HDAC specificity and kinase off-targeting by purine-benzohydroxamate anti-hematological tumor agents

A series of hybrid inhibitors, combining pharmacophores of known kinase inhibitors bearing anilino-purines (ruxolitinib, ibrutinib) and benzohydroxamate HDAC inhibitors (nexturastat A), were generated in the present study. The compounds have been synthesized and tested against solid and hematological tumor cell lines. Compounds 4d-f were the most promising in cytotoxicity assays (IC50 ≤ 50 nM) vs. hematological cells and displayed moderate activity in solid tumor models (EC50 = 9.3-21.7 μM). Compound 4d potently inhibited multiple kinase targets of interest for anticancer effects, including JAK2, JAK3, HDAC1, and HDAC6. Molecular dynamics simulations showed that 4d has stable interactions with HDAC and members of the JAK family, with differences in the hinge binding energy conferring selectivity for JAK3 and JAK2 over JAK1. The kinase inhibition profile of compounds 4d-f allows selective cytotoxicity, with minimal effects on non-tumorigenic cells. Moreover, these compounds have favorable pharmacokinetic profiles, with high stability in human liver microsomes (e.g., see t1/2: >120 min for 4f), low intrinsic clearance, and lack of significant inhibition of four major CYP450 isoforms.

1,3-Diphenylureido hydroxamate as a promising scaffold for generation of potent antimalarial histone deacetylase inhibitors

We report a series of 1,3-diphenylureido hydroxamate HDAC inhibitors evaluated against sensitive and drug-resistant P. falciparum strains. Compounds 8a-d show potent antiplasmodial activity, indicating that a phenyl spacer allows improved potency relative to cinnamyl and di-hydrocinnamyl linkers. In vitro, mechanistic studies demonstrated target activity for PfHDAC1 on a recombinant level, which agreed with cell quantification of the acetylated histone levels. Compounds 6c, 7c, and 8c, identified as the most active in phenotypic assays and PfHDAC1 enzymatic inhibition. Compound 8c stands out as a remarkable inhibitor, displaying an impressive 85% inhibition of PfHDAC1, with an IC50 value of 0.74 µM in the phenotypic screening on Pf3D7 and 0.8 µM against multidrug-resistant PfDd2 parasites. Despite its potent inhibition of PfHDAC1, 8c remains the least active on human HDAC1, displaying remarkable selectivity. In silico studies suggest that the phenyl linker has an ideal length in the series for permitting effective interactions of the hydroxamate with PfHDAC1 and that this compound series could bind as well as in HsHDAC1. Taken together, these results highlight the potential of diphenylurea hydroxamates as a privileged scaffold for the generation of potent antimalarial HDAC inhibitors with improved selectivity over human HDACs.

Design of Novel Phosphopantetheine Adenylyltransferase Inhibitors: a Potential New Approach to Tackle Mycobacterium tuberculosis

BACKGROUND

Tuberculosis (TB) has been a challenging disease worldwide, especially for the neglected poor populations. Presently, there are approximately 2 billion people infected with TB worldwide and 10 million people in the world fell ill with active TB, leading to 1.5 million deaths.

INTRODUCTION

The classic treatment is extensive and the drug and multi drug resistance of Mycobacterium tuberculosis has been a threat to the efficacy of the drugs currently used. Therefore, the rational design of new anti TB candidates is urgently needed.

METHODS

With the aim of contributing to face this challenge, 78 compounds have been proposed based on SBDD (Structure Based Drug Design) strategies applied to target the M. tuberculosis phosphopantetheine adenylyltransferase (MtPPAT) enzyme. Ligand Based Drug Design (LBDD) strategies were also used for establishing structure activity relationships (SAR) and for optimizing the structures. MtPPAT is important for the biosynthesis of coenzyme A (CoA) and it has been studied recently toward the discovery of new inhibitors.

RESULTS

After docking simulations and enthalpy calculations, the interaction of selected compounds with MtPPAT was found to be energetically favorable. The most promising compounds were then synthesized and submitted to anti M. tuberculosis and MtPPAT inhibition assays.

