51
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Rastelli G, Del Rio A, Degliesposti G, Sgobba M. Fast and accurate predictions of binding free energies using MM-PBSA and MM-GBSA. J Comput Chem 2009; 31:797-810. [PMID: 19569205 DOI: 10.1002/jcc.21372] [Citation(s) in RCA: 296] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Giulio Rastelli
- Dipartimento di Scienze Farmaceutiche, Università di Modena e Reggio Emilia, Via Campi 183, 41100 Modena, Italy.
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52
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Sathunuru R, Melendez V, Kozar MP, Lin AJ. A facile one pot synthesis of 2, 4-diamino-6-substituted s-triazine derivatives. J Heterocycl Chem 2008. [DOI: 10.1002/jhet.5570450618] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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53
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Maitarad P, Saparpakorn P, Hannongbua S, Kamchonwongpaisan S, Tarnchompoo B, Yuthavong Y. Particular interaction between pyrimethamine derivatives and quadruple mutant type dihydrofolate reductase of Plasmodium falciparum: CoMFA and quantum chemical calculations studies. J Enzyme Inhib Med Chem 2008; 24:471-9. [DOI: 10.1080/14756360802201223] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Affiliation(s)
- Phornphimon Maitarad
- 1Department of Chemistry, Faculty of Science, Kasetsart University, Bangkok, 10900, Thailand
- 2Center of Nanotechnology KU, Kasetsart University and NANOTEC Center of Excellence at Kasetsart University, Pathumthani, 12120, Thailand
| | - Patchreenart Saparpakorn
- 1Department of Chemistry, Faculty of Science, Kasetsart University, Bangkok, 10900, Thailand
- 2Center of Nanotechnology KU, Kasetsart University and NANOTEC Center of Excellence at Kasetsart University, Pathumthani, 12120, Thailand
| | - Supa Hannongbua
- 1Department of Chemistry, Faculty of Science, Kasetsart University, Bangkok, 10900, Thailand
- 2Center of Nanotechnology KU, Kasetsart University and NANOTEC Center of Excellence at Kasetsart University, Pathumthani, 12120, Thailand
| | - Sumalee Kamchonwongpaisan
- 3National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Pathumthani, 12120, Thailand
| | - Bongkoch Tarnchompoo
- 3National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Pathumthani, 12120, Thailand
| | - Yongyuth Yuthavong
- 3National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Pathumthani, 12120, Thailand
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54
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Melato S, Prosperi D, Coghi P, Basilico N, Monti D. A Combinatorial Approach to 2,4,6-Trisubstituted Triazines with Potent Antimalarial Activity: Combining Conventional Synthesis and Microwave-Assistance. ChemMedChem 2008; 3:873-6. [DOI: 10.1002/cmdc.200700344] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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55
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Schlitzer M. Antimalarial drugs - what is in use and what is in the pipeline. Arch Pharm (Weinheim) 2008; 341:149-63. [PMID: 18297679 DOI: 10.1002/ardp.200700184] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Malaria continues to be a potentially fatal threat to almost half of the world's population. In light of this threat, the armory to fight this disease is rather limited. Resistance against the most common and affordable antimalarials is widespread. Only few new drugs are in clinical development, most of them belong to long used classes of antimalarial drugs. This review will concisely cover the drugs which are currently in use, and describe the drug candidates which are in clinical evaluation.
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Affiliation(s)
- Martin Schlitzer
- Philipps-Universität, Institut für Pharmazeutische Chemie, Marburg, Germany.
