Publications by authors named "Wolfgang Sippl"

200 Publications

The potential for histone deacetylase (HDAC) inhibitors as cestocidal drugs.

PLoS Negl Trop Dis 2021 Mar 3;15(3):e0009226. Epub 2021 Mar 3.

Instituto de Investigaciones en Microbiología y Parasitología Médica (IMPaM), Facultad de Medicina, Universidad de Buenos Aires (UBA), Ciudad Autónoma de Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.

Background: Echinococcosis and cysticercosis are neglected tropical diseases caused by cestode parasites (family Taeniidae). Not only there is a small number of approved anthelmintics for the treatment of these cestodiases, but also some of them are not highly effective against larval stages, such that identifying novel drug targets and their associated compounds is critical. Histone deacetylase (HDAC) enzymes are validated drug targets in cancers and other diseases, and have been gaining relevance for developing new potential anti-parasitic treatments in the last years. Here, we present the anthelmintic profile for a panel of recently developed HDAC inhibitors against the model cestode Mesocestoides vogae (syn. M. corti).

Methodology/principal Findings: Phenotypic screening was performed on M. vogae by motility measurements and optical microscopic observations. Some HDAC inhibitors showed potent anthelmintic activities; three of them-entinostat, TH65, and TH92 -had pronounced anthelmintic effects, reducing parasite viability by ~100% at concentrations of ≤ 20 μM. These compounds were selected for further characterization and showed anthelmintic effects in the micromolar range and in a time- and dose-dependent manner. Moreover, these compounds induced major alterations on the morphology and ultrastructural features of M. vogae. The potencies of these compounds were higher than albendazole and the anthelmintic effects were irreversible. Additionally, we evaluated pairwise drug combinations of these HDAC inhibitors and albendazole. The results suggested a positive interaction in the anthelmintic effect for individual pairs of compounds. Due to the maximum dose approved for entinostat, adjustments in the dose regime and/or combinations with currently-used anthelmintic drugs are needed, and the selectivity of TH65 and TH92 towards parasite targets should be assessed.

Conclusion, Significance: The results presented here suggest that HDAC inhibitors represent novel and potent drug candidates against cestodes and pave the way to understanding the roles of HDACs in these parasites.
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http://dx.doi.org/10.1371/journal.pntd.0009226DOI Listing
March 2021

Design, synthesis, and biological evaluation of new urolithin amides as multitarget agents against Alzheimer's disease.

Arch Pharm (Weinheim) 2021 Jan 29:e2000467. Epub 2021 Jan 29.

Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Eastern Mediterranean University, Famagusta, TR North Cyprus, Turkey.

A series of urolithin amide (i.e., URO-4-URO-10 and THU-4-THU-10) derivatives was designed and synthesized, and their chemical structures were confirmed with spectroscopic techniques and elemental analysis. The title compounds and synthesis intermediates (THU-1-THU-10 and URO-1-URO-10) were evaluated for their potential to inhibit acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), and monoamine oxidase B (MAO-B). Compounds THU-4 and THU-8 were found to be the most potent inhibitors for the cholinesterases and MAO-B, respectively. The docking studies were also employed to evaluate the binding modes of the most active compounds with AChE, BuChE, and MAO-B. Furthermore, the moderate-to-strong activities of the compounds were also displayed in amyloid-beta inhibition and antioxidant assay systems. The results pointed out that the urolithin scaffold can be employed in drug design studies for the development of multitarget ligands acting on various cascades shown to be important within the pathophysiology of Alzheimer's disease.
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http://dx.doi.org/10.1002/ardp.202000467DOI Listing
January 2021

Strategies To Design Selective Histone Deacetylase Inhibitors.

ChemMedChem 2021 Jan 11. Epub 2021 Jan 11.

Institute of Pharmacy, Martin Luther University of Halle - Wittenberg, Kurt Mothes Straße 3, 06120, Halle (Saale), Germany.

This review classifies drug-design strategies successfully implemented in the development of histone deacetylase (HDAC) inhibitors, which have many applications including cancer treatment. Our focus is on especially demanded selective HDAC inhibitors and their structure-activity relationships in relation to corresponding protein structures. The main part of the paper is divided into six subsections each narrating how optimization of one of six structural features can influence inhibitor selectivity. It starts with the impact of the zinc binding group on selectivity, continues with the optimization of the linker placed in the substrate binding tunnel as well as the adjustment of the cap group interacting with the surface of the protein, and ends with the addition of groups targeting class-specific sub-pockets: the side-pocket-, lower-pocket- and foot-pocket-targeting groups. The review is rounded off with a conclusion and an outlook on the future of HDAC inhibitor design.
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http://dx.doi.org/10.1002/cmdc.202000934DOI Listing
January 2021

Editorial to Special Issue-"Structure-Activity Relationships (SAR) of Natural Products".

Molecules 2021 Jan 6;26(2). Epub 2021 Jan 6.

Institute of Pharmacy, Martin-Luther University of Halle-Wittenberg, Kurt-Mothes-Str. 3, 06122 Halle, Germany.

The topic of structure-activity-relationships (SAR) has recently drawn a lot of attention, and there is increasing interest in natural products (NPs) as a "source of inspiration" for the discovery of new lead compounds [...].
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http://dx.doi.org/10.3390/molecules26020250DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7825126PMC
January 2021

Alkaloids with Anti-Onchocercal Activity from Stapf (Apocynaceae): Identification and Molecular Modeling.

Molecules 2020 Dec 25;26(1). Epub 2020 Dec 25.

Department of Chemistry, Faculty of Science, University of Buea, P.O. Box 63, Buea CM-00237, Cameroon.

A new iboga-vobasine-type isomeric bisindole alkaloid named voacamine A (), along with eight known compounds-voacangine (), voacristine (), coronaridine (), tabernanthine (), iboxygaine (), voacamine (), voacorine () and conoduramine ()-were isolated from the stem bark of . The structures of the compounds were determined by comprehensive spectroscopic analyses. Compounds , , , , , and were found to inhibit the motility of both the microfilariae (Mf) and adult male worms of , in a dose-dependent manner, but were only moderately active on the adult female worms upon biochemical assessment at 30 μM drug concentrations. The IC values of the isolates are 2.49-5.49 µM for microfilariae and 3.45-17.87 µM for adult males. Homology modeling was used to generate a 3D model of the thioredoxin reductase target and docking simulation, followed by molecular dynamics and binding free energy calculations attempted to offer an explanation of the anti-onchocercal structure-activity relationship (SAR) of the isolated compounds. These alkaloids are new potential leads for the development of antifilarial drugs. The results of this study validate the traditional use of in the treatment of human onchocerciasis.
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http://dx.doi.org/10.3390/molecules26010070DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7795662PMC
December 2020

How to Separate Kinase Inhibition from Undesired Monoamine Oxidase A Inhibition-The Development of the DYRK1A Inhibitor AnnH75 from the Alkaloid Harmine.

