclinical models, they often fail to make the cut in clinical development. To circumvent this critical problem, we have developed a robust TE (Tumor Ecosystem) platform technology using patient tumors, autologous ligands, and immune compartments from the same patients.Our TE platform preserves patient tumor heterogeneity along with other functional and genomic markers and immunogenic cytokines. Efficacy of drugs exposed to the patient's tumor tissue in our TE platform is assessed by as many as 17 orthogonal assays within a week. The results from these assays are converted into a single predictive score called the “M-Score,” and it has been clinically validated using FDA approved drugs in > 1,800 patients across multiple solid and hematological cancers. Our data shows that TE platform predicts treatment outcome of FDA approved drugs in clinical setting with very high sensitivity and specificity. We have the opportunity to use this platform technology to identify cancer indications and appropriate combinations for MIT-1102, a novel HDACi that exhibited potent histone deacetylase inhibitory activity. Our data further indicates that the anti-tumor efficacy of MIT-1102 is superior to Vorinostat and comparable with Pracinostat (SB-939) while being more tolerable than Pracinostat. Results indicated the superiority of MIT-1102 when combined with SOCs in a subset of patients with gastric and pancreatic cancers. We are also using different omics to identify markers associated with response in those tumor types. MIT-1102 has the potential to be more effective in a defined patient population than other molecules in this class. In summary, we have identified a novel, potent HDACi with drug-like properties, and identified the correct cancer indications and most effective combinations using TE platform Technology. Citation Format: Mallikarjun Sundaram, Baraneedharan Ulaganathan, Muthu Dhandapani, Allen Thayakumar, Pragnashree Mukhopadhyay, Saravanan Thiyagarajan, Biswanath Majumder, Prasad Shivarudriah, H Jagadheshan, Ganesh Sambasivam, Steve Birnbuam, Padhma Radhakrishnan, Pradip K. Majumder. Application of patient tumors-derived tumor ecosystem platform for the development of novel HDAC inhibitor in solid cancers. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3736. doi:10.1158/1538-7445.AM2014-3736

Identification and characterization of the spiruchostatin biosynthetic gene cluster enable yield improvement by overexpressing a transcriptional activator

Spiruchostatins A and B are members of the FK228-family of natural products with potent histone deacetylase inhibitory activities and antineoplastic activities. However, their production in the wild-type strain of Pseudomonas sp. Q71576 is low. To improve the yield, the spiruchostatin biosynthetic gene cluster (spi) was first identified by rapid genome sequencing and characterized by genetic mutations. This spi gene cluster encodes a hybrid biosynthetic pathway similar to that encoded by the FK228 biosynthetic gene cluster (dep) in Chromobacterium violaceum No. 968. Each gene cluster contains a pathway regulatory gene (spiR vs. depR), but these two genes encode transcriptional activators of different classes. Overexpression of native spiR or heterologous depR in the wild-type strain of Pseudomonas sp. Q71576 resulted in 268 or 1,285% increase of the combined titer of spiruchostatins A and B, respectively. RT-PCR analysis indicates that overexpression of heterologous depR upregulates the expression of native spiR.

Abstract 2051: PAT-1102, a novel HDAC inhibitor exhibits potent anti-tumor efficacy in patient-derived refractory solid tumors.