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56
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Diaz DS, Kozar MP, Smith KS, Asher CO, Sousa JC, Schiehser GA, Jacobus DP, Milhous WK, Skillman DR, Shearer TW. Role of Specific Cytochrome P450 Isoforms in the Conversion of Phenoxypropoxybiguanide Analogs in Human Liver Microsomes to Potent Antimalarial Dihydrotriazines. Drug Metab Dispos 2007; 36:380-5. [DOI: 10.1124/dmd.106.013920] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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57
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Japrung D, Leartsakulpanich U, Chusacultanachai S, Yuthavong Y. Conflicting requirements of Plasmodium falciparum dihydrofolate reductase mutations conferring resistance to pyrimethamine-WR99210 combination. Antimicrob Agents Chemother 2007; 51:4356-60. [PMID: 17875995 PMCID: PMC2167985 DOI: 10.1128/aac.00577-07] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Plasmodium falciparum strains bearing quadruple mutations of dihydrofolate reductase-thymidylate synthase (PfDHFR-TS) at codons 51, 59, 108, and 164 are highly resistant to pyrimethamine (PYR), a diaminopyrimidine, but sensitive to WR99210 (WR), a cycloguanil analog, suggesting different enzyme-inhibitor binding interactions. A combination of these inhibitors to delay the onset of antifolate resistance is proposed. Using error-prone PCR, libraries of random mutants of wild-type PfDHFR and PfDHFR-TS were generated and used to transform Escherichia coli, and transformants were then selected for PYR or WR resistance. Mutants highly resistant to either PYR or WR were also generated from libraries obtained from further random mutagenesis of quadruple mutants (QM) with mutations in PfDHFR or PfDHFR-TS. For reversion mutants carrying altered residues I51N, N108S, and L164I, a further mutation of D54N was required to achieve resistance against WR, but these mutants regained sensitivity to PYR. When a combination of PYR and WR was used, fewer resistant mutants were generated from both mutant libraries using the QM gene templates. The effectiveness of the drug combination in reducing the appearance of resistance mutations is likely due to conflicting requirements for mutations conferring resistance to the two drugs. Thus, a combination of inhibitors from these two drug classes should be effective in impeding the emergence of P. falciparum resistance to antifolates.
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Affiliation(s)
- Deanpen Japrung
- BIOTEC, National Science and Technology Development Agency, 113 Paholyothin Road, Klong 1, Klong Luang, Pathumthani 12120, Thailand
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58
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Schlitzer M. Malaria Chemotherapeutics Part I: History of Antimalarial Drug Development, Currently Used Therapeutics, and Drugs in Clinical Development. ChemMedChem 2007; 2:944-86. [PMID: 17530725 DOI: 10.1002/cmdc.200600240] [Citation(s) in RCA: 179] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Since ancient times, humankind has had to struggle against the persistent onslaught of pathogenic microorganisms. Nowadays, malaria is still the most important infectious disease worldwide. Considerable success in gaining control over malaria was achieved in the 1950s and 60s through landscaping measures, vector control with the insecticide DDT, and the widespread administration of chloroquine, the most important antimalarial agent ever. In the late 1960s, the final victory over malaria was believed to be within reach. However, the parasites could not be eradicated because they developed resistance against the most widely used and affordable drugs of that time. Today, cases of malaria infections are on the rise and have reached record numbers. This review gives a short description of the malaria disease, briefly addresses the history of antimalarial drug development, and focuses on drugs currently available for malaria therapy. The present knowledge regarding their mode of action and the mechanisms of resistance are explained, as are the attempts made by numerous research groups to overcome the resistance problem within classes of existing drugs and in some novel classes. Finally, this review covers all classes of antimalarials for which at least one drug candidate is in clinical development. Antimalarial agents that are solely in early development stages will be addressed in a separate review.
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Affiliation(s)
- Martin Schlitzer
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35032 Marburg, Germany.