Molecules 2020 Dec 16;25(24). Epub 2020 Dec 16.

Department of Pharmacy-Center for Drug Research, Ludwig-Maximilians University, 81377 Munich, Germany.

The β-carboline alkaloid harmine is a potent DYRK1A inhibitor, but suffers from undesired potent inhibition of MAO-A, which strongly limits its application. We synthesized more than 60 analogues of harmine, either by direct modification of the alkaloid or by de novo synthesis of β-carboline and related scaffolds aimed at learning about structure-activity relationships for inhibition of both DYRK1A and MAO-A, with the ultimate goal of separating desired DYRK1A inhibition from undesired MAO-A inhibition. Based on evidence from published crystal structures of harmine bound to each of these enzymes, we performed systematic structure modifications of harmine yielding DYRK1A-selective inhibitors characterized by small polar substituents at N-9 (which preserve DYRK1A inhibition and eliminate MAO-A inhibition) and beneficial residues at C-1 (methyl or chlorine). The top compound remains a potent DYRK1A inhibitor, and it is devoid of MAO-A inhibition. Its binding mode to DYRK1A was elucidated by crystal structure analysis, and docking experiments provided additional insights for this attractive series of DYRK1A and MAO-A inhibitors.
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http://dx.doi.org/10.3390/molecules25245962DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7765920PMC
December 2020

Pharmacoinformatic Investigation of Medicinal Plants from East Africa.

Mol Inform 2020 11 8;39(11):e2000163. Epub 2020 Oct 8.

Institute of Pharmacy, Martin-Luther University of Halle-Wittenberg, Kurt-Mothes-Str. 3, 06120, Halle/Saale, Germany.

Medicinal plants have widely been used in the traditional treatment of ailments and have been proven effective. Their contribution still holds an important place in modern drug discovery due to their chemical, and biological diversities. However, the poor documentation of traditional medicine, in developing African countries for instance, can lead to the loss of knowledge related to such practices. In this study, we present the Eastern Africa Natural Products Database (EANPDB) containing the structural and bioactivity information of 1870 unique molecules isolated from about 300 source species from the Eastern African region. This represents the largest collection of natural products (NPs) from this geographical region, covering literature data of the period from 1962 to 2019. The computed physicochemical properties and toxicity profiles of each compound have been included. A comparative analysis of some physico-chemical properties like molecular weight, H-bond donor/acceptor, logP , etc. as well scaffold diversity analysis has been carried out with other published NP databases. EANPDB was combined with the previously published Northern African Natural Products Database (NANPDB), to form a merger African Natural Products Database (ANPDB), containing ∼6500 unique molecules isolated from about 1000 source species (freely available at http://african-compounds.org). As a case study, latrunculins A and B isolated from the sponge Negombata magnifica (Podospongiidae) with previously reported antitumour activities, were identified via substructure searching as molecules to be explored as putative binders of histone deacetylases (HDACs).
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http://dx.doi.org/10.1002/minf.202000163DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7685152PMC
November 2020

Identification of the subtype-selective Sirt5 inhibitor balsalazide through systematic SAR analysis and rationalization via theoretical investigations.

Eur J Med Chem 2020 Nov 1;206:112676. Epub 2020 Aug 1.

Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians University, Butenandtstraße 5-13, 81377, Munich, Germany. Electronic address:

We report here an extensive structure-activity relationship study of balsalazide, which was previously identified in a high-throughput screening as an inhibitor of Sirt5. To get a closer understanding why this compound is able to inhibit Sirt5, we initially performed docking experiments comparing the binding mode of a succinylated peptide as the natural substrate and balsalazide with Sirt5 in the presence of NAD. Based on the evidence gathered here, we designed and synthesized 13 analogues of balsalazide, in which single functional groups were either deleted or slightly altered to investigate which of them are mandatory for high inhibitory activity. Our study confirms that balsalazide with all its given functional groups is an inhibitor of Sirt5 in the low micromolar concentration range and structural modifications presented in this study did not increase potency. While changes on the N-aroyl-β-alanine side chain eliminated potency, the introduction of a truncated salicylic acid part minimally altered potency. Calculations of the associated reaction paths showed that the inhibition potency is very likely dominated by the stability of the inhibitor-enzyme complex and not the type of inhibition (covalent vs. non-covalent). Further in-vitro characterization in a trypsin coupled assay determined that the tested inhibitors showed no competition towards NAD or the synthetic substrate analogue ZKsA. In addition, investigations for subtype selectivity revealed that balsalazide is a subtype-selective Sirt5 inhibitor, and our initial SAR and docking studies pave the way for further optimization.
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http://dx.doi.org/10.1016/j.ejmech.2020.112676DOI Listing
November 2020

Histone deacetylases inhibitors as new potential drugs against Leishmania braziliensis, the main causative agent of new world tegumentary leishmaniasis.

Biochem Pharmacol 2020 10 7;180:114191. Epub 2020 Aug 7.

Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Viçosa, Minas Gerais, Brazil; Consortium A-ParaDDisE- Anti- Parasite Drug Discovery in Epigenetics - http://a-paraddise.cebio.org. Electronic address:

The protozoan parasite Leishmania braziliensis is a major causative agent of the neglected tropical diseases Cutaneous and Mucocutaneous Leishmaniases in the New World. There are no vaccines to prevent the infection and the treatment relies on few drugs that often display high toxicity and costs. Thus, chemotherapeutic alternatives are required. Histone Deacetylases (HDACs) are epigenetic enzymes involved in the control of chromatin structure. In this work, we tested an in-house library of 78 hydroxamic acid derivatives as putative inhibitors of L. braziliensis HDACs (HDACi). The compounds were evaluated in relation to the toxicity to the host cell macrophage and to the leishmanicidal effect against L. braziliensis during in vitro infection. Eight HDACi showed significant leishmanicidal effects and the top 5 compounds showed effective concentrations (EC) in the range of 4.38 to 10.21 μM and selectivity indexes (SI) from of 6 to 21.7. Analyses by Transmission Electron Microscopy (TEM) indicated induction of apoptotic cell death of L. braziliensis amastigotes with a necrotic phenotype. An altered chromatin condensation pattern and cellular disorganization of intracellular amastigotes was also observed. A tight connection between the mitochondrion and nuclear protrusions, presumably of endoplasmic reticulum origin, was found in parasites but not in the host cell. In flow cytometry (FC) analyses, HDACi promoted parasite cell cycle arrest in the G2-M phase and no changes were found in macrophages. In addition, the direct effect of HDACi against the promastigotes showed apoptosis as the main mechanism of cell death. The FC results corroborate the TEM analyses indicating that the HDACi lead to changes in the cell cycle and induction of apoptosis of L. braziliensis. The production of nitric oxide by the infected macrophages was not altered after treatment with the top 5 compounds. Taken together, our results evidenced new HDACi as promising agents for the development of new treatments for American Tegumentary Leishmaniasis caused by L. braziliensis.
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http://dx.doi.org/10.1016/j.bcp.2020.114191DOI Listing
October 2020

Natural Products as Modulators of Sirtuins.

Molecules 2020 Jul 20;25(14). Epub 2020 Jul 20.

Institute of Pharmacy, Martin-Luther University of Halle-Wittenberg, Kurt-Mothes-Str. 3, 06120 Halle (Saale), Germany.

Natural products have been used for the treatment of human diseases since ancient history. Over time, due to the lack of precise tools and techniques for the separation, purification, and structural elucidation of active constituents in natural resources there has been a decline in financial support and efforts in characterization of natural products. Advances in the design of chemical compounds and the understanding of their functions is of pharmacological importance for the biomedical field. However, natural products regained attention as sources of novel drug candidates upon recent developments and progress in technology. Natural compounds were shown to bear an inherent ability to bind to biomacromolecules and cover an unparalleled chemical space in comparison to most libraries used for high-throughput screening. Thus, natural products hold a great potential for the drug discovery of new scaffolds for therapeutic targets such as sirtuins. Sirtuins are Class III histone deacetylases that have been linked to many diseases such as Parkinson`s disease, Alzheimer's disease, type II diabetes, and cancer linked to aging. In this review, we examine the revitalization of interest in natural products for drug discovery and discuss natural product modulators of sirtuins that could serve as a starting point for the development of isoform selective and highly potent drug-like compounds, as well as the potential application of naturally occurring sirtuin inhibitors in human health and those in clinical trials.
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http://dx.doi.org/10.3390/molecules25143287DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7397027PMC
July 2020

HaloTag-Targeted Sirtuin-Rearranging Ligand (SirReal) for the Development of Proteolysis-Targeting Chimeras (PROTACs) against the Lysine Deacetylase Sirtuin 2 (Sirt2)*.

Chembiochem 2020 Dec 27;21(23):3371-3376. Epub 2020 Aug 27.

Institute of Pharmaceutical Sciences, University of Freiburg, Albertstraße 25, 79104, Freiburg im Breisgau, Germany.

We have discovered the sirtuin-rearranging ligands (SirReals) as a novel class of highly potent and selective inhibitors of the NAD -dependent lysine deacetylase sirtuin 2 (Sirt2). In previous studies, conjugation of a SirReal with a ligand for the E3 ubiquitin ligase cereblon to form a so-called proteolysis-targeting chimera (PROTAC) enabled small-molecule-induced degradation of Sirt2. Herein, we report the structure-based development of a chloroalkylated SirReal that induces the degradation of Sirt2 mediated by Halo-tagged E3 ubiquitin ligases. Using this orthogonal approach for Sirt2 degradation, we show that other E3 ligases than cereblon, such as the E3 ubiquitin ligase parkin, can also be harnessed for small-molecule-induced Sirt2 degradation, thereby emphasizing the great potential of parkin to be used as an E3 ligase for new PROTACs approaches. Thus, our study provides new insights into targeted protein degradation in general and Sirt2 degradation in particular.
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http://dx.doi.org/10.1002/cbic.202000351DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7754454PMC
December 2020

Novel Histone Deacetylase Inhibitors and HIV-1 Latency-Reversing Agents Identified by Large-Scale Virtual Screening.

Front Pharmacol 2020 17;11:905. Epub 2020 Jun 17.

Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada.

Current antiretroviral therapies used for HIV management do not target latent viral reservoirs in humans. The experimental "shock-and-kill" therapeutic approach involves use of latency-reversal agents (LRAs) that reactivate HIV expression in reservoir-containing cells, followed by infected cell elimination through viral or host immune cytopathic effects. Several LRAs that function as histone deacetylase (HDAC) inhibitors are reported to reverse HIV latency in cells and in clinical trials; however, none to date have consistently reduced viral reservoirs in humans, prompting a need to identify new LRAs. Toward this goal, we describe here a virtual screening (VS) approach which uses 14 reported HDAC inhibitors to probe PubChem and identifies 60 LRA candidates. We then show that four screening "hits" including (S)--Hydroxy-4-(3-methyl-2-phenylbutanamido)benzamide (compound ), -(4-Aminophenyl)heptanamide (), -[4-(Heptanoylamino)phenyl]heptanamide (), and 4-(1,3-Dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)--(2-hydroxyethyl)butanamide () inhibit HDAC activity and/or reverse HIV latency . This study demonstrates and supports that VS-based approaches can readily identify novel HDAC inhibitors and LRAs, which in turn may help toward inhibitor design and chemical optimization efforts for improved HIV shock-and-kill-based efforts.
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http://dx.doi.org/10.3389/fphar.2020.00905DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7311767PMC
June 2020

Pharmacological inhibition of lysine-specific demethylase 1 (LSD1) induces global transcriptional deregulation and ultrastructural alterations that impair viability in Schistosoma mansoni.

PLoS Negl Trop Dis 2020 07 1;14(7):e0008332. Epub 2020 Jul 1.

Instituto de Bioquímica Médica Leopoldo de Meis, Programa de Biologia Molecular e Biotecnologia, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.

