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Hong WD, Gibbons PD, Leung SC, Amewu R, Stocks PA, Stachulski A, Horta P, Cristiano MLS, Shone AE, Moss D, Ardrey A, Sharma R, Warman AJ, Bedingfield PTP, Fisher NE, Aljayyoussi G, Mead S, Caws M, Berry NG, Ward SA, Biagini GA, O'Neill PM, Nixon GL. Rational Design, Synthesis, and Biological Evaluation of Heterocyclic Quinolones Targeting the Respiratory Chain of Mycobacterium tuberculosis. J Med Chem 2017; 60:3703-3726. [PMID: 28304162 DOI: 10.1021/acs.jmedchem.6b01718] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A high-throughput screen (HTS) was undertaken against the respiratory chain dehydrogenase component, NADH:menaquinone oxidoreductase (Ndh) of Mycobacterium tuberculosis (Mtb). The 11000 compounds were selected for the HTS based on the known phenothiazine Ndh inhibitors, trifluoperazine and thioridazine. Combined HTS (11000 compounds) and in-house screening of a limited number of quinolones (50 compounds) identified ∼100 hits and four distinct chemotypes, the most promising of which contained the quinolone core. Subsequent Mtb screening of the complete in-house quinolone library (350 compounds) identified a further ∼90 hits across three quinolone subtemplates. Quinolones containing the amine-based side chain were selected as the pharmacophore for further modification, resulting in metabolically stable quinolones effective against multi drug resistant (MDR) Mtb. The lead compound, 42a (MTC420), displays acceptable antituberculosis activity (Mtb IC50 = 525 nM, Mtb Wayne IC50 = 76 nM, and MDR Mtb patient isolates IC50 = 140 nM) and favorable pharmacokinetic and toxicological profiles.
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27
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Jiang Z, Hong WD, Cui X, Gao H, Wu P, Chen Y, Shen D, Yang Y, Zhang B, Taylor MJ, Ward SA, O'Neill PM, Zhao S, Zhang K. Synthesis and structure–activity relationship of N4-benzylamine-N2-isopropyl-quinazoline-2,4-diamines derivatives as potential antibacterial agents. RSC Adv 2017. [DOI: 10.1039/c7ra10352b] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
This paper investigated the SAR of the N4-benzylamine-N2-isopropyl-quinazoline-2,4-diamines derivatives with heterocyclic scaffold which showed good activities against S. aureus, E. coli, MRSA, S. epidermidis and S. typhimurium.
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Price KE, Armstrong CM, Imlay LS, Hodge DM, Pidathala C, Roberts NJ, Park J, Mikati M, Sharma R, Lawrenson AS, Tolia NH, Berry NG, O'Neill PM, John ARO. Molecular Mechanism of Action of Antimalarial Benzoisothiazolones: Species-Selective Inhibitors of the Plasmodium spp. MEP Pathway enzyme, IspD. Sci Rep 2016; 6:36777. [PMID: 27857147 PMCID: PMC5114681 DOI: 10.1038/srep36777] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Accepted: 10/20/2016] [Indexed: 01/10/2023] Open
Abstract
The methylerythritol phosphate (MEP) pathway is an essential metabolic pathway found in malaria parasites, but absent in mammals, making it a highly attractive target for the discovery of novel and selective antimalarial therapies. Using high-throughput screening, we have identified 2-phenyl benzo[d]isothiazol-3(2H)-ones as species-selective inhibitors of Plasmodium spp. 2-C-methyl-D-erythritol-4-phosphate cytidyltransferase (IspD), the third catalytic enzyme of the MEP pathway. 2-Phenyl benzo[d]isothiazol-3(2H)-ones display nanomolar inhibitory activity against P. falciparum and P. vivax IspD and prevent the growth of P. falciparum in culture, with EC50 values below 400 nM. In silico modeling, along with enzymatic, genetic and crystallographic studies, have established a mechanism-of-action involving initial non-covalent recognition of inhibitors at the IspD binding site, followed by disulfide bond formation through attack of an active site cysteine residue on the benzo[d]isothiazol-3(2H)-one core. The species-selective inhibitory activity of these small molecules against Plasmodium spp. IspD and cultured parasites suggests they have potential as lead compounds in the pursuit of novel drugs to treat malaria.
