51
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Labarrios E, Jerezano A, Jiménez F, del Carmen Cruz M, Delgado F, Zepeda LG, Tamariz J. Efficient Synthetic Approach to Substituted Benzo[b]furans and Benzo[b]thiophenes by Iodine-Promoted Cyclization of Enaminones. J Heterocycl Chem 2013. [DOI: 10.1002/jhet.1686] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Ehecatl Labarrios
- Departamento de Química Orgánica, Escuela Nacional de Ciencias Biológicas; Instituto Politécnico Nacional. Prol. Carpio y Plan de Ayala; 11340 México D.F. Mexico
| | - Alberto Jerezano
- Departamento de Química Orgánica, Escuela Nacional de Ciencias Biológicas; Instituto Politécnico Nacional. Prol. Carpio y Plan de Ayala; 11340 México D.F. Mexico
| | - Fabiola Jiménez
- Centro de Investigación en Biotecnología Aplicada; Instituto Politécnico Nacional; Km 15 Carretera Sta. Inés Tecuexcomac Tepetitla 90700 Tlaxcala Mexico
| | - María del Carmen Cruz
- Centro de Investigación en Biotecnología Aplicada; Instituto Politécnico Nacional; Km 15 Carretera Sta. Inés Tecuexcomac Tepetitla 90700 Tlaxcala Mexico
| | - Francisco Delgado
- Departamento de Química Orgánica, Escuela Nacional de Ciencias Biológicas; Instituto Politécnico Nacional. Prol. Carpio y Plan de Ayala; 11340 México D.F. Mexico
| | - L. Gerardo Zepeda
- Departamento de Química Orgánica, Escuela Nacional de Ciencias Biológicas; Instituto Politécnico Nacional. Prol. Carpio y Plan de Ayala; 11340 México D.F. Mexico
| | - Joaquín Tamariz
- Departamento de Química Orgánica, Escuela Nacional de Ciencias Biológicas; Instituto Politécnico Nacional. Prol. Carpio y Plan de Ayala; 11340 México D.F. Mexico
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52
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Mugumbate G, Newton AS, Rosenthal PJ, Gut J, Moreira R, Chibale K, Guedes RC. Novel anti-plasmodial hits identified by virtual screening of the ZINC database. J Comput Aided Mol Des 2013; 27:859-71. [PMID: 24158745 DOI: 10.1007/s10822-013-9685-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 10/12/2013] [Indexed: 01/16/2023]
Abstract
Increased resistance of Plasmodium falciparum to most available drugs challenges the control of malaria. Studies with protease inhibitors have suggested important roles for the falcipain family of cysteine proteases. These enzymes act in concert with other proteases to hydrolyze host erythrocyte hemoglobin in the parasite food vacuole. In order to find potential new antimalarial drugs, we screened in silico the ZINC database using two different protocols involving structure- and ligand-based methodologies. Our search identified 19 novel low micromolar inhibitors of cultured chloroquine resistant P. falciparum. The most active compound presented an IC50 value of 0.5 μM against cultured parasites and it also inhibited the cysteine protease falcipain-2 (IC50 = 25.5 μM). These results identify novel classes of antimalarials that are structurally different from those currently in use and which can be further derivatized to deliver leads suitable for optimisation.
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Affiliation(s)
- Grace Mugumbate
- Department of Chemistry, University of Cape Town, Rondebosch, 7701, South Africa
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53
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Blocking Plasmodium falciparum development via dual inhibition of hemoglobin degradation and the ubiquitin proteasome system by MG132. PLoS One 2013; 8:e73530. [PMID: 24023882 PMCID: PMC3759421 DOI: 10.1371/journal.pone.0073530] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Accepted: 07/22/2013] [Indexed: 12/31/2022] Open
Abstract
Among key potential drug target proteolytic systems in the malaria parasite Plasmodium falciparum are falcipains, a family of hemoglobin-degrading cysteine proteases, and the ubiquitin proteasomal system (UPS), which has fundamental importance in cellular protein turnover. Inhibition of falcipains blocks parasite development, primarily due to inhibition of hemoglobin degradation that serves as a source of amino acids for parasite growth. Falcipains prefer P2 leucine in substrates and peptides, and their peptidyl inhibitors with leucine at the P2 position show potent antimalarial activity. The peptidyl inhibitor MG132 (Z-Leu-Leu-Leu-CHO) is a widely used proteasome inhibitor, which also has P2 leucine, and has also been shown to inhibit parasite development. However, the antimalarial targets of MG132 are unclear. We investigated whether MG132 blocks malaria parasite development by inhibiting hemoglobin degradation and/or by targeting the UPS. P. falciparum was cultured with inhibitors of the UPS (MG132, epoxomicin, and lactacystin) or falcipains (E64), and parasites were assessed for morphologies, extent of hemoglobin degradation, and accumulation of ubiquitinated proteins. MG132, like E64 and unlike epoxomicin or lactacystin, blocked parasite development, with enlargement of the food vacuole and accumulation of undegraded hemoglobin, indicating inhibition of hemoglobin degradation by MG132, most likely due to inhibition of hemoglobin-degrading falcipain cysteine proteases. Parasites cultured with epoxomicin or MG132 accumulated ubiquitinated proteins to a significantly greater extent than untreated or E64-treated parasites, indicating that MG132 inhibits the parasite UPS as well. Consistent with these findings, MG132 inhibited both cysteine protease and UPS activities present in soluble parasite extracts, and it strongly inhibited recombinant falcipains. MG132 was highly selective for inhibition of P. falciparum (IC50 0.0476 µM) compared to human peripheral blood mononuclear cells (IC50 10.8 µM). Thus, MG132 inhibits two distinct proteolytic systems in P. falciparum, and it may serve as a lead molecule for development of dual-target inhibitors of malaria parasites.
