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Bernauer T, Nitsche V, Kaiser J, Gertzen CGW, Höfner G, Niessen KV, Seeger T, Steinritz D, Worek F, Gohlke H, Wanner KT, Paintner FF. Synthesis and Biological Evaluation of Novel MB327 Analogs as Resensitizers for Desensitized Nicotinic Acetylcholine Receptors after Intoxication with Nerve Agents. Toxicol Lett 2024:S0378-4274(24)00103-6. [PMID: 38759939 DOI: 10.1016/j.toxlet.2024.05.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 05/06/2024] [Accepted: 05/14/2024] [Indexed: 05/19/2024]
Abstract
Poisoning with organophosphorus compounds, which can lead to a cholinergic crisis due to the inhibition of acetylcholinesterase and the subsequent accumulation of acetylcholine (ACh) in the synaptic cleft, is a serious problem for which treatment options are currently insufficient. Our approach to broadening the therapeutic spectrum is to use agents that interact directly with desensitized nicotinic acetylcholine receptors (nAChRs) in order to induce functional recovery after ACh overstimulation. Although MB327, one of the most prominent compounds investigated in this context, has already shown positive properties in terms of muscle force recovery, this compound is not suitable for use as a therapeutic agent due to its insufficient potency. By means of in silico studies based on our recently presented allosteric binding pocket at the nAChR, i.e. the MB327-PAM-1 binding site, three promising MB327 analogs with a 4-aminopyridinium ion partial structure (PTM0056, PTM0062 and PTM0063) were identified. In this study, we present the synthesis and biological evaluation of a series of new analogs of the aforementioned compounds with a 4-aminopyridinium ion partial structure (PTM0064-PTM0072), as well as hydroxy-substituted analogs of MB327 (PTMD90-0012 and PTMD90-0015) designed to substitute entropically unfavorable water clusters identified during molecular dynamics simulations. The compounds were characterized in terms of their binding affinity towards the aforementioned binding site by applying the UNC0642 MS Binding Assays and in terms of their muscle force reactivation in rat diaphragm myography. More potent compounds were identified compared to MB327, as some of them showed a higher affinity towards MB327-PAM-1 and also a higher recovery of neuromuscular transmission at lower compound concentrations. To improve the treatment of organophosphate poisoning, direct targeting of nAChRs with appropriate compounds is a key step, and this study is an important contribution to this research.
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Affiliation(s)
- Tamara Bernauer
- Department of Pharmacy - Center for Drug Research Ludwig-Maximilians-Universität München Butenandtstraße 5-13, 81377 Munich Germany
| | - Valentin Nitsche
- Department of Pharmacy - Center for Drug Research Ludwig-Maximilians-Universität München Butenandtstraße 5-13, 81377 Munich Germany
| | - Jesko Kaiser
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf Germany
| | - Christoph G W Gertzen
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf Germany
| | - Georg Höfner
- Department of Pharmacy - Center for Drug Research Ludwig-Maximilians-Universität München Butenandtstraße 5-13, 81377 Munich Germany
| | - Karin V Niessen
- Bundeswehr Institute of Pharmacology and Toxicology, Neuherbergstraße 11, 80937 Munich Germany
| | - Thomas Seeger
- Bundeswehr Institute of Pharmacology and Toxicology, Neuherbergstraße 11, 80937 Munich Germany
| | - Dirk Steinritz
- Bundeswehr Institute of Pharmacology and Toxicology, Neuherbergstraße 11, 80937 Munich Germany
| | - Franz Worek
- Bundeswehr Institute of Pharmacology and Toxicology, Neuherbergstraße 11, 80937 Munich Germany
| | - Holger Gohlke
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf Germany; John von Neumann Institute for Computing (NIC), Jülich Supercomputing Centre (JSC), Institute of Biological Information Processing (IBI-7: Structural Biochemistry) & Institute of Bio- and Geosciences (IBG-4: Bioinformatics) Forschungszentrum Jülich, Wilhelm-Johnen-Straße, 52428 Jülich Germany
| | - Klaus T Wanner
- Department of Pharmacy - Center for Drug Research Ludwig-Maximilians-Universität München Butenandtstraße 5-13, 81377 Munich Germany
| | - Franz F Paintner
- Department of Pharmacy - Center for Drug Research Ludwig-Maximilians-Universität München Butenandtstraße 5-13, 81377 Munich Germany.