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29
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Ismail HM, Barton VE, Panchana M, Charoensutthivarakul S, Biagini GA, Ward SA, O'Neill PM. Berichtigung: A Click Chemistry-Based Proteomic Approach Reveals that 1,2,4-Trioxolane and Artemisinin Antimalarials Share a Common Protein Alkylation Profile. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201607032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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30
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Ismail HM, Barton VE, Panchana M, Charoensutthivarakul S, Biagini GA, Ward SA, O'Neill PM. Corrigendum: A Click Chemistry-Based Proteomic Approach Reveals that 1,2,4-Trioxolane and Artemisinin Antimalarials Share a Common Protein Alkylation Profile. Angew Chem Int Ed Engl 2016; 55:10548. [PMID: 27552550 DOI: 10.1002/anie.201607032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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31
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Ismail HM, Barton VE, Panchana M, Charoensutthivarakul S, Biagini GA, Ward SA, O'Neill PM. A Click Chemistry-Based Proteomic Approach Reveals that 1,2,4-Trioxolane and Artemisinin Antimalarials Share a Common Protein Alkylation Profile. ANGEWANDTE CHEMIE (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2016; 128:6511-6515. [PMID: 27397940 PMCID: PMC4934454 DOI: 10.1002/ange.201512062] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Revised: 02/19/2016] [Indexed: 12/12/2022]
Abstract
In spite of the recent increase in endoperoxide antimalarials under development, it remains unclear if all these chemotypes share a common mechanism of action. This is important since it will influence cross-resistance risks between the different classes. Here we investigate this proposition using novel clickable 1,2,4-trioxolane activity based protein-profiling probes (ABPPs). ABPPs with potent antimalarial activity were able to alkylate protein target(s) within the asexual erythrocytic stage of Plasmodium falciparum (3D7). Importantly, comparison of the alkylation fingerprint with that generated from an artemisinin ABPP equivalent confirms a highly conserved alkylation profile, with both endoperoxide classes targeting proteins in the glycolytic, hemoglobin degradation, antioxidant defence, protein synthesis and protein stress pathways, essential biological processes for plasmodial survival. The alkylation signatures of the two chemotypes show significant overlap (ca. 90 %) both qualitatively and semi-quantitatively, suggesting a common mechanism of action that raises concerns about potential cross-resistance liabilities.
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32
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Ismail HM, Barton VE, Panchana M, Charoensutthivarakul S, Biagini GA, Ward SA, O'Neill PM. A Click Chemistry-Based Proteomic Approach Reveals that 1,2,4-Trioxolane and Artemisinin Antimalarials Share a Common Protein Alkylation Profile. Angew Chem Int Ed Engl 2016; 55:6401-5. [PMID: 27089538 PMCID: PMC4934138 DOI: 10.1002/anie.201512062] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Revised: 02/19/2016] [Indexed: 12/11/2022]
Abstract
In spite of the recent increase in endoperoxide antimalarials under development, it remains unclear if all these chemotypes share a common mechanism of action. This is important since it will influence cross-resistance risks between the different classes. Here we investigate this proposition using novel clickable 1,2,4-trioxolane activity based protein-profiling probes (ABPPs). ABPPs with potent antimalarial activity were able to alkylate protein target(s) within the asexual erythrocytic stage of Plasmodium falciparum (3D7). Importantly, comparison of the alkylation fingerprint with that generated from an artemisinin ABPP equivalent confirms a highly conserved alkylation profile, with both endoperoxide classes targeting proteins in the glycolytic, hemoglobin degradation, antioxidant defence, protein synthesis and protein stress pathways, essential biological processes for plasmodial survival. The alkylation signatures of the two chemotypes show significant overlap (ca. 90 %) both qualitatively and semi-quantitatively, suggesting a common mechanism of action that raises concerns about potential cross-resistance liabilities.