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54
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Chang M, Liu S, Huang K, Zhang X. Direct Catalytic Asymmetric Reductive Amination of Simple Aromatic Ketones. Org Lett 2013; 15:4354-7. [DOI: 10.1021/ol401851c] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Mingxin Chang
- Department of Chemistry and Chemical Biology & Department of Medicinal Chemistry, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Shaodong Liu
- Department of Chemistry and Chemical Biology & Department of Medicinal Chemistry, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Kexuan Huang
- Department of Chemistry and Chemical Biology & Department of Medicinal Chemistry, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
| | - Xumu Zhang
- Department of Chemistry and Chemical Biology & Department of Medicinal Chemistry, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States
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55
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Hu FC, Wang SW, Planells M, Robertson N, Padhy H, Du BS, Chi Y, Yang PF, Lin HW, Lee GH, Chou PT. Design of Os(II) -based sensitizers for dye-sensitized solar cells: influence of heterocyclic ancillaries. CHEMSUSCHEM 2013; 6:1366-1375. [PMID: 23843354 DOI: 10.1002/cssc.201300417] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Indexed: 06/02/2023]
Abstract
A series of Os(II) sensitizers (TFOS-x, in which x=1, 2, or 3) with a single 4,4'-dicarboxy-2,2'-dipyridine (H2 dcbpy) anchor and two chelating 2-pyridyl (or 2-pyrimidyl) triazolate ancillaries was successfully prepared. Single-crystal X-ray structural analysis showed that the core geometry of the Os(II) -based sensitizers consisted of one H2 dcbpy unit and two eclipsed cis-triazolate fragments; this was notably different from the Ru(II) -based counterparts, in which the azolate (both pyrazolate and triazolate) fragments are located at the mutual trans-positions. The basic properties were extensively probed by using spectroscopic and electrochemical methods as well as time-dependent density functional theory (TD-DFT) calculations. Fabrication of dye-sensitized solar cells (DSCs) was then attempted by using the I(-) /I3 (-) -based electrolyte solution. One such DSC device, which utilized TFOS-2 as the sensitizer, showed promising performance characteristics with a short-circuit current density (JSC ) of 15.7 mA cm(-2) , an open-circuit voltage of 610 mV, a fill factor of 0.63, and a power conversion efficiency of 6.08 % under AM 1.5G simulated one-sun irradiation. Importantly, adequate incident photon-to-current conversion efficiency performances were observed for all TFOS derivatives over the wide spectral region of 450 to 950 nm, showing a panchromatic light harvesting capability that extended into the near-infrared regime. Our results underlined a feasible strategy for maximizing JSC and increasing the efficiency of DSCs.
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Affiliation(s)
- Fa-Chun Hu
- Department of Chemistry and Low Carbon Energy Research Center, National Tsing Hua University, Hsinchu 30013 Taiwan
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56
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Tukulula M, Njoroge M, Mugumbate GC, Gut J, Rosenthal PJ, Barteau S, Streckfuss J, Heudi O, Kameni-Tcheudji J, Chibale K. Tetrazole-based deoxyamodiaquines: synthesis, ADME/PK profiling and pharmacological evaluation as potential antimalarial agents. Bioorg Med Chem 2013; 21:4904-13. [PMID: 23896611 DOI: 10.1016/j.bmc.2013.06.067] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 06/19/2013] [Accepted: 06/28/2013] [Indexed: 10/26/2022]
Abstract
A series of new deoxyamodiaquine-based compounds was synthesized via the modified TMSN3-Ugi multi-component reaction and evaluated in vitro for antiplasmodial activity. The most potent compounds, 6b, 6c and 6j, showed IC50 values in the range of 6-77nM against chloroquine-resistant K1- and W2-strains of Plasmodium falciparum. In vitro ADME characterization of frontrunner compounds 6b and 6c indicates that these two compounds are rapidly metabolized and have a high clearance rate in human and rat liver microsomes. This result correlated well with an in vivo pharmacokinetics study, which showed low bioavailability of 6c in rats. Tentative metabolite identification was determined by LC-MS and suggested metabolic lability of groups attached to the tertiary nitrogen. Preliminary studies on 6b and 6c suggested strong inhibitory activity against the major CYP450 enzymes. In silico docking studies were used to rationalize strong inhibition of CYP3A4 by 6c. Full characterization and biological evaluation of the metabolites is currently underway in our laboratories.
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57
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Biamonte MA, Wanner J, Le Roch KG. Recent advances in malaria drug discovery. Bioorg Med Chem Lett 2013; 23:2829-43. [PMID: 23587422 PMCID: PMC3762334 DOI: 10.1016/j.bmcl.2013.03.067] [Citation(s) in RCA: 129] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Revised: 03/11/2013] [Accepted: 03/20/2013] [Indexed: 01/18/2023]
Abstract
This digest covers some of the most relevant progress in malaria drug discovery published between 2010 and 2012. There is an urgent need to develop new antimalarial drugs. Such drugs can target the blood stage of the disease to alleviate the symptoms, the liver stage to prevent relapses, and the transmission stage to protect other humans. The pipeline for the blood stage is becoming robust, but this should not be a source of complacency, as the current therapies set a high standard. Drug discovery efforts directed towards the liver and transmission stages are in their infancy but are receiving increasing attention as targeting these stages could be instrumental in eradicating malaria.
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Affiliation(s)
- Marco A Biamonte
- Drug Discovery for Tropical Diseases, Suite 230, San Diego, CA 92121, USA.