Abstract Histone deacetylases (HDAC) have been shown to be involved in oncogenic transformation by mediating transcription factors. Although a few HDAC inhibitors (HDACi) have been shown to be effective in patients with rare leukemia, there is a need to develop best in class HDACi with higher therapeutic index in solid cancers. PAT-1102 is a novel HDACi that exhibited potent histone deacetylase inhibitory activity and growth inhibitory activity against a panel of cell lines in in vitro and in vivo models. Studies indicated that PAT-1102 mediates target modulation (histone hyperacetylation), p21 up regulation, angiogenesis inhibition, and induction of cell cycle arrest in these models. PAT-1102 possesses drug like properties including good aqueous solubility, oral absorption, metabolic stability and favorable pharmacokinetic profile in rodents. It did not show any hERG inhibitory activity, CYP liability and was well tolerated in tumor bearing mice. It had showed a dose dependent tumor growth inhibition of up to 72% in cell line based xenograft models of lung and colorectal cancer. Our data further indicated that the anti-tumor efficacy of PAT-1102 was superior to Vorinostat and comparable with Pracinostat (SB-939) while being more tolerable than Pracinostat. Although it has pan histone deacetylase properties, it showed preferential inhibition of HDAC-3 & HDAC-6. PAT-1102 efficacy was further assessed using “Oncoprint®” platform, a clinically relevant preclinical technology that has been demonstrated to have very high correlation to clinical outcome for chemotherapeutics as well as targeted drugs in multiple solid and hematological cancers (with overall sensitivity of 88% and specificity of 90% in N=500+ patients). Using Oncoprint®, PAT-1102’s efficacy was assessed in patient derived solid cancers (Pancreas, Gastric, Esophagus, Head & Neck, and Colorectal). Further we assessed the efficacy of PAT-1102 alone as well as in combination with various Standard-Of-Care drugs (SOCs) and compared the outcome with efficacy derived from the use of SOCs alone. Our study has been powered to include 75-100 patient derived refractory/recurrent tumors in each indication. Current results indicated the superiority of PAT-1102 when combined with SOCs in a subset of patients with solid cancers. Pre-clinical data shows that PAT-1102 has no toxic effect when given alone or in combination with SOC at efficacious doses . PAT-1102 has the potential to be more effective in a defined patient population than other molecules in this class. In summary, we have identified a novel, potent HDACi with drug like properties. Our data suggest PAT-1102 has the potential to be best in class HDACi when combined with SOC in solid cancers. Clinical development of PAT-1102 in solid cancers will be initiated in 2013. Citation Format: Padhma Radhakrishnan, Muthu Dhandapani, Baraneedharan Ulaganathan, Allen Thayakumar, Saravanan Thiyagarajan, Dency Pinto, D R. Vinod, Biswanath Majumder, Prasad Shivarudriaah, H Jagadheshan, Ganesh Sambasivam, Pradip K. Majumder. PAT-1102, a novel HDAC inhibitor exhibits potent anti-tumor efficacy in patient-derived refractory solid tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2051. doi:10.1158/1538-7445.AM2013-2051

Extractive fermentation for enhanced production of thailandepsin A from Burkholderia thailandensis E264 using polyaromatic adsorbent resin Diaion HP-20

Thailandepsin A is natural product of Burkholderia thailandensis E264 with potent histone deacetylase inhibitory activities and promising anticancer activities. The titer of thailandepsin A is very low (less than 10 mg/l) from limited empirical fermentation. To facilitate preclinical evaluations and potentially clinical development of thailandepsin A, systematic optimization and extractive fermentation of thailandepsin A from B. thailandensis E264 culture in flasks were investigated in this pilot study. The main fermentation parameters--28°C, pH 7.0, inoculum ratio 1% (v/v), incubation duration 60 h, medium volume 26%, shaking speed 170 rpm, and chloroform as extracting solvent--were determined by single factor experiments. Polyaromatic adsorbent resin Diaion HP-20, when added at a concentration of 4% (w/v), was most effective to reduce feedback inhibition of thailandepsin A and to significantly increase the titer of target product. Central composite design was used to further optimize the fermentation medium for B. thailandensis E264. The optimized medium contains glucose 17.89 g/l, tryptone 34.98 g/l, potassium phosphate 24.84 g/l, and sodium citrate 0.01 g/l, which resulted in a large increase of the titer of thailandepsin A to 236.7 mg/l. Finally kinetic models based on the modified logistic and Luedeking-Piret equations were developed, delivering a good description of temporal variations of biomass, product, and substrate in the fermentation process, which could be used as references for developing large-scale fermentation.

Thailandepsin a.

Thailandepsin A [systematic name: (E)-(1S,5S,6R,9S,20R)-6-[(2S)-butan-2-yl]-5-hy­droxy-20-[2-(meth­yl­sulfan­yl)eth­yl]-2-oxa-11,12-dithia-7,19,22-triaza­bicyclo­[7.7.6]docosa-15-ene-3,8,18,21-tetra­one], C23H37N3O6S3, is a newly reported [Wang et al. (2011). J. Nat. Prod. doi:10.1021/np200324x] bicyclic depsipeptide that has potent histone deacetyl­ase inhibitory activity and broad-spectrum anti­proliferative activity. The absolute configuration of thailandepsin A has been determined from the anomalous dispersion and the stereochemistry of all chiral C atoms. Intra­molecular N—H⋯O and N—H⋯S hydrogen bonds occur. Inter­molecular N—H⋯O and O—H⋯O hydrogen bonds are observed in the crystal structure.