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33
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Shore ER, Awais M, Kershaw NM, Gibson RR, Pandalaneni S, Latawiec D, Wen L, Javed MA, Criddle DN, Berry N, O'Neill PM, Lian LY, Sutton R. Small Molecule Inhibitors of Cyclophilin D To Protect Mitochondrial Function as a Potential Treatment for Acute Pancreatitis. J Med Chem 2016; 59:2596-611. [PMID: 26950392 DOI: 10.1021/acs.jmedchem.5b01801] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Opening of the mitochondrial permeability transition pore (MPTP) causes mitochondrial dysfunction and necrosis in acute pancreatitis (AP), a condition without specific drug treatment. Cyclophilin D (CypD) is a mitochondrial matrix peptidyl-prolyl isomerase that regulates the MPTP and is a drug target for AP. We have synthesized urea-based small molecule inhibitors of cyclophilins and tested them against CypD using binding and isomerase activity assays. Thermodynamic profiles of the CypD/inhibitor interactions were determined by isothermal titration calorimetry. Seven new high-resolution crystal structures of CypD-inhibitor complexes were obtained to guide compound optimization. Compounds 4, 13, 14, and 19 were tested in freshly isolated murine pancreatic acinar cells (PACs) to determine inhibition of toxin-induced loss of mitochondrial membrane potential (ΔΨm) and necrotic cell death pathway activation. Compound 19 was found to have a Kd of 410 nM and a favorable thermodynamic profile, and it showed significant protection of ΔΨm and reduced necrosis of murine as well as human PACs. Compound 19 holds significant promise for future lead optimization.
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34
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Wong MHL, Bryan HK, Copple IM, Jenkins RE, Chiu PH, Bibby J, Berry NG, Kitteringham NR, Goldring CE, O'Neill PM, Park BK. Design and Synthesis of Irreversible Analogues of Bardoxolone Methyl for the Identification of Pharmacologically Relevant Targets and Interaction Sites. J Med Chem 2016; 59:2396-409. [PMID: 26908173 DOI: 10.1021/acs.jmedchem.5b01292] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Semisynthetic triterpenoids such as bardoxolone methyl (methyl-2-cyano 3,12-dioxooleano-1,9-dien-28-oate; CDDO-Me) (4) are potent inducers of antioxidant and anti-inflammatory signaling pathways, including those regulated by the transcription factor Nrf2. However, the reversible nature of the interaction between triterpenoids and thiols has hindered attempts to identify pharmacologically relevant targets and characterize the sites of interaction. Here, we report a shortened synthesis and SAR profiling of 4, enabling the design of analogues that react irreversibly with model thiols, as well as the model protein glutathione S-transferase P1, in vitro. We show that one of these analogues, CDDO-epoxide (13), is comparable to 4 in terms of cytotoxicity and potency toward Nrf2 in rat hepatoma cells and stably modifies specific cysteine residues (namely, Cys-257, -273, -288, -434, -489, and -613) within Keap1, the major repressor of Nrf2, both in vitro and in living cells. Supported by molecular modeling, these data demonstrate the value of 13 for identifying site(s) of interaction with pharmacologically relevant targets and informing the continuing development of triterpenoids as novel drug candidates.