Treatment and control of schistosomiasis still rely on only one effective drug, praziquantel (PZQ) and, due to mass treatment, the increasing risk of selecting for schistosome strains that are resistant to PZQ has alerted investigators to the urgent need to develop novel therapeutic strategies. The histone-modifying enzymes (HMEs) represent promising targets for the development of epigenetic drugs against Schistosoma mansoni. In the present study, we targeted the S. mansoni lysine-specific demethylase 1 (SmLSD1), a transcriptional corepressor, using a novel and selective synthetic inhibitor, MC3935, which was used to treat schistosomula and adult worms in vitro. By using cell viability assays and optical and electron microscopy, we showed that treatment with MC3935 affected parasite motility, egg-laying, tegument, and cellular organelle structures, culminating in the death of schistosomula and adult worms. In silico molecular modeling and docking analysis suggested that MC3935 binds to the catalytic pocket of SmLSD1. Western blot analysis revealed that MC3935 inhibited SmLSD1 demethylation activity of H3K4me1/2. Knockdown of SmLSD1 by RNAi recapitulated MC3935 phenotypes in adult worms. RNA-Seq analysis of MC3935-treated parasites revealed significant differences in gene expression related to critical biological processes. Collectively, our findings show that SmLSD1 is a promising drug target for the treatment of schistosomiasis and strongly support the further development and in vivo testing of selective schistosome LSD1 inhibitors.
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http://dx.doi.org/10.1371/journal.pntd.0008332DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7329083PMC
July 2020

Design, synthesis, and biological evaluation of dual targeting inhibitors of histone deacetylase 6/8 and bromodomain BRPF1.

Eur J Med Chem 2020 Aug 18;200:112338. Epub 2020 May 18.

Institute of Pharmacy, Martin-Luther University of Halle-Wittenberg, 06120, Halle/Saale, Germany. Electronic address:

Histone modifying proteins, specifically histone deacetylases (HDACs) and bromodomains, have emerged as novel promising targets for anticancer therapy. In the current work, based on available crystal structures and docking studies, we designed dual inhibitors of both HDAC6/8 and the bromodomain and PHD finger containing protein 1 (BRPF1). Biochemical and biophysical tests showed that compounds 23a,b and 37 are nanomolar inhibitors of both target proteins. Detailed structure-activity relationships were deduced for the synthesized inhibitors which were supported by extensive docking and molecular dynamics studies. Cellular testing in acute myeloid leukemia (AML) cells showed only a weak effect, most probably because of the poor permeability of the inhibitors. We also aimed to analyse the target engagement and the cellular activity of the novel inhibitors by determining the protein acetylation levels in cells by western blotting (tubulin vs histone acetylation), and by assessing their effects on various cancer cell lines.
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http://dx.doi.org/10.1016/j.ejmech.2020.112338DOI Listing
August 2020

Synthesis, Characterization, Molecular Docking, and Biological Activities of Some Natural and Synthetic Urolithin Analogs.

Chem Biodivers 2020 Aug 20;17(8):e2000197. Epub 2020 Jul 20.

Faculty of Pharmacy, Department of Pharmaceutical Chemistry, Eastern Mediterranean University, via Mersin 10, TR-99628, Famagusta, North Cyprus, Turkey.

Urolithins (that is, hydroxy substituted benzo[c]chromen-6-one derivatives) are formed within the gastrointestinal tract following to the exposure to various ellagitannin rich diet, particularly involving pomegranate, nuts, and berries. Regarding the bioavailability deficiency of ellagitannins, the biological activities obtained through the extracts of these dietaries are attributed to the urolithin compounds, since they are bioavailable. Particularly, there are studies indicating the importance of ellagitannin-rich food for protective and alternative treatment of Alzheimer's Disease (AD). From this perspective, within this study, the major urolithins (that is, urolithins A and B), their methyl ether metabolites, as well as some synthetic urolithin analogs have been synthesized and screened for their biological activities in various enzyme inhibition (acetylcholinesterase, butyrylcholinesterase, monoamine oxidase B, cyclooxygenase 1, and cyclooxygenase 2) and antioxidant (DPPH radical scavenging) assay systems. The results pointed out the potential of urolithins to act as inhibitors on these receptors. Docking studies were also performed to investigate the possible interactions.
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http://dx.doi.org/10.1002/cbdv.202000197DOI Listing
August 2020

Sirtuin 1 Inhibiting Thiocyanates (S1th)-A New Class of Isotype Selective Inhibitors of NAD Dependent Lysine Deacetylases.

Front Oncol 2020 30;10:657. Epub 2020 Apr 30.

Department of Pharmaceutical and Medicinal Chemistry, Institute of Pharmaceutical Sciences, University of Freiburg, Freiburg im Breisgau, Germany.

Sirtuin 1 (Sirt1) is a NAD dependent lysine deacetylase associated with the pathogenesis of various diseases including cancer. In many cancer types Sirt1 expression is increased and higher levels have been associated with metastasis and poor prognosis. However, it was also shown, that Sirt1 can have tumor suppressing properties and in some instances even a dual role for the same cancer type has been reported. Increased Sirt1 activity has been linked to extension of the life span of cells, respectively, organisms by promoting DNA repair processes and downregulation of tumor suppressor proteins. This may have the downside of enhancing tumor growth and metastasis. In mice embryonic fibroblasts depletion of Sirt1 was shown to decrease levels of the DNA damage sensor histone H2AX. Impairment of DNA repair mechanisms by Sirt1 can promote tumorigenesis but also lower chemoresistance toward DNA targeting therapies. Despite many biological studies, there is currently just one small molecule Sirt1 inhibitor in clinical trials. Selisistat (EX-527) reached phase III clinical trials for treatment of Huntington's Disease. New small molecule Sirt1 modulators are crucial for further investigation of the contradicting roles of Sirt1 in cancer. We tested a small library of commercially available compounds that were proposed by virtual screening and docking studies against Sirt1, 2 and 3. A thienopyrimidone featuring a phenyl thiocyanate moiety was found to selectively inhibit Sirt1 with an IC of 13 μM. Structural analogs lacking the thiocyanate function did not show inhibition of Sirt1 revealing this group as key for the selectivity and affinity toward Sirt1. Further analogs with higher solubility were identified through iterative docking studies and testing. The most active compounds (down to 5 μM IC) were further studied in cells. The ratio of phosphorylated γH2AX to unmodified H2AX is lower when Sirt1 is depleted or inhibited. Our new Sirtuin 1 inhibiting thiocyanates (S1th) lead to similarly lowered γH2AX/H2AX ratios in mouse embryonic fibroblasts as Sirt1 knockout and treatment with the reference inhibitor EX-527. In addition to that we were able to show antiproliferative activity, inhibition of migration and colony forming as well as hyperacetylation of Sirt1 targets p53 and H3 by the S1th in cervical cancer cells (HeLa). These results reveal thiocyanates as a promising new class of selective Sirt1 inhibitors.
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http://dx.doi.org/10.3389/fonc.2020.00657DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7203344PMC
April 2020

The potential of anti-malarial compounds derived from African medicinal plants: a review of pharmacological evaluations from 2013 to 2019.