CONCLUSION

One of the compounds synthesized (MCP163), showed the highest activity in both of these assays.

Tetrahydroquinoline-Capped Histone Deacetylase 6 Inhibitor SW-101 Ameliorates Pathological Phenotypes in a Charcot-Marie-Tooth Type 2A Mouse Model

Histone deacetylase 6 (HDAC6) is a promising therapeutic target for the treatment of neurodegenerative disorders. SW-100 (1a), a phenylhydroxamate-based HDAC6 inhibitor (HDAC6i) bearing a tetrahydroquinoline (THQ) capping group, is a highly potent and selective HDAC6i that was shown to be effective in mouse models of Fragile X syndrome and Charcot-Marie-Tooth disease type 2A (CMT2A). In this study, we report the discovery of a new THQ-capped HDAC6i, termed SW-101 (1s), that possesses excellent HDAC6 potency and selectivity, together with markedly improved metabolic stability and druglike properties compared to SW-100 (1a). X-ray crystallography data reveal the molecular basis of HDAC6 inhibition by SW-101 (1s). Importantly, we demonstrate that SW-101 (1s) treatment elevates the impaired level of acetylated α-tubulin in the distal sciatic nerve, counteracts progressive motor dysfunction, and ameliorates neuropathic symptoms in a CMT2A mouse model bearing mutant MFN2. Taken together, these results bode well for the further development of SW-101 (1s) as a disease-modifying HDAC6i.

Mercaptoacetamide: A promising zinc-binding group for the discovery of selective histone deacetylase 6 inhibitors

Histone deacetylase 6 (HDAC6) is a zinc-dependent HDAC that mainly modulates the acetylation status of non-histone substrates, such as α-tubulin and heat shock protein 90 (HSP90). The activity of HDAC6 plays a critical role in cell proliferation, protein trafficking and degradation, cell shape, migration, as well as regulation of immunomodulatory factors. For this reason, HDAC6 influences the progress of cancers, neurodegenerative disorders, and autoimmune responses. In the last few years, the discovery of selective HDAC6 inhibitors (HDAC6is) has become an attractive research area as five HDAC6is are being investigated in phase I/II clinical trials. However, the hydroxamic acid functional group still represents the predominant zinc-binding group (ZBG), that often suffers from poor pharmacokinetics and mutagenic potential, thus impairing the application of hydroxamate-based HDAC6is for long-term therapies. On the other hand, mercaptoacetamide (MCA)-based HDAC6is comprise a class of compounds that, in some cases, display nanomolar HDAC6 potency and a thousand-fold selectivity over class I HDAC isozymes. Moreover, MCA-based HDAC6is lack the mutagenicity associated with the hydroxamate function and display pharmacological effects, demonstrating the potential of this particular ZBG to improve upon the drug-like properties of HDAC6is. Herein, we summarize for the first time the structure-activity relationships (SARs) of MCA-based HDAC6is, discuss their HDAC6 selectivity at the molecular level using inhibitor-HDAC co-crystal structures, and further provide our perspective regarding their drug metabolism, pharmacokinetics, and pharmacological properties.

Rational Design of Suprastat: A Novel Selective Histone Deacetylase 6 Inhibitor with the Ability to Potentiate Immunotherapy in Melanoma Models

Selective inhibition of histone deacetylase 6 (HDAC6) is being recognized as a therapeutic approach for cancers. In this study, we designed a new HDAC6 inhibitor, named Suprastat, using in silico simulations. X-ray crystallography and molecular dynamics simulations provide strong evidence to support the notion that the aminomethyl and hydroxyl groups in the capping group of Suprastat establish significant hydrogen bond interactions, either direct or water-mediated, with residues D460, N530, and S531, which play a vital role in regulating the deacetylase function of the enzyme and which are absent in other isoforms. In vitro characterization of Suprastat demonstrates subnanomolar HDAC6 inhibitory potency and a hundred- to a thousand-fold HDAC6 selectivity over the other HDAC isoforms. In vivo studies reveal that a combination of Suprastat and anti-PD1 immunotherapy enhances antitumor immune response, mediated by a decrease of protumoral M2 macrophages and increased infiltration of antitumor CD8+ effector and memory T-cells.