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58
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Ehmke V, Winkler E, Banner DW, Haap W, Schweizer WB, Rottmann M, Kaiser M, Freymond C, Schirmeister T, Diederich F. Optimization of triazine nitriles as rhodesain inhibitors: structure-activity relationships, bioisosteric imidazopyridine nitriles, and X-ray crystal structure analysis with human cathepsin L. ChemMedChem 2013; 8:967-75. [PMID: 23658062 DOI: 10.1002/cmdc.201300112] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Indexed: 11/10/2022]
Abstract
The cysteine protease rhodesain of Trypanosoma brucei parasites causing African sleeping sickness has emerged as a target for the development of new drug candidates. Based on a triazine nitrile moiety as electrophilic headgroup, optimization studies on the substituents for the S1, S2, and S3 pockets of the enzyme were performed using structure-based design and resulted in inhibitors with inhibition constants in the single-digit nanomolar range. Comprehensive structure-activity relationships clarified the binding preferences of the individual pockets of the active site. The S1 pocket tolerates various substituents with a preference for flexible and basic side chains. Variation of the S2 substituent led to high-affinity ligands with inhibition constants down to 2 nM for compounds bearing cyclohexyl substituents. Systematic investigations on the S3 pocket revealed its potential to achieve high activities with aromatic vectors that undergo stacking interactions with the planar peptide backbone forming part of the pocket. X-ray crystal structure analysis with the structurally related enzyme human cathepsin L confirmed the binding mode of the triazine ligand series as proposed by molecular modeling. Sub-micromolar inhibition of the proliferation of cultured parasites was achieved for ligands decorated with the best substituents identified through the optimization cycles. In cell-based assays, the introduction of a basic side chain on the inhibitors resulted in a 35-fold increase in antitrypanosomal activity. Finally, bioisosteric imidazopyridine nitriles were studied in order to prevent off-target effects with unselective nucleophiles by decreasing the inherent electrophilicity of the triazine nitrile headgroup. Using this ligand, the stabilization by intramolecular hydrogen bonding of the thioimidate intermediate, formed upon attack of the catalytic cysteine residue, compensates for the lower reactivity of the headgroup. The imidazopyridine nitrile ligand showed excellent stability toward the thiol nucleophile glutathione in a quantitative in vitro assay and fourfold lower cytotoxicity than the parent triazine nitrile.
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Affiliation(s)
- Veronika Ehmke
- Laboratorium für Organische Chemie, ETH Zürich, Zürich, Switzerland
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59
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Marques AF, Esser D, Rosenthal PJ, Kassack MU, Lima LMTR. Falcipain-2 inhibition by suramin and suramin analogues. Bioorg Med Chem 2013; 21:3667-73. [PMID: 23680445 DOI: 10.1016/j.bmc.2013.04.047] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Revised: 04/09/2013] [Accepted: 04/17/2013] [Indexed: 10/26/2022]
Abstract
Falcipain-2 is a cysteine protease of the malaria parasite Plasmodium falciparum that plays a key role in the hydrolysis of hemoglobin, a process that is required by intraerythrocytic parasites to obtain amino acids. In this work we show that the polysulfonated napthylurea suramin is capable of binding to falcipain-2, inhibiting its catalytic activity at nanomolar concentrations against both synthetic substrates and the natural substrate hemoglobin. Kinetic measurements suggest that the inhibition occurs through an noncompetitive allosteric mechanism, eliciting substrate inhibition. Smaller suramin analogues and those with substituted methyl groups also showed inhibition within the nanomolar range. Our results identify the suramin family as a potential starting point for the design of falcipain-2 inhibitor antimalarials that act through a novel inhibition mechanism.
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Affiliation(s)
- Adriana Fonseca Marques
- Laboratory for Pharmaceutical Biotechnology, School of Pharmacy, Federal University of Rio de Janeiro, CCS, Bss34, Ilha do Fundão, 21941-590 Rio de Janeiro, RJ, Brazil
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60
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Lu X, Altharawi A, Gut J, Rosenthal PJ, Long TE. 1,4-naphthoquinone cations as antiplasmodial agents: hydroxy-, acyloxy-, and alkoxy-substituted analogues. ACS Med Chem Lett 2012; 3:1029-33. [PMID: 24936235 DOI: 10.1021/ml300242v] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Accepted: 10/01/2012] [Indexed: 11/28/2022] Open
Abstract
Cations of hydroxy-substituted 1,4-naphthoquinones were synthesized and evaluated as antiplasmodial agents against Plasmodium falciparum. The atovaquone analogues were found to be inactive as antagonists of parasite growth, which was attributed to ionization of the acidic hydroxyl moiety. Upon modification to an alkoxy substituent, the antiplasmodial activity was restored in the sub-100 nM range. Optimal inhibitors were found to possess IC50 values of 17.4-49.5 nM against heteroresistant P. falciparum W2.