Malar J 2020 May 18;19(1):183. Epub 2020 May 18.

Department of Physics, Ecole Normale Supérieure, University of Yaoundé I, P. O. Box 47, Yaoundé, Cameroon.

Background: African Traditional Medicine (ATM) is used for the healthcare of about 80% of the rural populations of the continent of Africa. The practices of ATM make use of plant-products, which are known to contain plant-based secondary metabolites or natural products (NPs), likely to play key roles in drug discovery, particularly as lead compounds. For various reasons, including resistance of strains of Plasmodium to known anti-malarial drugs, local African populations often resort to plant-based treatments and/or a combination of this and standard anti-malarial regimens. Emphasis has been laid in this review to present the anti-malarial virtue of the most recently published phytochemicals or natural products, which have been tested by in vitro and in vivo assays.

Methods: The data was based on the current version of the African Compound Libraries, which are constantly being updated based on inputs from journal articles and student theses (M.Sc/Ph.D) from African University libraries. Emphasis was laid on data published after 2012. In order to carry out the original data collection, currently being included in the African Compounds Database, individual journal websites were queried using the country names in Africa as search terms. Over 40,000 articles "hits" were originally retrieved, then reduced to about 9000 articles. The retained articles/theses was further queried with the search terms "malaria", "malarial", "plasmodium", "plasmodial" and a combination of them, resulting in over 500 articles. Those including compounds with anti-malarial activities for which the measured activities fell within the established cut off values numbered 55, which were all cited in the review as relevant references.

Results And Discussion: Pure compounds derived from African medicinal plants with demonstrated anti-malarial/antiplasmodial properties with activities ranging from "very active" to "weakly active" have been discussed. The majority of the 187 natural products were terpenoids (30%), followed by flavonoids (22%), alkaloids (19%) and quinones (15%), with each of the other compound classes being less than 5% of the entire compound collection. It was also observed that most of the plant species from which the compounds were identified were of the families Rubiaceae, Meliaceae and Asphodelaceae. The review is intended to continue laying the groundwork for an African-based anti-malarial drug discovery project.
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http://dx.doi.org/10.1186/s12936-020-03231-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7236213PMC
May 2020

Synthesis and biological evaluation of triazolyl-substituted benzyloxyacetohydroxamic acids as LpxC inhibitors.

Bioorg Med Chem 2020 07 25;28(13):115529. Epub 2020 Apr 25.

Institute of Organic Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany; German Center for Infection Research (DZIF), Partner Site Hamburg-Lübeck-Borstel-Riems. Electronic address:

The bacterial deacetylase LpxC is a promising target for the development of antibiotics selectively combating Gram-negative bacteria. To improve the biological activity of the reported benzyloxyacetohydroxamic acid 9 ((S)-N-hydroxy-2-{2-hydroxy-1-[4-(phenylethynyl)phenyl]ethoxy}acetamide), its hydroxy group was replaced by a triazole ring. Therefore, in divergent syntheses, triazole derivatives exhibiting rigid and flexible lipophilic side chains, different configurations at their stereocenter, and various substitution patterns at the triazole ring were synthesized, tested for antibacterial and LpxC inhibitory activity, and structure-activity relationships were deduced based on docking and binding energy calculations.
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http://dx.doi.org/10.1016/j.bmc.2020.115529DOI Listing
July 2020

Proteolysis targeting chimeras (PROTACs) for epigenetics research.

Curr Opin Chem Biol 2020 08 5;57:8-16. Epub 2020 Mar 5.

Institute of Pharmaceutical Sciences, University of Freiburg, Albertstraße 25, Freiburg, 79104, Germany; CIBSS - Centre for Integrative Biological Signalling Studies, University of Freiburg, Schänzlestraße 18, Freiburg, 79104, Germany. Electronic address:

Proteolysis targeting chimeras (PROTACs) are heterobifunctional molecules and allow selective protein degradation by addressing the natural ubiquitin proteasome system. As this new strategy of chemically induced protein degradation can serve as a biological tool and provides new possibilities for drug discovery, it has been applied to a variety of targets including (nuclear) receptors, kinases, and epigenetic proteins. A lot of PROTACs have already been designed in the field of epigenetics, and their synthesis and characterization highly contributed to structural optimization and improved mechanistic understanding of these molecules. In this review, we will discuss and summarize recent advances in PROTAC discovery with focus on epigenetic targets.
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http://dx.doi.org/10.1016/j.cbpa.2020.01.010DOI Listing
August 2020

Negative allosteric modulators of the GluN2B NMDA receptor with phenylethylamine structure embedded in ring-expanded and ring-contracted scaffolds.

Eur J Med Chem 2020 Mar 10;190:112138. Epub 2020 Feb 10.