Thailandepsins: Bacterial Products with Potent Histone Deacetylase Inhibitory Activities and Broad-Spectrum Antiproliferative Activities

Histone deacetylase (HDAC) inhibitors have emerged as a new class of anticancer drugs, with one synthetic compound, SAHA (vorinostat, Zolinza; 1), and one natural product, FK228 (depsipeptide, romidepsin, Istodax; 2), approved by FDA for clinical use. Our studies of FK228 biosynthesis in Chromobacterium violaceum no. 968 led to the identification of a cryptic biosynthetic gene cluster in the genome of Burkholderia thailandensis E264. Genome mining and genetic manipulation of this gene cluster further led to the discovery of two new products, thailandepsin A (6) and thailandepsin B (7). HDAC inhibition assays showed that thailandepsins have selective inhibition profiles different from that of FK228, with comparable inhibitory activities to those of FK228 toward human HDAC1, HDAC2, HDAC3, HDAC6, HDAC7, and HDAC9 but weaker inhibitory activities than FK228 toward HDAC4 and HDAC8, the latter of which could be beneficial. NCI-60 anticancer screening assays showed that thailandepsins possess broad-spectrum antiproliferative activities with GI50 for over 90% of the tested cell lines at low nanomolar concentrations and potent cytotoxic activities toward certain types of cell lines, particularly for those derived from colon, melanoma, ovarian, and renal cancers. Thailandepsins thus represent new naturally produced HDAC inhibitors that are promising for anticancer drug development.

The Novel HDAC Inhibitor UCL67022 Is Highly Potent in Multiple Myeloma and Non-Hodgkin's Lymphoma and Is Enhanced by Bortezomib.

Introduction: Histone deacetylases (HDACs) regulate the acetylation state of nucleosomal histones and represent a novel target in haematological malignancies. Inhibition of HDACs results in the induction of apoptosis in multiple myeloma (MM) and lymphoma (NHL) cells, associated with the down-regulation of signaling pathways involving IL-6 and IGF-1 and the inactivation of BCL-6. We have therefore investigated the activity of a novel hydroxamic acid HDAC inhibitor (UCL67022) in comparsion with SAHA, alone and in combination with the proteasome inhibitor bortezomib.Methods: HDAC activity in partially purified rat liver homogenate and intact CEM cells was determined using a fluorescent HDAC substrate. The human MM cell lines RPMI 8226/S and U266, and the NHL cell lines SUD-4, CRL, DOHH2, DHL-4, 5, 6, 7, GRANTA-519 and JEKO-1 were used to investigate effects on viable cell number using an ATP-dependent bioluminescence method. Activity against primary malignant cells from patients with MM, DLBCL, FL or CLL was also studied. Western blot analysis was used to investigate changes in acetylated histone-H3 and a-tubulin.Results:UCL67022 showed more potent HDAC inhibitory activity in liver extracts and whole CEM cells than SAHA (IC50 0.05 vs 0.39uM in liver and 0.11 vs 0.33uM in CEM cells). UCL67022 was more potent than SAHA in reducing viable cell number in U266 (EC50 0.14 vs 1.8 uM) and RPMI 8226/S (0.05 vs 0.78 uM) cells. Similarly NHL cell lines were 10–20 fold more sensitive to UCL67022, with median EC50 values of 0.05uM (range 0.03–0.10uM) vs 0.81uM, (range 0.68–1.28uM). In 2 primary MM samples UCL67022 showed increased activity with EC50 values of 0.7uM and 0.11uM vs 12.2uM and 1.1uM for SAHA. 3 FL patient samples and 1 CLL sample were 3.7-fold more sensitive to UCL67022 than SAHA (median EC50 4.7uM vs 17.5uM respectively). Western blot analysis showed a 10-fold difference in histone H3 acetylation between the two compounds, with acetylation returning to pre-treatment levels by 24hr with 3uM SAHA but remaining elevated out to 48hr with 0.3uM UCL67022. Increased acetylation of a-tubulin confirmed the inhibition of HDAC6. Combination with bortezomib at 1, 2 and 4nM in MM cells showed increased antiproliferative activity with both SAHA and UCL67022, with synergistic responses observed in the U226 cell line and in 1 primary sample and additive effects in the others.Conclusions: These data demonstrate the activity of the highly potent, novel HDAC inhibitor UCL67022 in MM and NHL cell lines and primary patient cells. Activity was increased in co-exposures with bortezomib possibly due to inhibition of HDAC6 and subsequent aggresome formation, suggesting a therapeutic advantage with the combination.