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Affiliation(s)
- Xiao Lu
- Department
of Pharmaceutical
and Biomedical Sciences, University of Georgia, Athens, Georgia 30602, United States
| | - Ali Altharawi
- Department
of Pharmaceutical
and Biomedical Sciences, University of Georgia, Athens, Georgia 30602, United States
| | - Jiri Gut
- Department of Medicine, San
Francisco General Hospital, University of California, San Francisco, Box 0811, San Francisco, California 94143,
United States
| | - Philip J. Rosenthal
- Department of Medicine, San
Francisco General Hospital, University of California, San Francisco, Box 0811, San Francisco, California 94143,
United States
| | - Timothy E. Long
- Department
of Pharmaceutical
and Biomedical Sciences, University of Georgia, Athens, Georgia 30602, United States
- Center for
Drug Discovery, University of Georgia,
Athens, Georgia 30602, United
States
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61
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Mane UR, Gupta RC, Nadkarni SS, Giridhar RR, Naik PP, Yadav MR. Falcipain inhibitors as potential therapeutics for resistant strains of malaria: a patent review. Expert Opin Ther Pat 2012; 23:165-87. [DOI: 10.1517/13543776.2013.743992] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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62
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1,4-Addition of an aryllithium reagent to diethyl ketomalonate. Scalable synthesis of ethyl 1-(hydroxymethyl)-1,3-dihydroisobenzofuran-1-carboxylate. Tetrahedron Lett 2012. [DOI: 10.1016/j.tetlet.2012.05.052] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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63
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Vermeire JJ, Lantz LD, Caffrey CR. Cure of hookworm infection with a cysteine protease inhibitor. PLoS Negl Trop Dis 2012; 6:e1680. [PMID: 22802972 PMCID: PMC3389033 DOI: 10.1371/journal.pntd.0001680] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Accepted: 04/27/2012] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND Hookworm disease is a major global health problem and principal among a number of soil-transmitted helminthiases (STHs) for the chronic disability inflicted that impacts both personal and societal productivity. Mass drug administration most often employs single-dose therapy with just two drugs of the same chemical class to which resistance is a growing concern. New chemical entities with the appropriate single-dose efficacy are needed. METHODS AND FINDINGS Using various life-cycle stages of the hookworm Ancylostoma ceylanicum in vitro and a hamster model of infection, we report the potent, dose-dependent cidal activities of the peptidyl cysteine protease inhibitors (CPIs) K11002 (4-mopholino-carbonyl-phenylalanyl-homophenylalanyl- vinyl sulfone phenyl) and K11777 (N-methylpiperazine-phenylalanyl-homophenylalanyl-vinylsulfone phenyl). The latter is in late pre-clinical testing for submission as an Investigational New Drug (IND) with the US Federal Drug Administration as an anti-chagasic. In vitro, K11002 killed hookworm eggs but was without activity against first-stage larvae. The reverse was true for K11777 with a larvicidal potency equal to that of the current anti-hookworm drug, albendazole (ABZ). Both CPIs produced morbidity in ex vivo adult hookworms with the activity of K11777 again being at least the equivalent of ABZ. Combinations of either CPI with ABZ enhanced morbidity compared to single compounds. Strikingly, oral treatment of infected hamsters with 100 mg/kg K11777 b.i.d. (i.e., a total daily dose of 200 mg/kg) for one day cured infection: a single 100 mg/kg treatment removed >90% of worms. Treatment also reversed the otherwise fatal decrease in blood hemoglobin levels and body weights of hosts. Consistent with its mechanism of action, K11777 decreased by >95% the resident CP activity in parasites harvested from hamsters 8 h post-treatment with a single 100 mg/kg oral dose. CONCLUSION A new, oral single-dose anthelmintic that is active in an animal model of hookworm infection and that possesses a distinct mechanism of action from current anthelmintics is discovered. The data highlight both the possibility of repurposing the anti-chagasic K11777 as a treatment for hookworm infection and the opportunity to further develop CPIs as a novel anthelmintic class to target hookworms and, possibly, other helminths.
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Affiliation(s)
- Jon J. Vermeire
- Department of Pediatrics, Section of Infectious Diseases, Yale University School of Medicine, New Haven, Connecticut
| | - Lorine D. Lantz
- Department of Pediatrics, Section of Infectious Diseases, Yale University School of Medicine, New Haven, Connecticut
| | - Conor R. Caffrey
- Sandler Center for Drug Discovery, California Institute for Quantitative Biosciences and the Department of Pathology, University of California, San Francisco, San Francisco, California
- * E-mail:
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64
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Pérez BC, Teixeira C, Figueiras M, Gut J, Rosenthal PJ, Gomes JRB, Gomes P. Novel cinnamic acid/4-aminoquinoline conjugates bearing non-proteinogenic amino acids: towards the development of potential dual action antimalarials. Eur J Med Chem 2012; 54:887-99. [PMID: 22683112 DOI: 10.1016/j.ejmech.2012.05.022] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 05/11/2012] [Accepted: 05/15/2012] [Indexed: 12/25/2022]
Abstract
A series of cinnamic acid/4-aminoquinoline conjugates conceived to link, through a proper retro-enantio dipeptide, a heterocyclic core known to prevent hemozoin formation, to a trans-cinnamic acid motif capable of inhibiting enzyme catalytic Cys residues, were synthesized as potential dual-action antimalarials. The effect of amino acid configuration and the absence of the dipeptide spacer were also assessed. The replacement of the D-amino acids by their natural L counterparts led to a decrease in both anti-plasmodial and falcipain-inhibitory activity, suggesting that the former are preferable. Molecules with such spacer were active against blood-stage Plasmodium falciparum, in vitro, and hemozoin formation, implying that the dipeptide has a key role in mediating these two activities. In turn, compounds without spacer were better falcipain-2 inhibitors, likely because these compounds are smaller and have their vinyl bonds in closer vicinity to the catalytic Cys, as suggested by molecular modeling calculations. These novel conjugates constitute promising leads for the development of new antiplasmodials targeted at blood-stage malaria parasites.
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Affiliation(s)
- Bianca C Pérez
- Centro de Investigação em Química da Universidade do Porto, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, R. do Campo Alegre, 687, P-4169-007 Porto, Portugal
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65
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Shah F, Gut J, Legac J, Shivakumar D, Sherman W, Rosenthal PJ, Avery MA. Computer-aided drug design of falcipain inhibitors: virtual screening, structure-activity relationships, hydration site thermodynamics, and reactivity analysis. J Chem Inf Model 2012; 52:696-710. [PMID: 22332946 DOI: 10.1021/ci2005516] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Falcipains (FPs) are hemoglobinases of Plasmodium falciparum that are validated targets for the development of antimalarial chemotherapy. A combined ligand- and structure-based virtual screening of commercial databases was performed to identify structural analogs of virtual screening hits previously discovered in our laboratory. A total of 28 low micromolar inhibitors of FP-2 and FP-3 were identified and the structure-activity relationship (SAR) in each series was elaborated. The SAR of the compounds was unusually steep in some cases and could not be explained by a traditional analysis of the ligand-protein interactions (van der Waals, electrostatics, and hydrogen bonds). To gain further insights, a statistical thermodynamic analysis of explicit solvent in the ligand binding domains of FP-2 and FP-3 was carried out to understand the roles played by water molecules in binding of these inhibitors. Indeed, the energetics associated with the displacement of water molecules upon ligand binding explained some of the complex trends in the SAR. Furthermore, low potency of a subset of FP-2 inhibitors that could not be understood by the water energetics was explained in the context of poor chemical reactivity of the reactive centers of these compounds. The present study highlights the importance of considering energetic contributors to binding beyond traditional ligand-protein interactions.