Institut für Pharmazeutische und Medizinische Chemie der Universität Münster, Corrensstraße 48, D-48149, Münster, Germany; Cells-in-Motion Cluster of Excellence (EXC 1003 - CiM), Westfälische Wilhelms-Universität, Münster, Germany. Electronic address:

A set of GluN2B NMDA receptor antagonists with conformationally restricted phenylethylamine substructure was prepared and pharmacologically evaluated. The phenylethylamine substructure was embedded in ring expanded 3-benzazocines 4 as well as ring-contracted tetralinamines 6 and indanamines 7. The ligands 4, 6 and 7 were synthesized by reductive alkylation of secondary amine 11, reductive amination of ketones 12 and 16 and nucleophilic substitution of nosylates 14 and 17. The moderate GluN2B affinity of 3-benzazocine 4d (K = 32 nM) translated into moderate cytoprotective activity (IC = 890 nM) and moderate ion channel inhibition (60% at 10 μM) in two-electrode voltage clamp experiments with GluN1a/GluN2B expressing oocytes. Although some of the tetralinamines 6 and indanamines 7 showed very high GluN2B affinity (e.g. K (7f) = 3.2 nM), they could not inhibit glutamate/glycine inducted cytotoxicity. The low cytoprotective activity of 3-benzazocines 4, tetralinamines 6 and indanamines 7 was attributed to the missing OH moiety at the benzene ring and/or in benzylic position. Docking studies showed that the novel GluN2B ligands adopt similar binding poses as Ro 25-6981 with the central H-bond interaction between the protonated amino moiety of the ligands and the carbamoyl moiety of Gln110. However, due to the lack of a second H-bond forming group, the ligands can adopt two binding poses within the ifenprodil binding pocket.
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http://dx.doi.org/10.1016/j.ejmech.2020.112138DOI Listing
March 2020

Structure-Based Design, Synthesis, and Biological Evaluation of Triazole-Based smHDAC8 Inhibitors.

ChemMedChem 2020 04 9;15(7):571-584. Epub 2020 Jan 9.

Department of Chemistry Institute of Organic Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146, Hamburg, Germany.

Schistosomiasis is a neglected tropical disease caused by parasitic flatworms of the genus Schistosoma, which affects over 200 million people worldwide and leads to at least 300,000 deaths every year. In this study, initial screening revealed the triazole-based hydroxamate 2 b (N-hydroxy-1-phenyl-1H-1,2,3-triazole-4-carboxamide) exhibiting potent inhibitory activity toward the novel antiparasitic target Schistosoma mansoni histone deacetylase 8 (smHDAC8) and promising selectivity over the major human HDACs. Subsequent crystallographic studies of the 2 b/smHDAC8 complex revealed key interactions between the inhibitor and the enzyme's active site, thus explaining the unique selectivity profile of the inhibitor. Further chemical modifications of 2 b led to the discovery of 4-fluorophenoxy derivative 21 (1-[5-chloro-2-(4-fluorophenoxy)phenyl]-N-hydroxy-1H-1,2,3-triazole-4-carboxamide), a nanomolar smHDAC8 inhibitor (IC =0.5 μM), exceeding the smHDAC8 inhibitory activity of 2 b and SAHA (vorinostat), while exhibiting an improved selectivity profile over the investigated human HDACs. Collectively, this study reveals specific interactions between smHDAC8 and the synthesized triazole-based inhibitors and demonstrates that these small molecules represent promising lead structures, which could be further developed in the search for novel drugs for the treatment of schistosomiasis.
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http://dx.doi.org/10.1002/cmdc.201900583DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7187165PMC
April 2020

Continuous Activity Assay for HDAC11 Enabling Reevaluation of HDAC Inhibitors.

ACS Omega 2019 Nov 15;4(22):19895-19904. Epub 2019 Nov 15.

Department of Enzymology, Institute of Biochemistry and Biotechnology, Charles Tanford Protein Centre, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, 06120 Halle (Saale), Germany.

Histone deacetylase 11 (HDAC11) preferentially removes fatty acid residues from lysine side chains in a peptide or protein environment. Here, we report the development and validation of a continuous fluorescence-based activity assay using an internally quenched TNFα-derived peptide derivative as a substrate. The threonine residue in the +1 position was replaced by the quencher amino acid 3'-nitro-l-tyrosine and the fatty acyl moiety substituted by 2-aminobenzoylated 11-aminoundecanoic acid. The resulting peptide substrate enables fluorescence-based direct and continuous readout of HDAC11-mediated amide bond cleavage fully compatible with high-throughput screening formats. The '-factor is higher than 0.85 for the 15 μM substrate concentration, and the signal-to-noise ratio exceeds 150 for 384-well plates. In the absence of NAD, this substrate is specific for HDAC11. Reevaluation of inhibitory data using our novel assay revealed limited potency and selectivity of known HDAC inhibitors, including Elevenostat, a putative HDAC11-specific inhibitor.
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http://dx.doi.org/10.1021/acsomega.9b02808DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6882135PMC
November 2019

One-Atom Substitution Enables Direct and Continuous Monitoring of Histone Deacylase Activity.

Biochemistry 2019 12 14;58(48):4777-4789. Epub 2019 Nov 14.

Department of Enzymology, Institute of Biochemistry and Biotechnology, Charles-Tanford-Protein Center , Martin-Luther-University Halle-Wittenberg , 06120 Halle/Saale , Germany.

We developed a one-step direct assay for the determination of histone deacylase (HDAC) activity by substituting the carbonyl oxygen of the acyl moiety with sulfur, resulting in thioacylated lysine side chains. This modification is recognized by class I HDACs with different efficiencies ranging from not accepted for HDAC1 to kinetic constants similar to that of the parent oxo substrate for HDAC8. Class II HDACs can hydrolyze thioacylated substrates with approximately 5-10-fold reduced values, which resembles the effect of thioamide substitution in metallo-protease substrates. Class IV HDAC11 accepts thiomyristoyl modification less efficiently with an ∼5-fold reduced specificity constant. On the basis of the unique spectroscopic properties of thioamide bonds (strong absorption in spectral range of 260-280 nm and efficient fluorescence quenching), HDAC-mediated cleavage of thioamides could be followed by ultraviolet-visible and fluorescence spectroscopy in a continuous manner. The HDAC activity assay is compatible with microtiter plate-based screening formats up to 1536-well plates with ' factors of >0.75 and signal-to-noise ratios of >50. Using thioacylated lysine residues in p53-derived peptides, we optimized substrates for HDAC8 with a catalytic efficiency of >250000 M s, which are more than 100-fold more effective than most of the known substrates. We determined inhibition constants of several inhibitors for human HDACs using thioacylated peptidic substrates and found good correlation with the values from the literature. On the other hand, we could introduce N-methylated, N-acylated lysine residues as inhibitors for HDACs with an IC value of 1 μM for an N-methylated, N-myristoylated peptide derivative and human HDAC11.
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http://dx.doi.org/10.1021/acs.biochem.9b00786DOI Listing
December 2019

Impact of hydroxy moieties at the benzo[7]annulene ring system of GluN2B ligands: Design, synthesis and biological evaluation.