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Sichler S, Höfner G, Nitsche V, Niessen KV, Seeger T, Worek F, Paintner FF, Wanner KT. Screening for new ligands of the MB327-PAM-1 binding site of the nicotinic acetylcholine receptor. Toxicol Lett 2024; 394:23-31. [PMID: 38387764 DOI: 10.1016/j.toxlet.2024.02.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 01/08/2024] [Accepted: 02/18/2024] [Indexed: 02/24/2024]
Abstract
Intoxications with organophosphorus compounds (OPCs) effect a severe impairment of cholinergic neurotransmission that, as a result of overstimulation may lead to desensitization of nicotinic acetylcholine receptors (nAChRs) and finally to death due to respiratory paralysis. So far, therapeutics, that are capable to address and revert desensitized neuromuscular nAChRs into their resting, i.e. functional state are still missing. Still, among a class of compounds termed bispyridinium salts, which are characterized by the presence of two pyridinium subunits, constituents have been identified, that can counteract organophosphate poisoning by resensitizing desensitized nAChRs. According to comprehensive modeling studies this effect is mediated by an allosteric binding site at the nAChR termed MB327-PAM-1 site. For MB327, the most prominent representative of the bispyridinium salts and all other analogues studied so far, the affinity for the aforementioned binding site and the intrinsic activity measured in ex vivo and in in vivo experiments are distinctly too low, to meet the criteria to be fulfilled for therapeutic use. Hence, in order to identify new compounds with higher affinities for the MB327-PAM-1 binding site, as a basic requirement for an enhanced potency, two compound libraries, the ChemDiv library with 60 constituents and the Tocriscreen Plus library with 1280 members have been screened for hit compounds addressing the MB327-PAM-1 binding site, utilizing the [2H6]MB327 MS Binding Assay recently developed by us. This led to the identification of a set of 10 chemically diverse compounds, all of which exhibit an IC50 value of ≤ 10 µM (in the [2H6]MB327 MS Binding Assay), which had been defined as selection criteria. The three most affine ligands, which besides a quinazoline scaffold share similarities with regard to the substitution pattern and the nature of the substituents, are UNC0638, UNC0642 and UNC0646. With binding affinities expressed as pKi values of 6.01 ± 0.10, 5.97 ± 0.05 and 6.23 ± 0.02, respectively, these compounds exceed the binding affinity of MB327 by more than one log unit. This renders them promising starting points for the development of drugs for the treatment of organophosphorus poisoning by addressing the MB327-PAM-1 binding site of the nAChR.
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Affiliation(s)
- Sonja Sichler
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Georg Höfner
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Valentin Nitsche
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Karin V Niessen
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany
| | - Thomas Seeger
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany
| | - Franz Worek
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany
| | - Franz F Paintner
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Klaus T Wanner
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
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Amend N, Timperley CM, Bird M, Green AC, Worek F, Seeger T. Restoration of nerve agent impaired neuromuscular transmission in rat diaphragm by bispyridinium non-oximes - Structure-activity relationships. Toxicology 2024; 503:153741. [PMID: 38311098 DOI: 10.1016/j.tox.2024.153741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Revised: 01/29/2024] [Accepted: 02/01/2024] [Indexed: 02/06/2024]
Abstract
Organophosphate (OP) poisoning is currently treated with atropine, oximes and benzodiazepines. The nicotinic signs, i.e., respiratory impairment, can only be targeted indirectly via the use of oximes as reactivators of OP-inhibited acetylcholinesterase. Hence, compounds selectively targeting nicotinic acetylcholine receptors (nAChRs) might fundamentally improve current treatment options. The bispyridinium compound MB327 has previously shown some therapeutic effect against nerve agents in vitro and in vivo. Nevertheless, compound optimization was deemed necessary, due to limitations (e.g., toxicity and efficacy). The current study investigated a series of 4-tert-butyl bispyridinium compounds and of corresponding bispyridinium compounds without substituents in a rat diaphragm model using an indirect field stimulation technique. The length of the respective linker influenced the ability of the bispyridinium compounds to restore muscle function in rat hemidiaphragms. The current data show structure-activity relationships for a series of bispyridinium compounds and provide insight for future structure-based molecular modeling.