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59
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Integration and mining of malaria molecular, functional and pharmacological data: how far are we from a chemogenomic knowledge space? Malar J 2006; 5:110. [PMID: 17112376 PMCID: PMC1665468 DOI: 10.1186/1475-2875-5-110] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2006] [Accepted: 11/17/2006] [Indexed: 11/21/2022] Open
Abstract
The organization and mining of malaria genomic and post-genomic data is important to significantly increase the knowledge of the biology of its causative agents, and is motivated, on a longer term, by the necessity to predict and characterize new biological targets and new drugs. Biological targets are sought in a biological space designed from the genomic data from Plasmodium falciparum, but using also the millions of genomic data from other species. Drug candidates are sought in a chemical space containing the millions of small molecules stored in public and private chemolibraries. Data management should, therefore, be as reliable and versatile as possible. In this context, five aspects of the organization and mining of malaria genomic and post-genomic data were examined: 1) the comparison of protein sequences including compositionally atypical malaria sequences, 2) the high throughput reconstruction of molecular phylogenies, 3) the representation of biological processes, particularly metabolic pathways, 4) the versatile methods to integrate genomic data, biological representations and functional profiling obtained from X-omic experiments after drug treatments and 5) the determination and prediction of protein structures and their molecular docking with drug candidate structures. Recent progress towards a grid-enabled chemogenomic knowledge space is discussed.
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60
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de Beer TAP, Louw AI, Joubert F. Elucidation of sulfadoxine resistance with structural models of the bifunctional Plasmodium falciparum dihydropterin pyrophosphokinase–dihydropteroate synthase. Bioorg Med Chem 2006; 14:4433-43. [PMID: 16517168 DOI: 10.1016/j.bmc.2006.02.035] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2006] [Revised: 02/16/2006] [Accepted: 02/17/2006] [Indexed: 11/24/2022]
Abstract
Resistance of the most virulent human malaria parasite, Plasmodium falciparum, to antifolates is spreading with increasing speed, especially in Africa. Antifolate resistance is mainly caused by point mutations in the P. falciparum dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR) target proteins. Homology models of the bifunctional P. falciparum dihydropterin pyrophosphokinase-dihydropteroate synthase (PPPK-DHPS) enzyme as well as the separate domains complete with bound substrates were constructed using the crystal structures of Saccharomyces cerevisiae (PPPK-DHPS), Mycobacterium tuberculosis (DHPS), Bacillus anthracis (DHPS), and Escherichia coli (PPPK) as templates. The resulting structures were subsequently solvated and refined using molecular dynamics. The active site residues of DHPS are highly conserved in S. cerevisiae, M. tuberculosis, E. coli, S. aureus, and B. anthracis, an attribute also shared by P. falciparum DHPS. Sulfadoxine was superimposed into the equivalent position of the p-aminobenzoic acid substrate and its binding parameters were refined using minimization and molecular dynamics. Sulfadoxine appears to interact mainly with P. falciparum DHPS mainly through hydrophobic interactions. Rational explanations are provided by the model for the sulfadoxine resistance-causing effects of four of the five known mutations in P. falciparum DHPS. A possible structure for the bifunctional PPPK-DHPS was derived from the structure from the S. cerevisiae bifunctional enzyme. The active site residues of P. falciparum PPPK are also conserved when compared to S. cerevisiae, Haemophilus influenzae, and E. coli. The informative nature of these models opens up avenues for structure-based drug design approaches toward the development of alternative and more effective inhibitors of P. falciparum PPPK-DHPS.
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Affiliation(s)
- Tjaart A P de Beer
- Bioinformatics and Computational Biology Unit, Department of Biochemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, South Africa
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61
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Yuthavong Y, Kamchonwongpaisan S, Leartsakulpanich U, Chitnumsub P. Folate metabolism as a source of molecular targets for antimalarials. Future Microbiol 2006; 1:113-25. [PMID: 17661690 DOI: 10.2217/17460913.1.1.113] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Folate metabolism of the malaria parasites provides two targets for current antimalarials: dihydrofolate reductase and dihydropteroate synthase. Dihydrofolate reductase inhibitors have been used as antimalarials over the past few decades, often in combination with dihydropteroate synthase inhibitors. Resistance to these antifolate drugs developed through mutations in both target enzymes. However, limited mutation possibilities gave opportunities for the development of new drugs. Furthermore, other enzymes in the folate and related pathways are potential new targets that remain to be exploited. These include thymidylate synthase, an enzyme fused with dihydrofolate reductase in the same protein chain, serine hydroxymethyltransferase, methylene tetrahydrofolate dehydrogenase, methionine synthase and enzymes in the glycine cleavage pathway.