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35
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Horta P, Kuş N, Henriques MSC, Paixão JA, Coelho L, Nogueira F, O'Neill PM, Fausto R, Cristiano MLS. Quinolone-Hydroxyquinoline Tautomerism in Quinolone 3-Esters. Preserving the 4-Oxoquinoline Structure To Retain Antimalarial Activity. J Org Chem 2015; 80:12244-57. [PMID: 26551438 DOI: 10.1021/acs.joc.5b02169] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recent publications report in vitro activity of quinolone 3-esters against the bc1 protein complex of Plasmodium falciparum and the parasite. Docking studies performed in silico at the yeast Qo site established a key role for the 4-oxo and N-H groups in drug-target interactions. Thus, the possibility of 4-oxoquinoline/4-hydroxyquinoline tautomerism may impact in pharmacologic profiles and should be investigated. We describe the synthesis, structure, photochemistry, and activity against multidrug-resistant P. falciparum strain Dd2 of ethyl 4-oxo-7-methylquinoline-3-carboxylate (7Me-OQE) and ethyl 4-hydroxy-5-methylquinoline-3-carboxylate (5Me-HQE), obtained from diethyl 2-[((3-methylphenyl)amino)methylene]malonate. Theoretically (B3LYP/6-311++G(d,p)), 5Me-HQE and 7Me-OQE show clear preference for the hydroxyquinoline form. The difference between the lowest energy hydroxyquinoline and quinolone forms is 27 and 38 kJ mol(-1), for 5Me-HQE and 7Me-OQE, respectively. Calculations of aromaticity indexes show that in 5Me-HQE both rings are aromatic, while in the corresponding oxo tautomers the nitrogen-containing ring is essentially non-aromatic. The structure of monomeric 5Me-HQE was studied using matrix isolation coupled to FTIR spectroscopy. No traces of 4-oxoquinoline tautomers were found in the experimental IR spectra, revealing that the species present in the crystal, 5Me-HQE·HCl, was lost HCl upon sublimation but did not tautomerize. Continuous broadband irradiation (λ > 220 nm; 130 min) of the matrix led to only partial photodecomposition of 5Me-HQE (ca. 1/3).
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36
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O'Neill PM, Ward SA. Ein Chinolincarboxamid als Breitbandwirkstoff gegen Malaria: Angriff in drei parasitären Stadien. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201507264] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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37
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O'Neill PM, Ward SA. A Quinoline Carboxamide Antimalarial Drug Candidate Uniquely Targets Plasmodia at Three Stages of the Parasite Life Cycle. Angew Chem Int Ed Engl 2015; 54:13504-6. [PMID: 26426264 DOI: 10.1002/anie.201507264] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Indexed: 11/05/2022]
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38
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McConville M, Fernández J, Angulo-Barturen Í, Bahamontes-Rosa N, Ballell-Pages L, Castañeda P, de Cózar C, Crespo B, Guijarro L, Jiménez-Díaz MB, Martínez-Martínez MS, de Mercado J, Santos-Villarejo Á, Sanz LM, Frigerio M, Washbourn G, Ward SA, Nixon GL, Biagini GA, Berry NG, Blackman MJ, Calderón F, O'Neill PM. Carbamoyl Triazoles, Known Serine Protease Inhibitors, Are a Potent New Class of Antimalarials. J Med Chem 2015. [PMID: 26222445 DOI: 10.1021/acs.jmedchem.5b00434] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Screening of the GSK corporate collection, some 1.9 million compounds, against Plasmodium falciparum (Pf), revealed almost 14000 active hits that are now known as the Tres Cantos Antimalarial Set (TCAMS). Followup work by Calderon et al. clustered and computationally filtered the TCAMS through a variety of criteria and reported 47 series containing a total of 522 compounds. From this enhanced set, we identified the carbamoyl triazole TCMDC-134379 (1), a known serine protease inhibitor, as an excellent starting point for SAR profiling. Lead optimization of 1 led to several molecules with improved antimalarial potency, metabolic stabilities in mouse and human liver microsomes, along with acceptable cytotoxicity profiles. Analogue 44 displayed potent in vitro activity (IC50 = 10 nM) and oral activity in a SCID mouse model of Pf infection with an ED50 of 100 and ED90 of between 100 and 150 mg kg(-1), respectively. The results presented encourage further investigations to identify the target of these highly active compounds.