Bioorg Med Chem 2019 12 8;27(23):115146. Epub 2019 Oct 8.

Institut für Pharmazeutische und Medizinische Chemie der Universität Münster, Corrensstraße 48, 48149 Münster, Germany; Cells-in-Motion Cluster of Excellence (EXC 1003 - CiM), Westfälische Wilhelms-Universität Münster, Germany. Electronic address:

In this study, the impact of one or two hydroxy moieties at the benzo[7]annulene scaffold on the GluN2B affinity and cytoprotective activity was analyzed. The key intermediate for the synthesis of OH-substituted benzo[7]annulenamines 11-13 and 17 was the epoxyketone 8. Reductive epoxide opening of 8 resulted with high regioselectivity in the 5-hydroxyketone 9 (Pd(OAc), HCOH, phosphane ligand) or the 6-hydroxyketone 10 (H, Pd/C), whereas hydrolysis in aqueous dioxane led to the dihydroxyketone 14. Reductive amination of these ketones with primary amines and NaBH(OAc) afforded the benzo[7]annulenamines 11-13 and 17. In receptor binding studies 5-OH derivatives 11 and 12 showed higher GluN2B affinity than 6-OH derivatives 13, which in turn were more active than 5,6-di-OH derivative 17a. The same order was found for the cytoprotective activity of the ligands. The tertiary amine 12a with one OH moiety in 5-position represents the most promising GluN2B negative allosteric modulator with a binding affinity of K = 49 nM and a cytoprotective activity of IC = 580 nM. In the binding pocket 12a shows a crucial H-bond between the benzylic OH moiety and the backbone carbonyl O-atom of Ser132 (GluN1b). It was concluded that a 5-OH moiety is essential for the inhibition of the NMDA receptor associated ion channel, whereas a OH moiety in 6-position is detrimental for binding and inhibition. An OH or CHOH moiety at 2-position results in binding at the ifenprodil binding site, but very weak ion channel inhibition.
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http://dx.doi.org/10.1016/j.bmc.2019.115146DOI Listing
December 2019

The Clinically Used Iron Chelator Deferasirox Is an Inhibitor of Epigenetic JumonjiC Domain-Containing Histone Demethylases.

ACS Chem Biol 2019 08 19;14(8):1737-1750. Epub 2019 Jul 19.

Institute of Pharmaceutical Sciences , Albert-Ludwigs-Universität Freiburg , Albertstraße 25 , 79104 Freiburg i.Br. , Germany.

Fe(II)- and 2-oxoglutarate (2OG)-dependent JumonjiC domain-containing histone demethylases (JmjC KDMs) are "epigenetic eraser" enzymes involved in the regulation of gene expression and are emerging drug targets in oncology. We screened a set of clinically used iron chelators and report that they potently inhibit JMJD2A (KDM4A) . Mode of action investigations revealed that one compound, deferasirox, is a active site-binding inhibitor as shown by kinetic and spectroscopic studies. Synthesis of derivatives with improved cell permeability resulted in significant upregulation of histone trimethylation and potent cancer cell growth inhibition. Deferasirox was also found to inhibit human 2OG-dependent hypoxia inducible factor prolyl hydroxylase activity. Therapeutic effects of clinically used deferasirox may thus involve transcriptional regulation through 2OG oxygenase inhibition. Deferasirox might provide a useful starting point for the development of novel anticancer drugs targeting 2OG oxygenases and a valuable tool compound for investigations of KDM function.
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http://dx.doi.org/10.1021/acschembio.9b00289DOI Listing
August 2019

MMP-14 degrades tropoelastin and elastin.

Biochimie 2019 Oct 3;165:32-39. Epub 2019 Jul 3.

Institute of Pharmacy, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany; Department of Pharmacy, LEO Foundation Center for Cutaneous Drug Delivery, University of Copenhagen, Copenhagen, Denmark. Electronic address:

Matrix metalloproteinases are a class of enzymes, which degrade extracellular matrix components such as collagens, elastin, laminin or fibronectin. So far, four matrix metalloproteinases have been shown to degrade elastin and its precursor tropoelastin, namely matrix metalloproteinase-2, -7, -9 and -12. This study focuses on investigating the elastinolytic capability of membrane-type 1 matrix metalloproteinase, also known as matrix metalloproteinase-14. We digested recombinant human tropoelastin and human skin elastin with matrix metalloproteinase-14 and analyzed the peptide mixtures using complementary mass spectrometric techniques and bioinformatics tools. The results and additional molecular docking studies show that matrix metalloproteinase-14 cleaves tropoelastin as well as elastin. While tropoelastin was well degraded, fewer cleavages occurred in the highly cross-linked mature elastin. The study also provides insights into the cleavage preferences of the enzyme. Similar to cleavage preferences of matrix metalloproteinases-2, -7, -9 and -12, matrix metalloproteinase-14 prefers small and medium-sized hydrophobic residues including Gly, Ala, Leu and Val at cleavage site P1'. Pro, Gly and Ala were preferably found at P1-P4 and P2'-P4' in both tropoelastin and elastin. Cleavage of mature skin elastin by matrix metalloproteinase-14 released a variety of bioactive elastin peptides, which indicates that the enzyme may play a role in the development and progression of cardiovascular diseases that go along with elastin breakdown.
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http://dx.doi.org/10.1016/j.biochi.2019.07.001DOI Listing
October 2019

Proline-based hydroxamates targeting the zinc-dependent deacetylase LpxC: Synthesis, antibacterial properties, and docking studies.

Bioorg Med Chem 2019 05 30;27(10):1997-2018. Epub 2019 Mar 30.

Institute of Organic Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany; German Center for Infection Research (DZIF), Partner Site Hamburg-Lübeck-Borstel-Riems, Germany. Electronic address:

The Zn-dependent deacetylase LpxC is an essential enzyme in Gram-negative bacteria, which has been validated as antibacterial drug target. Herein we report the chiral-pool synthesis of novel d- and l-proline-derived 3,4-dihydroxypyrrolidine hydroxamates and compare their antibacterial and LpxC inhibitory activities with the ones of 4-monosubstituted and 3,4-unsubstituted proline derivatives. With potent antibacterial activities against several Gram-negative pathogens, the l-proline-based tertiary amine 41g ((S)-N-hydroxy-1-(4-{[4-(morpholinomethyl)phenyl]ethynyl}benzyl)pyrrolidine-2-carboxamide) was found to be the most active antibacterial compound within the investigated series, also showing some selectivity toward EcLpxC (K = 1.4 μM) over several human MMPs.
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http://dx.doi.org/10.1016/j.bmc.2019.03.056DOI Listing
May 2019

Chiral Pool Synthesis, Biological Evaluation and Molecular Docking Studies of C-Furanosidic LpxC Inhibitors.