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Affiliation(s)
- Niko Amend
- Bundeswehr Institute of Pharmacology and Toxicology, Neuherbergstrasse 11, 80937 Munich, Germany; Walther-Straub-Institute of Pharmacology and Toxicology, Faculty of Medicine, Ludwig-Maximilians-Universität München, Goethestr. 33, 80336 Munich, Germany.
| | - Christopher M Timperley
- Chemical, Biological and Radiological (CBR) Division, Defence Science and Technology Laboratory (Dstl), Porton Down, Salisbury, Wiltshire SP4 0JQ, UK
| | - Mike Bird
- Chemical, Biological and Radiological (CBR) Division, Defence Science and Technology Laboratory (Dstl), Porton Down, Salisbury, Wiltshire SP4 0JQ, UK
| | - A Christopher Green
- Chemical, Biological and Radiological (CBR) Division, Defence Science and Technology Laboratory (Dstl), Porton Down, Salisbury, Wiltshire SP4 0JQ, UK
| | - Franz Worek
- Bundeswehr Institute of Pharmacology and Toxicology, Neuherbergstrasse 11, 80937 Munich, Germany
| | - Thomas Seeger
- Bundeswehr Institute of Pharmacology and Toxicology, Neuherbergstrasse 11, 80937 Munich, Germany
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Nitsche V, Höfner G, Kaiser J, Gertzen CGW, Seeger T, Niessen KV, Steinritz D, Worek F, Gohlke H, Paintner FF, Wanner KT. MS Binding Assays with UNC0642 as reporter ligand for the MB327 binding site of the nicotinic acetylcholine receptor. Toxicol Lett 2024; 392:94-106. [PMID: 38216073 DOI: 10.1016/j.toxlet.2024.01.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Revised: 12/28/2023] [Accepted: 01/06/2024] [Indexed: 01/14/2024]
Abstract
Intoxications with organophosphorus compounds (OPCs) based chemical warfare agents and insecticides may result in a detrimental overstimulation of muscarinic and nicotinic acetylcholine receptors evolving into a cholinergic crisis leading to death due to respiratory failure. In the case of the nicotinic acetylcholine receptor (nAChR), overstimulation leads to a desensitization of the receptor, which cannot be pharmacologically treated so far. Still, compounds interacting with the MB327 binding site of the nAChR like the bispyridinium salt MB327 have been found to re-establish the functional activity of the desensitized receptor. Only recently, a series of quinazoline derivatives with UNC0642 as one of the most prominent representatives has been identified to address the MB327 binding site of the nAChR, as well. In this study, UNC0642 has been utilized as a reporter ligand to establish new Binding Assays for this target. These assays follow the concept of MS Binding Assays for which by assessing the amount of bound reporter ligand by mass spectrometry no radiolabeled material is required. According to the results of the performed MS Binding Assays comprising saturation and competition experiments it can be concluded, that UNC0642 used as a reporter ligand addresses the MB327 binding site of the Torpedo-nAChR. This is further supported by the outcome of ex vivo studies carried out with poisoned rat diaphragm muscles as well as by in silico studies predicting the binding mode of UNC0646, an analog of UNC0642 with the highest binding affinity, in the recently proposed binding site of MB327 (MB327-PAM-1). With UNC0642 addressing the MB327 binding site of the Torpedo-nAChR, this and related quinazoline derivatives represent a promising starting point for the development of novel ligands of the nAChR as antidotes for the treatment of intoxications with organophosphorus compounds. Further, the new MS Binding Assays are a potent alternative to established assays and of particular value, as they do not require the use of radiolabeled material and are based on a commercially available compound as reporter ligand, UNC0642, exhibiting one of the highest binding affinities for the MB327 binding site known so far.