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39
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Eckle VS, Grasshoff C, Mirakaj V, O'Neill PM, Berry NG, Leuwer M, Antkowiak B. 4-bromopropofol decreases action potential generation in spinal neurons by inducing a glycine receptor-mediated tonic conductance. Br J Pharmacol 2015; 171:5790-801. [PMID: 25131750 DOI: 10.1111/bph.12880] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 07/29/2014] [Accepted: 08/11/2014] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND AND PURPOSE Impaired function of spinal strychnine-sensitive glycine receptors gives rise to chronic pain states and movement disorders. Therefore, increased activity of glycine receptors should help to treat such disorders. Although compounds targeting glycine receptors with a high selectivity are lacking, halogenated analogues of propofol have recently been considered as potential candidates. Therefore we asked whether 4-bromopropofol attenuated the excitability of spinal neurons by promoting glycine receptor-dependent inhibition. EXPERIMENTAL APPROACH The actions of sub-anaesthetic concentrations of propofol and 4-bromopropofol were investigated in spinal tissue cultures prepared from mice. Drug-induced alterations in action potential firing were monitored by extracellular multi-unit recordings. The effects on GABAA and glycine receptor-mediated inhibition were quantified by whole-cell voltage-clamp recordings. KEY RESULTS Low concentrations of 4-bromopropofol (50 nM) reduced action potential activity of ventral horn neurons by about 30%, compared with sham-treated slices. This effect was completely abolished by strychnine (1 μM). In voltage-clamped neurons, 4-bromopropofol activated glycine receptors, generating a tonic current of 65 ± 10 pA, while GABAA - and glycine receptor-mediated synaptic transmission remained unaffected. CONCLUSIONS AND IMPLICATIONS The highest glycine levels in the CNS are found in the ventral horn of the spinal cord, a region mediating pain-induced motor reflexes and participating in the control of muscle tone. 4-Bromopropofol may serve as a starting point for the development of non-sedative, non-addictive, muscle relaxants and analgesics to be used to treat low back pain.
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40
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Charoensutthivarakul S, David Hong W, Leung SC, Gibbons PD, Bedingfield PTP, Nixon GL, Lawrenson AS, Berry NG, Ward SA, Biagini GA, O'Neill PM. 2-Pyridylquinolone
antimalarials with improved antimalarial activity and physicochemical properties. MEDCHEMCOMM 2015. [DOI: 10.1039/c5md00062a] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
2-Pyridylquinolones with improved solubility, an improved metabolic stability profile, reduced off-target toxicity and 12 nM Plasmodium falciparum antimalarial activity are described.
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41
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Kershaw NM, Wright GSA, Sharma R, Antonyuk SV, Strange RW, Berry NG, O'Neill PM, Hasnain SS. X-ray crystallography and computational docking for the detection and development of protein-ligand interactions. Curr Med Chem 2014; 20:569-75. [PMID: 23278398 DOI: 10.2174/0929867311320040008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 12/13/2012] [Accepted: 12/14/2012] [Indexed: 11/22/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterised by the selective dysfunction and death of the upper and lower motor neurons. Median survival rates are between 3 and 5 years after diagnosis. Mutations in the gene encoding Cu/Zn superoxide dismutase (SOD1) have been linked to a subset of familial forms of ALS (fALS). Herein, we describe a fragment- based drug discovery (FBDD) approach for the investigation of small molecule binding sites in SOD1. X-ray crystallography has been used as the primary screening method and has been shown to directly detect protein-ligand interactions which cannot be unambiguously identified using other biophysical methods. The structural requirements for effective binding at Trp32 are detailed for a series of quinazoline-containing compounds. The investigation of an additional site that binds a range of catecholamines and the use of computational modelling to assist fragment evolution is discussed. This study also highlights the importance of ligand solubility for successful Xray crystallographic campaigns in lead compound design.