ChemMedChem 2019 04 12;14(8):871-886. Epub 2019 Mar 12.

Department of Chemistry, Institute of Organic Chemistry, University of Hamburg, Martin-Luther-King Platz 6, 20146, Hamburg, Germany.

Inhibitors of the bacterial deacetylase LpxC are a promising class of novel antibiotics, being selectively active against Gram-negative bacteria. To improve the biological activity of reported C-furanosidic LpxC inhibitors, the stereochemistry at positions 3 and 4 of the tetrahydrofuran ring was varied. In chiral pool syntheses starting from d-gulono-γ-lactone and d-ribose, a series of (3S,4R)-configured dihydroxytetrahydrofuran derivatives was obtained, of which the (2S,5S)-configured hydroxamic acid 15 ((2S,3S,4R,5S)-N,3,4-trihydroxy-5-(4-{[4-(morpholinomethyl)phenyl]ethynyl}phenyl)tetrahydrofuran-2-carboxamide) was found to be the most potent LpxC inhibitor (K =0.4 μm), exhibiting the highest antibacterial activity against E. coli BL21 (DE3) and the D22 strain. Additionally, molecular docking studies were performed to rationalize the obtained structure-activity relationships.
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http://dx.doi.org/10.1002/cmdc.201900068DOI Listing
April 2019

Preclinical Evaluation of Benzazepine-Based PET Radioligands ()- and ()-C-Me-NB1 Reveals Distinct Enantiomeric Binding Patterns and a Tightrope Walk Between GluN2B- and σ-Receptor-Targeted PET Imaging.

J Nucl Med 2019 08 25;60(8):1167-1173. Epub 2019 Jan 25.

Institute of Pharmaceutical Sciences, ETH Zurich, Zurich, Switzerland

The study aims to investigate the performance characteristics of the enantiomers of C-Me-NB1, a recently reported PET imaging probe that targets the GluN2B subunit of -methyl-d-aspartate (NMDA) receptors. Reference compound Me-NB1 (inhibition constant for hGluN1/GluN2B, 5.4 nM) and the phenolic precursor were prepared via multistep synthesis. Following chiral resolution by high-performance liquid chromatography, enantiopure precursor compounds, ()NB1 and ()NB1, were labeled with C and validated in rodents using in vitro/ex vivo autoradiography, PET experiments, and dose-response studies. To illustrate the translational relevance, ()C-Me-NB1 was validated in autoradiographic studies using postmortem human GluN2B-rich cortical and GluN2B-deficient cerebellar brain slices. To determine target engagement, receptor occupancy was assessed at different plasma concentrations of CP101,606, a GluN2B receptor antagonist. The radiosynthesis of () and ()C-Me-NB1 was accomplished in 42% ± 9% (decay-corrected) radiochemical yields. Molar activity ranged from 40 to 336 GBq/μmol, and an excellent radiochemical purity of greater than 99% was achieved. Although ()C-Me-NB1 displayed heterogeneous accumulation with high selectivity for the GluN2B-rich forebrain, ()C-Me-NB1 revealed a homogeneous distribution across all brain regions in rodent brain autoradiograms and predominantly exhibited σ-receptor binding. Similar to rodent brain, ()C-Me-NB1 showed in postmortem human brain tissues higher binding in the cortex than in the cerebellum. Coincubation of the GluN2B-antagonist CERC-301 (1 μM) reduced cortical but not cerebellar binding, demonstrating the specificity of ()C-Me-NB1 binding to the human GluN2B-containing NMDA receptor. In vivo specificity of ()C-Me-NB1 in the GluN2B-expressing cortex, striatum, thalamus, and hippocampus was demonstrated by PET imaging in rodents. Applying GluN2B-antagonist eliprodil, an evident dose-response behavior was observed with ()C-Me-NB1 but not with ()C-Me-NB1. Our findings further underline the tightrope walk between GluN2B- and σ-receptor-targeted imaging, illustrated by the entirely different receptor binding behavior of the 2 radioligand enantiomers. ()C-Me-NB1 is a highly selective and specific PET radioligand for imaging the GluN2B subunit of the NMDA receptor. The entirely different receptor binding behavior of ()C-Me-NB1 and ()C-Me-NB1 raises awareness of a delicate balance that is underlying the selective targeting of either GluN2B-carrying NMDA or σ-receptors.
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http://dx.doi.org/10.2967/jnumed.118.221051DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6681693PMC
August 2019

Synthesis and Biological Investigation of Phenothiazine-Based Benzhydroxamic Acids as Selective Histone Deacetylase 6 Inhibitors.

J Med Chem 2019 02 1;62(3):1138-1166. Epub 2019 Feb 1.

Department of Pharmacy-Center for Drug Research , Ludwig-Maximilians University Munich , Butenandtstr. 5-13 , 81377 Munich , Germany.

The phenothiazine system was identified as a favorable cap group for potent and selective histone deacetylase 6 (HDAC6) inhibitors. Here, we report the preparation and systematic variation of phenothiazines and their analogues containing a benzhydroxamic acid moiety as the zinc-binding group. We evaluated their ability to selectively inhibit HDAC6 by a recombinant HDAC enzyme assay, by determining the protein acetylation levels in cells by western blotting (tubulin vs histone acetylation), and by assessing their effects on various cancer cell lines. Structure-activity relationship studies revealed that incorporation of a nitrogen atom into the phenothiazine framework results in increased potency and selectivity for HDAC6 (more than 500-fold selectivity relative to the inhibition of HDAC1, HDAC4, and HDAC8), as rationalized by molecular modeling and docking studies. The binding mode was confirmed by co-crystallization of the potent azaphenothiazine inhibitor with catalytic domain 2 from Danio rerio HDAC6.
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http://dx.doi.org/10.1021/acs.jmedchem.8b01090DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6519732PMC
February 2019