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Affiliation(s)
- Valentin Nitsche
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Georg Höfner
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Jesko Kaiser
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine Universität Düsseldorf, Düsseldorf, Germany
| | - Christoph G W Gertzen
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine Universität Düsseldorf, Düsseldorf, Germany
| | - Thomas Seeger
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany
| | - Karin V Niessen
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany
| | - Dirk Steinritz
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany
| | - Franz Worek
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany
| | - Holger Gohlke
- Institute for Pharmaceutical and Medicinal Chemistry, Heinrich Heine Universität Düsseldorf, Düsseldorf, Germany; Institute of Bio, and Geosciences (IBG-4: Bioinformatics), Forschungszentrum Jülich, Jülich, Germany
| | - Franz F Paintner
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Klaus T Wanner
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany.
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Kaiser J, Gertzen CG, Bernauer T, Höfner G, Niessen KV, Seeger T, Paintner FF, Wanner KT, Worek F, Thiermann H, Gohlke H. A novel binding site in the nicotinic acetylcholine receptor for MB327 can explain its allosteric modulation relevant for organophosphorus-poisoning treatment. Toxicol Lett 2022; 373:160-171. [DOI: 10.1016/j.toxlet.2022.11.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 11/25/2022] [Indexed: 11/27/2022]
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Kassa J, Timperley CM, Bird M, Green AC, Tattersall JEH. Influence of Experimental End Point on the Therapeutic Efficacy of Essential and Additional Antidotes in Organophosphorus Nerve Agent-Intoxicated Mice. Toxics 2022; 10:192. [PMID: 35448453 DOI: 10.3390/toxics10040192] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 04/12/2022] [Accepted: 04/13/2022] [Indexed: 02/04/2023]
Abstract
The therapeutic efficacy of treatments for acute intoxication with highly toxic organophosphorus compounds, called nerve agents, usually involves determination of LD50 values 24 h after nerve agent challenge without and with a single administration of the treatment. Herein, the LD50 values of four nerve agents (sarin, soman, tabun and cyclosarin) for non-treated and treated intoxication were investigated in mice for experimental end points of 6 and 24 h. The LD50 values of the nerve agents were evaluated by probit-logarithmical analysis of deaths within 6 and 24 h of i.m. challenge of the nerve agent at five different doses, using six mice per dose. The efficiency of atropine alone or atropine in combination with an oxime was practically the same at 6 and 24 h. The therapeutic efficacy of the higher dose of the antinicotinic compound MB327 was slightly higher at the 6 h end point compared to the 24 h end point for soman and tabun intoxication. A higher dose of MB327 increased the therapeutic efficacy of atropine alone for sarin, soman and tabun intoxication, and that of the standard antidotal treatment (atropine and oxime) for sarin and tabun intoxication. The therapeutic efficacy of MB327 was lower than the oxime-based antidotal treatment. To compare the 6 and 24 h end points, the influence of the experimental end point was not observed, with the exception of the higher dose of MB327. In addition, only a negligible beneficial impact of the compound MB327 was observed. Nevertheless, antinicotinics may offer an additional avenue for countering poisoning by nerve agents that are difficult to treat, and synthetic and biological studies towards the development of such novel drugs based on the core bispyridinium structure or other molecular scaffolds should continue.