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42
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Antoine T, Fisher N, Amewu R, O'Neill PM, Ward SA, Biagini GA. Rapid kill of malaria parasites by artemisinin and semi-synthetic endoperoxides involves ROS-dependent depolarization of the membrane potential. J Antimicrob Chemother 2013; 69:1005-16. [PMID: 24335485 PMCID: PMC3956377 DOI: 10.1093/jac/dkt486] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Objectives Artemisinin and artemisinin semi-synthetic derivatives (collectively known as endoperoxides) are first-line antimalarials for the treatment of uncomplicated and severe malaria. Endoperoxides display very fast killing rates and are generally recalcitrant to parasite resistance development. These key pharmacodynamic features are a result of a complex mechanism of action, the details of which lack consensus. Here, we report on the primary physiological events leading to parasite death. Methods Parasite mitochondrial (ΔΨm) and plasma membrane (ΔΨp) electrochemical potentials were measured using real-time single-cell imaging following exposure to pharmacologically relevant concentrations of endoperoxides (artemisinin, dihydroartemisinin, artesunate and the synthetic tetraoxane RKA182). In addition, mitochondrial electron transport chain components NADH:quinone oxidoreductase (alternative complex I), bc1 (complex III) and cytochrome oxidase (complex IV) were investigated to determine their functional sensitivity to the various endoperoxides. Results Parasite exposure to endoperoxides resulted in rapid depolarization of parasite ΔΨm and ΔΨp. The rate of depolarization was decreased in the presence of a reactive oxygen species (ROS) scavenger and Fe3+ chelators. Depolarization of ΔΨm by endoperoxides is not believed to be through the inhibition of mitochondrial electron transport chain components, owing to the lack of significant inhibition when assayed directly. Conclusions The depolarization of ΔΨm and ΔΨp is shown to be mediated via the generation of ROS that are initiated by iron bioactivation of endoperoxides and/or catalysed by iron-dependent oxidative stress. These data are discussed in the context of current hypotheses concerning the mode of action of endoperoxides.
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43
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Oliveira R, Newton AS, Guedes RC, Miranda D, Amewu RK, Srivastava A, Gut J, Rosenthal PJ, O'Neill PM, Ward SA, Lopes F, Moreira R. An Endoperoxide‐Based Hybrid Approach to Deliver Falcipain Inhibitors Inside Malaria Parasites. ChemMedChem 2013; 8:1528-36. [DOI: 10.1002/cmdc.201300202] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 06/14/2013] [Indexed: 11/09/2022]
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44
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La Pensée L, Sabbani S, Sharma R, Bhamra I, Shore E, Chadwick AE, Berry NG, Firman J, Araujo NC, Cabral L, Cristiano MLS, Bateman C, Janneh O, Gavrila A, Wu YH, Hussain A, Ward SA, Stocks PA, Cosstick R, O'Neill PM. Inside Cover: Artemisinin-Polypyrrole Conjugates: Synthesis, DNA Binding Studies and Preliminary Antiproliferative Evaluation (ChemMedChem 5/2013). ChemMedChem 2013. [DOI: 10.1002/cmdc.201390016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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45
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La Pensée L, Sabbani S, Sharma R, Bhamra I, Shore E, Chadwick AE, Berry NG, Firman J, Araujo NC, Cabral L, Cristiano MLS, Bateman C, Janneh O, Gavrila A, Wu YH, Hussain A, Ward SA, Stocks PA, Cosstick R, O'Neill PM. Artemisinin-polypyrrole conjugates: synthesis, DNA binding studies and preliminary antiproliferative evaluation. ChemMedChem 2013; 8:709-18. [PMID: 23495190 DOI: 10.1002/cmdc.201200536] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Indexed: 11/06/2022]
Abstract
Greater than the sum of its parts: Artemisinins are currently in phase I-II clinical trials against breast, colorectal and non-small-cell lung cancers. In an attempt to offer increased specificity, a series of hybrid artemisinin-polypyrrole minor groove binder conjugates are described. DNA binding/modelling studies and preliminary biological evaluation give insights into their mechanism of action and the potential of this strategy.