Neotropical Species of Metaphycus (Hymenoptera, Encyrtidae) Parasitoids of Ceroplastes (Hemiptera, Coccidae): New Species, Interaction Records, and a Checklist

Parasitoids of Ceroplastes Gray were surveyed in the State of São Paulo, Brazil. Among the parasitoids reared, seven species of Metaphycus Mercet (Hymenoptera, Encyrtidae) were obtained. Metaphycusanaluciaesp. nov., M. floridensissp. nov., and M. grandissp. nov., are described as new species, and M. ceros Noyes, M. comes Noyes, M. dardanus Noyes, M. opis Noyes are recorded for the first time from Brazil. Ten new host-parasitoid associations are reported: M. analuciaesp. nov. parasitizing C. formicarius Hempel, C. glomeratus Peronti and C. iheringi Cockerel; M. ceros parasitizing C. cirripediformis Comstock; M. comes parasitizing C. formicarius; M. dardanus parasitizing C. glomeratus; M. floridensissp. nov. parasitizing C. floridensis; M. grandissp. nov. parasitizing C. grandis Hempel; and M. opis parasitizing C. glomeratus and C. janeirensis (Gray). A checklist of Metaphycus species associated with Ceroplastes, their distribution and host ranges are summarized and discussed.

Evaluation of Protein Kinase Inhibitors with PLK4 Cross-Over Potential in a Pre-Clinical Model of Cancer

Polo-like kinase 4 (PLK4) is a cell cycle-regulated protein kinase (PK) recruited at the centrosome in dividing cells. Its overexpression triggers centrosome amplification, which is associated with genetic instability and carcinogenesis. In previous work, we established that PLK4 is overexpressed in pediatric embryonal brain tumors (EBT). We also demonstrated that PLK4 inhibition exerted a cytostatic effect in EBT cells. Here, we examined an array of PK inhibitors (CFI-400945, CFI-400437, centrinone, centrinone-B, R-1530, axitinib, KW-2449, and alisertib) for their potential crossover to PLK4 by comparative structural docking and activity inhibition in multiple established embryonal tumor cell lines (MON, BT-12, BT-16, DAOY, D283). Our analyses demonstrated that: (1) CFI-400437 had the greatest impact overall, but similar to CFI-400945, it is not optimal for brain exposure. Also, their phenotypic anti-cancer impact may, in part, be a consequence of the inhibition of Aurora kinases (AURKs). (2) Centrinone and centrinone B are the most selective PLK4 inhibitors but they are the least likely to penetrate the brain. (3) KW-2449, R-1530 and axitinib are the ones predicted to have moderate-to-good brain penetration. In conclusion, a new selective PLK4 inhibitor with favorable physiochemical properties for optimal brain exposure can be beneficial for the treatment of EBT.

Brain Penetrable Histone Deacetylase 6 Inhibitor SW-100 Ameliorates Memory and Learning Impairments in a Mouse Model of Fragile X Syndrome

Disease-modifying therapies are needed for Fragile X Syndrome (FXS), as at present there are no effective treatments or cures. Herein, we report on a tetrahydroquinoline-based selective histone deacetylase 6 (HDAC6) inhibitor SW-100, its pharmacological and ADMET properties, and its ability to improve upon memory performance in a mouse model of FXS, Fmr1^-/- mice. This small molecule demonstrates good brain penetrance, low-nanomolar potency for the inhibition of HDAC6 (IC₅₀ = 2.3 nM), with at least a thousand-fold selectivity over all other class I, II, and IV HDAC isoforms. Moreover, through its inhibition of the α-tubulin deacetylase domain of HDAC6 (CD2), in cells SW-100 upregulates α-tubulin acetylation with no effect on histone acetylation and selectively restores the impaired acetylated α-tubulin levels in the hippocampus of Fmr1^-/- mice. Lastly, SW-100 ameliorates several memory and learning impairments in Fmr1^-/- mice, thus modeling the intellectual deficiencies associated with FXS, and hence providing a strong rationale for pursuing HDAC6-based therapies for the treatment of this rare disease.