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Epstein M, Bali K, Piggot TJ, Green AC, Timperley CM, Bird M, Tattersall JEH, Bermudez I, Biggin PC. Molecular determinants of binding of non-oxime bispyridinium nerve agent antidote compounds to the adult muscle nAChR. Toxicol Lett 2021; 340:114-122. [PMID: 33482275 DOI: 10.1016/j.toxlet.2021.01.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 01/11/2021] [Accepted: 01/11/2021] [Indexed: 11/27/2022]
Abstract
Organophosphorus nerve agents (NAs) are the most lethal chemical warfare agents and have been used by state and non-state actors since their discovery in the 1930s. They covalently modify acetylcholinesterase, preventing the breakdown of acetylcholine (ACh) with subsequent loss of synaptic transmission, which can result in death. Despite the availability of several antidotes for OPNA exposure, none directly targets the nicotinic acetylcholine receptor (nAChR) mediated component of toxicity. Non-oxime bispyridinium compounds (BPDs) have been shown previously to partially counteract the effects of NAs at skeletal muscle tissue, and this has been attributed to inhibition of the muscle nAChR. Functional data indicate that, by increasing the length of the alkyl linker between the pyridinium moieties of BPDs, the antagonistic activity at nAChRs can be improved. Molecular dynamics simulations of the adult muscle nAChR in the presence of BPDs identified key residues likely to be involved in binding. Subsequent two-electrode voltage clamp recordings showed that one of the residues, εY131, acts as an allosteric determinant of BPD binding, and that longer BPDs have a greater stabilizing effect on the orthosteric loop C than shorter ones. The work reported will inform future design work on novel antidotes for treating NA exposure.
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Affiliation(s)
- Max Epstein
- Department of Biochemistry, Structural Bioinformatics and Computational Biochemistry, University of Oxford, Oxford, UK
| | - Karan Bali
- Department of Biochemistry, Structural Bioinformatics and Computational Biochemistry, University of Oxford, Oxford, UK; Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge, UK
| | - Thomas J Piggot
- Chemical, Biological and Radiological Sciences Division, Defence Science and Technology Laboratory (DSTL), Porton Down, Salisbury, Wiltshire, UK
| | - A Christopher Green
- Chemical, Biological and Radiological Sciences Division, Defence Science and Technology Laboratory (DSTL), Porton Down, Salisbury, Wiltshire, UK
| | - Christopher M Timperley
- Chemical, Biological and Radiological Sciences Division, Defence Science and Technology Laboratory (DSTL), Porton Down, Salisbury, Wiltshire, UK
| | - Mike Bird
- Chemical, Biological and Radiological Sciences Division, Defence Science and Technology Laboratory (DSTL), Porton Down, Salisbury, Wiltshire, UK
| | - John E H Tattersall
- Chemical, Biological and Radiological Sciences Division, Defence Science and Technology Laboratory (DSTL), Porton Down, Salisbury, Wiltshire, UK
| | - Isabel Bermudez
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford, UK
| | - Philip C Biggin
- Department of Biochemistry, Structural Bioinformatics and Computational Biochemistry, University of Oxford, Oxford, UK.
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Amend N, Niessen KV, Seeger T, Wille T, Worek F, Thiermann H. Diagnostics and treatment of nerve agent poisoning—current status and future developments. Ann N Y Acad Sci 2020; 1479:13-28. [DOI: 10.1111/nyas.14336] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 02/25/2020] [Accepted: 03/05/2020] [Indexed: 12/20/2022]
Affiliation(s)
- Niko Amend
- Bundeswehr Institute of Pharmacology and Toxicology Munich Germany
| | - Karin V. Niessen
- Bundeswehr Institute of Pharmacology and Toxicology Munich Germany
| | - Thomas Seeger
- Bundeswehr Institute of Pharmacology and Toxicology Munich Germany
| | - Timo Wille
- Bundeswehr Institute of Pharmacology and Toxicology Munich Germany
| | - Franz Worek
- Bundeswehr Institute of Pharmacology and Toxicology Munich Germany
| | - Horst Thiermann
- Bundeswehr Institute of Pharmacology and Toxicology Munich Germany
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