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46
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Nixon GL, Moss DM, Shone AE, Lalloo DG, Fisher N, O'Neill PM, Ward SA, Biagini GA. Antimalarial pharmacology and therapeutics of atovaquone. J Antimicrob Chemother 2013; 68:977-85. [PMID: 23292347 PMCID: PMC4344550 DOI: 10.1093/jac/dks504] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Atovaquone is used as a fixed-dose combination with proguanil (Malarone) for treating children and adults with uncomplicated malaria or as chemoprophylaxis for preventing malaria in travellers. Indeed, in the USA, between 2009 and 2011, Malarone prescriptions accounted for 70% of all antimalarial pre-travel prescriptions. In 2013 the patent for Malarone will expire, potentially resulting in a wave of low-cost generics. Furthermore, the malaria scientific community has a number of antimalarial quinolones with a related pharmacophore to atovaquone at various stages of pre-clinical development. With this in mind, it is timely here to review the current knowledge of atovaquone, with the purpose of aiding the decision making of clinicians and drug developers involved in the future use of atovaquone generics or atovaquone derivatives.
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47
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Elliott EC, Maggs JL, Park BK, O'Neill PM, Stachulski AV. Convenient syntheses of halo-dibenz[b,f]azepines and carbamazepine analogues via N-arylindoles. Org Biomol Chem 2013; 11:8426-34. [DOI: 10.1039/c3ob41252k] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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48
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Warman AJ, Rito TS, Fisher NE, Moss DM, Berry NG, O'Neill PM, Ward SA, Biagini GA. Antitubercular pharmacodynamics of phenothiazines. J Antimicrob Chemother 2012; 68:869-80. [PMID: 23228936 DOI: 10.1093/jac/dks483] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
OBJECTIVES Phenothiazines have been shown to exhibit in vitro and in vivo activity against Mycobacterium tuberculosis (Mtb) and multidrug-resistant Mtb. They are predicted to target the genetically validated respiratory chain component type II NADH:quinone oxidoreductase (Ndh). Using a set of compounds containing the phenothiazine pharmacophore, we have (i) investigated whether chemical validation data support the molecular target and (ii) evaluated pharmacophore tractability for further drug development. METHODS Recombinant Mtb Ndh was generated and its functionality confirmed by steady-state kinetics. Pharmacodynamic profiling of the phenothiazines, including antitubercular efficacy in aerobic and O2-limited conditions, time-kill assays and isobole analyses against first-line antituberculars, was performed. Potential mitochondrial toxicity was assessed in a modified HepG2 cell-line assay and against bovine cytochrome bc1. RESULTS Steady-state kinetic analyses revealed a substrate preference for coenzyme Q2 and an inability to utilize NADPH. A positive correlation between recombinant Ndh inhibition and kill of aerobically cultured Mtb was observed, whilst enhanced potency was demonstrated in a hypoxic model. Time-kill studies revealed the phenothiazines to be bactericidal whilst isobolograms exposed antagonism with isoniazid, indicative of intracellular NADH/NAD(+) couple perturbation. At therapeutic levels, phenothiazine-mediated toxicity was appreciable; however, specific mitochondrial targeting was excluded. CONCLUSIONS Data generated support the hypothesis that Ndh is the molecular target of phenothiazines. The favourable pharmacodynamic properties of the phenothiazines are consistent with a target product profile that includes activity against dormant/persistent bacilli, rapid bactericidal activity and activity against drug-resistant Mtb by a previously unexploited mode of action. These properties warrant further medicinal chemistry to improve potency and safety.