Synthesis and Pharmacological Evaluation of Selective Histone Deacetylase 6 Inhibitors in Melanoma Models

Only a handful of therapies offer significant improvement in the overall survival in cases of melanoma, a cancer whose incidence has continued to rise in the past 30 years. In our effort to identify potent and isoform-selective histone deacetylase (HDAC) inhibitors as a therapeutic approach to melanoma, a series of new HDAC6 inhibitors based on the nexturastat A scaffold were prepared. The new analogues 4d, 4e, and 7b bearing added hydrophilic substituents, so as to establish additional hydrogen bonding on the rim of the HDAC6 catalytic pocket, exhibit improved potency against HDAC6 and retain selectivity over HDAC1. Compound 4d exhibits antiproliferative effects on several types of melanoma and lymphoma cells. Further studies indicates that 4d selectively increases acetylated tubulin levels in vitro and elicits an immune response through down-regulating cytokine IL-10. A preliminary in vivo efficacy study indicates that 4d possesses improved capability to inhibit melanoma tumor growth and that this effect is based on the regulation of inflammatory and immune responses.

Synthesis, Molecular Modeling, and Evaluation of Novel Sulfonylhydrazones as Acetylcholinesterase Inhibitors for Alzheimer's Disease

Alzheimer's disease (AD) is the most common type of dementia and related to the degeneration of hippocampal cholinergic neurons, which dramatically affects cognitive ability. Acetylcholinesterase (AChE) inhibitors are employed as drugs for AD therapy. Three series of sulfonylhydrazone compounds were designed, and their ability to inhibit AChE was evaluated. Fifteen compounds were synthesized and twelve of them had IC₅₀ values of 0.64-51.09 μM. The preliminary structure-activity relationships indicated that the methylcatechol moiety and arylsulfonyl substituents generated better compounds than both the benzodioxole and alkylsulfonyl chains. Molecular dynamics studies of compound 6d showed that the interaction with the peripheral binding site of AChE was similar to donepezil, which may explain its low IC₅₀ (0.64 μM). Furthermore, the drug-likeness of 6d suggests that the compound may have appropriate oral absorption and brain penetration. Compound 6d also presented antiradical activity and was not cytotoxic to LL24 cells, suggesting that this compound might be considered safe. Our findings indicate that arylsulfonylhydrazones may be a promising scaffold for the design of new drug candidates for the treatment of AD.

Toward chelerythrine optimization: Analogues designed by molecular simplification exhibit selective growth inhibition in non-small-cell lung cancer cells

A series of novel chelerythrine analogues was designed and synthesized. Antitumor activity was evaluated against A549, NCI-H1299, NCI-H292, and NCI-H460 non-small-cell lung cancer (NSCLC) cell lines in vitro. The selectivity of the most active analogues and chelerythrine was also evaluated, and we compared their cytotoxicity in NSCLC cells and non-tumorigenic cell lines, including human umbilical vein endothelial cells (HUVECs) and LL24 human lung fibroblasts. In silico studies were performed to establish structure-activity relationships between chelerythrine and the analogues. The results showed that analogue compound 3f induced significant dose-dependent G0/G1 cell cycle arrest in A549 and NCI-H1299 cells. Theoretical studies indicated that the molecular arrangement and electron characteristics of compound 3f were closely related to the profile of chelerythrine, supporting its activity. The present study presents a new and simplified chelerythrinoid scaffold with enhanced selectivity against NSCLC tumor cells for further optimization.