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Affiliation(s)
- Falgun Shah
- Department of Medicinal Chemistry, School of Pharmacy, University of Mississippi, University, Mississippi 38677, USA
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66
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Long TE, Lu X, Galizzi M, Docampo R, Gut J, Rosenthal PJ. Phosphonium lipocations as antiparasitic agents. Bioorg Med Chem Lett 2012; 22:2976-9. [PMID: 22414614 DOI: 10.1016/j.bmcl.2012.02.045] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Revised: 02/09/2012] [Accepted: 02/13/2012] [Indexed: 12/30/2022]
Abstract
Phosphonium lipocations were synthesized and evaluated for inhibition of the development of Plasmodium falciparum and Trypanosoma cruzi, etiological agents of malaria and Chagas disease, respectively. Optimal phthalimides and 1,4-naphthoquinone-based lipocations were active in vitro at mid-high nM concentrations against P. falciparum and low μM concentrations against T. cruzi.
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Affiliation(s)
- Timothy E Long
- Department of Pharmaceutical and Biomedical Sciences and Center for Drug Discovery, University of Georgia, Athens, GA 30602, USA.
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67
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Ehmke V, Quinsaat JEQ, Rivera-Fuentes P, Heindl C, Freymond C, Rottmann M, Brun R, Schirmeister T, Diederich F. Tuning and predicting biological affinity: aryl nitriles as cysteine protease inhibitors. Org Biomol Chem 2012; 10:5764-8. [DOI: 10.1039/c2ob00034b] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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68
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Singh P, Singh P, Kumar M, Gut J, Rosenthal PJ, Kumar K, Kumar V, Mahajan MP, Bisetty K. Synthesis, docking and in vitro antimalarial evaluation of bifunctional hybrids derived from β-lactams and 7-chloroquinoline using click chemistry. Bioorg Med Chem Lett 2012; 22:57-61. [DOI: 10.1016/j.bmcl.2011.11.082] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2011] [Revised: 11/16/2011] [Accepted: 11/19/2011] [Indexed: 10/15/2022]
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69
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Lilburn TG, Cai H, Zhou Z, Wang Y. Protease-associated cellular networks in malaria parasite Plasmodium falciparum. BMC Genomics 2011; 12 Suppl 5:S9. [PMID: 22369208 PMCID: PMC3287505 DOI: 10.1186/1471-2164-12-s5-s9] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Background Malaria continues to be one of the most severe global infectious diseases, responsible for 1-2 million deaths yearly. The rapid evolution and spread of drug resistance in parasites has led to an urgent need for the development of novel antimalarial targets. Proteases are a group of enzymes that play essential roles in parasite growth and invasion. The possibility of designing specific inhibitors for proteases makes them promising drug targets. Previously, combining a comparative genomics approach and a machine learning approach, we identified the complement of proteases (degradome) in the malaria parasite Plasmodium falciparum and its sibling species [1-3], providing a catalog of targets for functional characterization and rational inhibitor design. Network analysis represents another route to revealing the role of proteins in the biology of parasites and we use this approach here to expand our understanding of the systems involving the proteases of P. falciparum. Results We investigated the roles of proteases in the parasite life cycle by constructing a network using protein-protein association data from the STRING database [4], and analyzing these data, in conjunction with the data from protein-protein interaction assays using the yeast 2-hybrid (Y2H) system [5], blood stage microarray experiments [6-8], proteomics [9-12], literature text mining, and sequence homology analysis. Seventy-seven (77) out of 124 predicted proteases were associated with at least one other protein, constituting 2,431 protein-protein interactions (PPIs). These proteases appear to play diverse roles in metabolism, cell cycle regulation, invasion and infection. Their degrees of connectivity (i.e., connections to other proteins), range from one to 143. The largest protease-associated sub-network is the ubiquitin-proteasome system which is crucial for protein recycling and stress response. Proteases are also implicated in heat shock response, signal peptide processing, cell cycle progression, transcriptional regulation, and signal transduction networks. Conclusions Our network analysis of proteases from P. falciparum uses a so-called guilt-by-association approach to extract sets of proteins from the proteome that are candidates for further study. Novel protease targets and previously unrecognized members of the protease-associated sub-systems provide new insights into the mechanisms underlying parasitism, pathogenesis and virulence.
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Affiliation(s)
- Timothy G Lilburn
- Department of Biology, University of Texas at San Antonio, San Antonio, TX 78249, USA
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Centenary celebrations article: Cysteine proteases of human malaria parasites. J Parasit Dis 2011; 35:94-103. [PMID: 23024488 DOI: 10.1007/s12639-011-0084-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2011] [Accepted: 11/09/2011] [Indexed: 01/07/2023] Open
Abstract
There is an urgent need for new drugs against malaria, which takes millions of lives annually. Cysteine proteases are potential new drug targets, especially when current drugs are showing resistance. Falcipains and vivapains are well characterized cysteine proteases of P. falciparum and P. vivax, respectively. Studies with cysteine protease inhibitors and manipulating cysteine proteases specific genes have suggested their roles in hemoglobin hydrolysis. In P. falciparum, falcipain-2 and falcipain-3 are major hemoglobinases that hydrolyze host erythrocyte hemoglobin in the parasite food vacuole. It is confirmed that disruption of the falcipain-2 gene led to a transient block in hemoglobin hydrolysis, and disruption of falcipain-3 gene was not possible, suggesting that protease is essential for erythrocytic parasites. On the other hand, vivapain-2, vivapain-3 and vivapain-4 are important cysteine proteases of P. vivax, which shared a number of features with falcipain-2 and falcipain-3. A recent study indicates that vivapains and aspartic protease of P. vivax works collaboratively to enhance the parasites' ability to hydrolyze host erythrocyte hemoglobin. Studies also indicate that falcipains and vivapains also hydrolyse the erythrocyte cytoskeleton proteins and involved in rupture of red blood cell. Structural and biochemical analysis of falcipains and vivapains showed that they have unique domains for specific functions. Overall, the complexes of cysteine proteases with small and macromolecular inhibitors provide structural insight to facilitate the drug design. Therefore, giving due importance to the cysteine proteases, this review will briefly focus the recent advancement in the field of cysteine proteases of human malaria parasites.