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Copple IM, Mercer AE, Firman J, Donegan G, Herpers B, Wong MH, Chadwick J, Bringela AD, Cristiano MLS, van de Water B, Ward SA, O'Neill PM, Park BK. Examination of the cytotoxic and embryotoxic potential and underlying mechanisms of next-generation synthetic trioxolane and tetraoxane antimalarials. Mol Med 2012; 18:1045-55. [PMID: 22669474 DOI: 10.2119/molmed.2012.00154] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Accepted: 05/22/2012] [Indexed: 11/06/2022] Open
Abstract
Semisynthetic artemisinin-based therapies are the first-line treatment for P. falciparum malaria, but next-generation synthetic drug candidates are urgently required to improve availability and respond to the emergence of artemisinin-resistant parasites. Artemisinins are embryotoxic in animal models and induce apoptosis in sensitive mammalian cells. Understanding the cytotoxic propensities of antimalarial drug candidates is crucial to their successful development and utilization. Here, we demonstrate that, similarly to the model artemisinin artesunate (ARS), a synthetic tetraoxane drug candidate (RKA182) and a trioxolane equivalent (FBEG100) induce embryotoxicity and depletion of primitive erythroblasts in a rodent model. We also show that RKA182, FBEG100 and ARS are cytotoxic toward a panel of established and primary human cell lines, with caspase-dependent apoptosis and caspase-independent necrosis underlying the induction of cell death. Although the toxic effects of RKA182 and FBEG100 proceed more rapidly and are relatively less cell-selective than that of ARS, all three compounds are shown to be dependent upon heme, iron and oxidative stress for their ability to induce cell death. However, in contrast to previously studied artemisinins, the toxicity of RKA182 and FBEG100 is shown to be independent of general chemical decomposition. Although tetraoxanes and trioxolanes have shown promise as next-generation antimalarials, the data described here indicate that adverse effects associated with artemisinins, including embryotoxicity, cannot be ruled out with these novel compounds, and a full understanding of their toxicological actions will be central to the continuing design and development of safe and effective drug candidates which could prove important in the fight against malaria.
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Fisher N, Abd Majid R, Antoine T, Al-Helal M, Warman AJ, Johnson DJ, Lawrenson AS, Ranson H, O'Neill PM, Ward SA, Biagini GA. Cytochrome b mutation Y268S conferring atovaquone resistance phenotype in malaria parasite results in reduced parasite bc1 catalytic turnover and protein expression. J Biol Chem 2012; 287:9731-9741. [PMID: 22282497 PMCID: PMC3322985 DOI: 10.1074/jbc.m111.324319] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Revised: 01/26/2012] [Indexed: 11/24/2022] Open
Abstract
Atovaquone is an anti-malarial drug used in combination with proguanil (e.g. Malarone(TM)) for the curative and prophylactic treatment of malaria. Atovaquone, a 2-hydroxynaphthoquinone, is a competitive inhibitor of the quinol oxidation (Q(o)) site of the mitochondrial cytochrome bc(1) complex. Inhibition of this enzyme results in the collapse of the mitochondrial membrane potential, disruption of pyrimidine biosynthesis, and subsequent parasite death. Resistance to atovaquone in the field is associated with point mutations in the Q(o) pocket of cytochrome b, most notably near the conserved Pro(260)-Glu(261)-Trp(262)-Tyr(263) (PEWY) region in the ef loop). The effect of this mutation has been extensively studied in model organisms but hitherto not in the parasite itself. Here, we have performed a molecular and biochemical characterization of an atovaquone-resistant field isolate, TM902CB. Molecular analysis of this strain reveals the presence of the Y268S mutation in cytochrome b. The Y268S mutation is shown to confer a 270-fold shift of the inhibitory constant (K(i)) for atovaquone with a concomitant reduction in the V(max) of the bc(1) complex of ∼40% and a 3-fold increase in the observed K(m) for decylubiquinol. Western blotting analyses reveal a reduced iron-sulfur protein content in Y268S bc(1) suggestive of a weakened interaction between this subunit and cytochrome b. Gene expression analysis of the TM902CB strain reveals higher levels of expression, compared with the 3D7 (atovaquone-sensitive) control strain in bc(1) and cytochrome c oxidase genes. It is hypothesized that the observed differential expression of these and other key genes offsets the fitness cost resulting from reduced bc(1) activity.
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