Novel capsaicin analogues as potential anticancer agents: synthesis, biological evaluation, and in silico approach

A novel class of benzo[d][1,3]dioxol-5-ylmethyl alkyl/aryl amide and ester analogues of capsaicin were designed, synthesized, and evaluated for their cytotoxic activity against human and murine cancer cell lines (B16F10, SK-MEL-28, NCI-H1299, NCI-H460, SK-BR-3, and MDA-MB-231) and human lung fibroblasts (MRC-5). Three compounds (5f, 6c, and 6e) selectively inhibited the growth of aggressive cancer cells in the micromolar (µM) range. Furthermore, an exploratory data analysis pointed at the topological and electronic molecular properties as responsible for the discrimination process regarding the set of investigated compounds. The findings suggest that the applied designing strategy, besides providing more potent analogues, indicates the aryl amides and esters as well as the alkyl esters as interesting scaffolds to design and develop novel anticancer agents.

N-[(1,3-Benzodioxol-5-yl)meth-yl]benzene-sulfonamide: an analogue of capsaicin

The title compound, C₁₄H₁₃NO₄S, an analogue of capsaicin, differs from the latter by having a 1,3-benzodioxole ring rather than a 2-meth­oxy­phenol moiety, and having a benzene­sulfonamide group instead of an aliphatic amide chain. The five-membered ring is in an envelope conformation with the methyl­ene C atom lying 0.221 (6) Å out of the plane formed by the other four atoms. The dihedral angle between the phenyl ring and the mean plane of the 1,3-benzodioxole fused-ring system is 84.65 (4)°. In the crystal, mol­ecules aggregate into supra­molecular layers in the ac plane through C—H⋯O, N—H⋯O and C—H⋯π inter­actions.

N-[(1,3-Benzodioxol-5-yl)meth-yl]-4-methyl-benzamide: an analogue of capsaicin

In the title compound, C₁₆H₁₅NO₃, the five-membered 1,3-dioxole ring is in an envelope conformation with the methyl­ene C atom as the flap atom [lying 0.202 (3) Å out of the plane formed by the other four atoms]. The benzene ring makes a dihedral angle of 84.65 (4)° with the best least-squares plane through the 1,3-benzodioxole fused-ring system, which substitutes the 2-methoxyphenol moiety in capsaicin. In the crystal, mol­ecules are connected into a zigzag supra­molecular chain along the c-axis direction by N—H⋯O hydrogen bonds. These chains are connected into a layer in the ac plane by C—H⋯π inter­actions.

Brachymeria pandora (Crawford) (Hymenoptera: Chalcididae) as a new parasitoid of Thyrinteina leucocerae (Rindge) (Lepidoptera: Geometridae) in Brazil

This is the first report of Brachymeria pandora (Crawford) (Hymenoptera: Chalcididae)-parasitizing pupae of the eucalyptus defoliator Thyrinteina leucocerae (Rindge) (Lepidoptera: Geometridae) in Brazil.

Parasitoidism of Chalcidid wasps (Hymenoptera, Chalcididae) on Philornis sp. (Diptera, Muscidae)

Philornis Meinert larvae are known as parasites of birds, with coprophagous, semi-hematophagous or hematophagous habits. Biological data of the larvae of the fifty described species are still scarcely known. Here we describe some aspects of the parasitism of a species of Philornis on Thalurania glaucopis Gmelin (Trochilidae) and record two species of Chalcididae (Hymenoptera) parasitoids, Conura annulifera (Walker, 1864) and Brachymeria podagrica (Fabricius, 1787), reared from Philornis puparia.

Parasitoids of the family Chalcididae colleted in pastures and forests using yellow traps, in Itumbiara, Goiás, Brazil

The objective of this study was to appraise the occurrence of parasitoids of the family Chalcididae in Itumbiara County, State of Goiás, central Brazil. Insect samples were collected in pastures and native forest areas using pan traps, from January to December 1998. The traps consisted of circular yellow plastic containers (30 cm in diameter and 12 cm in height) containing a mixture of 2 L of water, 2 ml of detergent, and 2 ml of formaldehyde. Samplings were performed weekly by placing 10 traps at soil level (5 traps in the pasture and 5 in the woods). During 1998, 121 specimens of Chalcididae were collected. Haltichella sp.4 was the most abundant species collected (15.7%).