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Potshangbam AM, Tanneeru K, Reddy BM, Guruprasad L. 3D-QSAR and molecular docking studies of 2-pyrimidinecarbonitrile derivatives as inhibitors against falcipain-3. Bioorg Med Chem Lett 2011; 21:7219-23. [DOI: 10.1016/j.bmcl.2011.09.107] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Revised: 09/07/2011] [Accepted: 09/10/2011] [Indexed: 10/17/2022]
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Molecular docking and 3D-QSAR studies of falcipain inhibitors using CoMFA, CoMSIA, and Open3DQSAR. Med Chem Res 2011. [DOI: 10.1007/s00044-011-9803-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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73
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Design and evaluation of primaquine-artemisinin hybrids as a multistage antimalarial strategy. Antimicrob Agents Chemother 2011; 55:4698-706. [PMID: 21807973 DOI: 10.1128/aac.05133-11] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
It is widely accepted that the struggle against malaria depends on the development of new strategies to fight infection. The "magic bullet" thought to be necessary to reach eradication should not only provide treatment for all Plasmodium spp. that infect human red blood cells but should also eliminate the replicative and dormant liver forms of the parasite. Moreover, these goals should ideally be achieved by using different mechanisms of action so as to avoid the development of resistance. To that end, two hybrid molecules with covalently linked primaquine and artemisinin moieties were synthesized, and their effectiveness against the liver and blood stages of infection was compared in vitro and in vivo with those of the parent compounds. Both hybrids displayed enhanced in vitro activities, relative to those of the parent compounds, against Plasmodium berghei liver stages. Both compounds were about as potent as artemisinin against cultured Plasmodium falciparum (50% inhibitory concentration [IC(50)], ∼10 nM). When used to treat a murine P. berghei infection, one of the molecules displayed better efficacy than an equimolar mixture of the parent pharmacophores, leading to improved cure and survival rates. These results reveal a novel approach to the design and evaluation of antimalarials based on the covalent combination of molecules acting on different stages of the parasite life cycle.
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74
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Catalytic asymmetric hydrogenation of heterocyclic ketone-derived hydrazones, pronounced solvent effect on the inversion of configuration. Tetrahedron Lett 2011. [DOI: 10.1016/j.tetlet.2011.05.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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75
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Artemisinin activity against Plasmodium falciparum requires hemoglobin uptake and digestion. Proc Natl Acad Sci U S A 2011; 108:11405-10. [PMID: 21709259 DOI: 10.1073/pnas.1104063108] [Citation(s) in RCA: 248] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Combination regimens that include artemisinin derivatives are recommended as first line antimalarials in most countries where malaria is endemic. However, the mechanism of action of artemisinin is not fully understood and the usefulness of this drug class is threatened by reports of decreased parasite sensitivity. We treated Plasmodium falciparum for periods of a few hours to mimic clinical exposure to the short half-life artemisinins. We found that drug treatment retards parasite growth and inhibits uptake of hemoglobin, even at sublethal concentrations. We show that potent artemisinin activity is dependent on hemoglobin digestion by the parasite. Inhibition of hemoglobinase activity with cysteine protease inhibitors, knockout of the cysteine protease falcipain-2 by gene deletion, or direct deprivation of host cell lysate, significantly decreases artemisinin sensitivity. Hemoglobin digestion is also required for artemisinin-induced exacerbation of oxidative stress in the parasite cytoplasm. Arrest of hemoglobin digestion by early stage parasites provides a mechanism for surviving short-term artemisinin exposure. These insights will help in the design of new drugs and new treatment strategies to circumvent drug resistance.
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76
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Guantai EM, Ncokazi K, Egan TJ, Gut J, Rosenthal PJ, Bhampidipati R, Kopinathan A, Smith PJ, Chibale K. Enone- and chalcone-chloroquinoline hybrid analogues: in silico guided design, synthesis, antiplasmodial activity, in vitro metabolism, and mechanistic studies. J Med Chem 2011; 54:3637-49. [PMID: 21500839 PMCID: PMC3104272 DOI: 10.1021/jm200149e] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Analogues of the previously reported antimalarial hybrid compounds 8b and 12 were proposed with the aim of identifying compounds with improved solubility and retained antimalarial potency. In silico characterization predicted improved solubilities of the analogues, particularly at low pH; they retained acceptable predicted permeability properties but were predicted to be susceptible to hepatic metabolism. These analogues were synthesized and found to exhibit notable in vitro antimalarial activity. Compounds 25 and 27 were the most active of the analogues. In vitro metabolism studies indicated susceptibility of the analogues to hepatic metabolism. There was also evidence of primary glucuronidation for analogues 24-27. Presumed cis-trans isomerism of 12, 22, and 23 under in vitro metabolism assay conditions was also observed, with differences in the nature and rates of metabolism observed between isomers. Biochemical studies strongly suggested that inhibition of hemozoin formation is the primary mechanism of action of these analogues.
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Affiliation(s)
- Eric M. Guantai
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
- Division of Pharmacology, University of Cape Town, Observatory 7925, South Africa
| | - Kanyile Ncokazi
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - Timothy J. Egan
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - Jiri Gut
- Department of Medicine, San Francisco General Hospital, University of California at San Francisco, CA 94143, USA
| | - Philip J. Rosenthal
- Department of Medicine, San Francisco General Hospital, University of California at San Francisco, CA 94143, USA
| | - Ravi Bhampidipati
- Centre for Drug Candidate Optimisation, Monash Institute of Pharmaceutical Sciences, Monash University (Parkville campus), 381 Royal Parade, Parkville, VIC 3052, Australia
| | - Anitha Kopinathan
- Centre for Drug Candidate Optimisation, Monash Institute of Pharmaceutical Sciences, Monash University (Parkville campus), 381 Royal Parade, Parkville, VIC 3052, Australia
| | - Peter J. Smith
- Division of Pharmacology, University of Cape Town, Observatory 7925, South Africa
| | - Kelly Chibale
- Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
- Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Rondebosch 7701, South Africa
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77
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Ang KKH, Ratnam J, Gut J, Legac J, Hansell E, Mackey ZB, Skrzypczynska KM, Debnath A, Engel JC, Rosenthal PJ, McKerrow JH, Arkin MR, Renslo AR. Mining a cathepsin inhibitor library for new antiparasitic drug leads. PLoS Negl Trop Dis 2011; 5:e1023. [PMID: 21572521 PMCID: PMC3086806 DOI: 10.1371/journal.pntd.0001023] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Accepted: 02/14/2011] [Indexed: 01/21/2023] Open
Abstract
The targeting of parasite cysteine proteases with small molecules is emerging as a possible approach to treat tropical parasitic diseases such as sleeping sickness, Chagas' disease, and malaria. The homology of parasite cysteine proteases to the human cathepsins suggests that inhibitors originally developed for the latter may be a source of promising lead compounds for the former. We describe here the screening of a unique ∼ 2,100-member cathepsin inhibitor library against five parasite cysteine proteases thought to be relevant in tropical parasitic diseases. Compounds active against parasite enzymes were subsequently screened against cultured Plasmodium falciparum, Trypanosoma brucei brucei and/or Trypanosoma cruzi parasites and evaluated for cytotoxicity to mammalian cells. The end products of this effort include the identification of sub-micromolar cell-active leads as well as the elucidation of structure-activity trends that can guide further optimization efforts.
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Affiliation(s)
- Kenny K. H. Ang
- The Small Molecule Discovery Center, University of California San Francisco, San Francisco, California, United States of America
| | - Joseline Ratnam
- The Small Molecule Discovery Center, University of California San Francisco, San Francisco, California, United States of America
| | - Jiri Gut
- Department of Medicine, San Francisco General Hospital, University of California San Francisco, San Francisco, California, United States of America
| | - Jennifer Legac
- Department of Medicine, San Francisco General Hospital, University of California San Francisco, San Francisco, California, United States of America
| | - Elizabeth Hansell
- The Sandler Center for Drug Discovery, University of California San Francisco, San Francisco, California, United States of America
| | - Zachary B. Mackey
- The Sandler Center for Drug Discovery, University of California San Francisco, San Francisco, California, United States of America
| | - Katarzyna M. Skrzypczynska
- The Sandler Center for Drug Discovery, University of California San Francisco, San Francisco, California, United States of America
| | - Anjan Debnath
- The Sandler Center for Drug Discovery, University of California San Francisco, San Francisco, California, United States of America
| | - Juan C. Engel
- The Sandler Center for Drug Discovery, University of California San Francisco, San Francisco, California, United States of America
| | - Philip J. Rosenthal
- Department of Medicine, San Francisco General Hospital, University of California San Francisco, San Francisco, California, United States of America
| | - James H. McKerrow
- The Sandler Center for Drug Discovery, University of California San Francisco, San Francisco, California, United States of America
- Department of Pathology, University of California San Francisco, San Francisco, California, United States of America
| | - Michelle R. Arkin
- The Small Molecule Discovery Center, University of California San Francisco, San Francisco, California, United States of America
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
- * E-mail: (MRA); (ARR)
| | - Adam R. Renslo
- The Small Molecule Discovery Center, University of California San Francisco, San Francisco, California, United States of America
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
- * E-mail: (MRA); (ARR)
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Grimberg BT, Mehlotra RK. Expanding the Antimalarial Drug Arsenal-Now, But How? Pharmaceuticals (Basel) 2011; 4:681-712. [PMID: 21625331 PMCID: PMC3102560 DOI: 10.3390/ph4050681] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2011] [Revised: 04/09/2011] [Accepted: 04/19/2011] [Indexed: 01/24/2023] Open
Abstract
The number of available and effective antimalarial drugs is quickly dwindling. This is mainly because a number of drug resistance-associated mutations in malaria parasite genes, such as crt, mdr1, dhfr/dhps, and others, have led to widespread resistance to all known classes of antimalarial compounds. Unfortunately, malaria parasites have started to exhibit some level of resistance in Southeast Asia even to the most recently introduced class of drugs, artemisinins. While there is much need, the antimalarial drug development pipeline remains woefully thin, with little chemical diversity, and there is currently no alternative to the precious artemisinins. It is difficult to predict where the next generation of antimalarial drugs will come from; however, there are six major approaches: (i) re-optimizing the use of existing antimalarials by either replacement/rotation or combination approach; (ii) repurposing drugs that are currently used to treat other infections or diseases; (iii) chemically modifying existing antimalarial compounds; (iv) exploring natural sources; (v) large-scale screening of diverse chemical libraries; and (vi) through parasite genome-based ("targeted") discoveries. When any newly discovered effective antimalarial treatment is used by the populus, we must maintain constant vigilance for both parasite-specific and human-related factors that are likely to hamper its success. This article is neither comprehensive nor conclusive. Our purpose is to provide an overview of antimalarial drug resistance, associated parasite genetic factors (1. Introduction; 2. Emergence of artemisinin resistance in P. falciparum), and the antimalarial drug development pipeline (3. Overview of the global pipeline of antimalarial drugs), and highlight some examples of the aforementioned approaches to future antimalarial treatment. These approaches can be categorized into "short term" (4. Feasible options for now) and "long term" (5. Next generation of antimalarial treatment-Approaches and candidates). However, these two categories are interrelated, and the approaches in both should be implemented in parallel with focus on developing a successful, long-lasting antimalarial chemotherapy.
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Affiliation(s)
- Brian T. Grimberg
- Center for Global Health and Diseases, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA; E-Mails: (B.T.G.); (R.K.M.); Tel.: +1-216-368-6328 or +1-216-368-6172, Fax: +1-216-368-4825
| | - Rajeev K. Mehlotra
- Center for Global Health and Diseases, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA; E-Mails: (B.T.G.); (R.K.M.); Tel.: +1-216-368-6328 or +1-216-368-6172, Fax: +1-216-368-4825
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Sun Z, Wang H, Wen K, Li Y, Fan E. Solvent-Free or Low-Solvent Large-Scale Preparation of Chloropyrimidine and Analogues. J Org Chem 2011; 76:4149-53. [DOI: 10.1021/jo2003715] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Zhihua Sun
- College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201600, China
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Han Wang
- College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201600, China
| | - Kun Wen
- College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201600, China
| | - Ya Li
- College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201600, China
| | - Erkang Fan
- Department of Biochemistry, University of Washington, Seattle, Washington 98155, United States
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Shah F, Mukherjee P, Gut J, Legac J, Rosenthal PJ, Tekwani BL, Avery MA. Identification of novel malarial cysteine protease inhibitors using structure-based virtual screening of a focused cysteine protease inhibitor library. J Chem Inf Model 2011; 51:852-64. [PMID: 21428453 DOI: 10.1021/ci200029y] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Malaria, in particular that caused by Plasmodium falciparum , is prevalent across the tropics, and its medicinal control is limited by widespread drug resistance. Cysteine proteases of P. falciparum , falcipain-2 (FP-2) and falcipain-3 (FP-3), are major hemoglobinases, validated as potential antimalarial drug targets. Structure-based virtual screening of a focused cysteine protease inhibitor library built with soft rather than hard electrophiles was performed against an X-ray crystal structure of FP-2 using the Glide docking program. An enrichment study was performed to select a suitable scoring function and to retrieve potential candidates against FP-2 from a large chemical database. Biological evaluation of 50 selected compounds identified 21 diverse nonpeptidic inhibitors of FP-2 with a hit rate of 42%. Atomic Fukui indices were used to predict the most electrophilic center and its electrophilicity in the identified hits. Comparison of predicted electrophilicity of electrophiles in identified hits with those in known irreversible inhibitors suggested the soft-nature of electrophiles in the selected target compounds. The present study highlights the importance of focused libraries and enrichment studies in structure-based virtual screening. In addition, few compounds were screened against homologous human cysteine proteases for selectivity analysis. Further evaluation of structure-activity relationships around these nonpeptidic scaffolds could help in the development of selective leads for antimalarial chemotherapy.
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Affiliation(s)
- Falgun Shah
- Department of Medicinal Chemistry, School of Pharmacy, University of Mississippi , University, Mississippi 38677, USA
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81
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Rosenthal PJ. Falcipains and other cysteine proteases of malaria parasites. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 712:30-48. [PMID: 21660657 DOI: 10.1007/978-1-4419-8414-2_3] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A number of cysteine proteases of malaria parasites have been described and many more are suggested by analysis of the Plasmodium falciparum genome sequence. The best characterized of these proteases are the falcipains, a family of four papain-family enzymes. Falcipain-2 and falcipain-3 act in concert with other proteases to hydrolyze host erythrocyte hemoglobin in the parasite food vacuole. Disruption of the falcipain-2 gene led to a transient block in hemoglobin hydrolysis and parasites with increased sensitivity to protease inhibitors. Disruption of the falcipain-3 gene was not possible, strongly suggesting that this protease is essential for erythrocytic parasites. Disruption of the falcipain-1 gene did not alter development in erythrocytes, but led to decreased production of oocysts in mosquitoes. other papain-family proteases predicted by the genome sequence include dipeptidyl peptidases, a calpain homolog and serine-repeat antigens (SERAs). Dipeptidyl aminopeptidase 1 appears to be essential and localized to the food vacuole, suggesting a role in hemoglobin hydrolysis. Dipeptidyl aminopeptidase 3 appears to play a role in the rupture of erythrocytes by mature parasites. the P. falciparum calpain homolog gene could not be disrupted, suggesting that the protein is essential and a role in the parasite cell cycle has been suggested. Nine P. falciparum SERAs have cysteine protease motifs, but in some the active site cys is replaced by a Ser. Gene disruption studies suggested that SERA-5 and SERA-6 are essential. activation of SERA-5 by a serine protease seems to be required for merozoite egress from the erythrocyte. New drugs for malaria are greatly needed and cysteine proteases represent potential drug targets. cysteine protease inhibitors have demonstrated potent antimalarial effects and the optimization and testing of falcipain inhibitor antimalarials is underway.
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Affiliation(s)
- Philip J Rosenthal
- Department of Medicine, San Francisco General Hospital, University of California, San Francisco, California, USA.
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Burrows JN, Waterson D. Discovering New Medicines to Control and Eradicate Malaria. TOPICS IN MEDICINAL CHEMISTRY 2011. [DOI: 10.1007/7355_2011_14] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Ehmke V, Heindl C, Rottmann M, Freymond C, Schweizer WB, Brun R, Stich A, Schirmeister T, Diederich F. Potent and selective inhibition of cysteine proteases from Plasmodium falciparum and Trypanosoma brucei. ChemMedChem 2010; 6:273-8. [PMID: 21275051 PMCID: PMC7162187 DOI: 10.1002/cmdc.201000449] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Indexed: 11/07/2022]
Affiliation(s)
- Veronika Ehmke
- Laboratory of Organic Chemistry, ETH Zürich, Wolfgang-Pauli-Strasse 10, 8093 Zürich, Switzerland
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