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62
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Nakanishi M, Yabe S, Tanaka N, Ito Y, Nakamura KT, Kitade Y. Mutational analyses of Plasmodium falciparum and human S-adenosylhomocysteine hydrolases. Mol Biochem Parasitol 2006; 143:146-51. [PMID: 16005528 DOI: 10.1016/j.molbiopara.2005.05.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2005] [Revised: 04/05/2005] [Accepted: 05/27/2005] [Indexed: 10/25/2022]
Abstract
S-adenosylhomocysteine hydrolase is a prospective target for developing new anti-malarial drugs. Inhibition of the hydrolase results in an anti-cellular effect due to the suppression of adenosylmethionine-dependent transmethylations. Based on the crystal structure of Plasmodium falciparum S-adenosylhomocysteine hydrolase which we have determined recently, we performed mutational analyses on P. falciparum and human enzymes. Cys59 and Ala84 of the parasite enzyme, and the equivalent residues on the human enzyme, Thr60 and Gln85, were examined. Mutations of Cys59 and Thr60 caused dramatic impact on inhibition by 2-fluoronoraristeromycin without significant effect both on its kinetic parameters and on inhibition constant against noraristeromycin. In addition, the impact was independent from the electronegativity of the side chain of the substituting residue. These results showed that steric hindrance between a functional group at the 2-position of an adenine nucleoside inhibitor and Thr60 of the human enzyme, not an electrostatic effect, contributed to inhibitor selectivity.
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Affiliation(s)
- Masayuki Nakanishi
- Department of Biomolecular Science, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
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63
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Mishra R, . BM, . NHNM. Dihydrofolate Reductase Enzyme: A Potent Target for Antimalarial Research. ACTA ACUST UNITED AC 2005. [DOI: 10.3923/ajcb.2006.48.58] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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64
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Zahouily M, Lazar M, Elmakssoudi A, Rakik J, Elaychi S, Rayadh A. QSAR for anti-malarial activity of 2-aziridinyl and 2,3-bis(aziridinyl)-1,4-naphthoquinonyl sulfonate and acylate derivatives. J Mol Model 2005; 12:398-405. [PMID: 16341716 DOI: 10.1007/s00894-005-0059-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2005] [Accepted: 07/22/2005] [Indexed: 11/28/2022]
Abstract
Quantitative structure-activity antimalarial relationships have been studied for 63 analogues of 2-aziridinyl and 2,3-bis(aziridinyl)-1,4-naphthoquinonyl sulfonate and acylate derivatives by means of multiple linear regression (MLR) and artificial neural networks (ANN). The antimalarial activity [-log(IC50x10(6))] of the compounds studied were well correlated with descriptors encoding the chemical structure. Using the pertinent descriptors revealed by a stepwise procedure in the multiple linear regression technique, a correlation coefficient of 0.9394 (s=0.2121) for the training set was obtained for the ANN model in a [3-5-1] configuration. The results show that the antimalarial activity of 2-aziridinyl and 2,3-bis(aziridinyl)-1,4-naphthoquinonyl sulfonate and acylate derivatives is strongly dependent on hydrophobic character, hydrogen-bond acceptors and also steric factors of the substituents.
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Affiliation(s)
- Mohamed Zahouily
- UFR Chimie Appliquée, Laboratoire de Catalyse, Chimiométrie et Environnement, Département de Chimie, B.P. 146, 20650, Mohammadia, Maroc.
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65
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Agarwal A, Srivastava K, Puri SK, Sinha S, Chauhan PMS. A small library of trisubstituted pyrimidines as antimalarial and antitubercular agents. Bioorg Med Chem Lett 2005; 15:5218-21. [PMID: 16171994 DOI: 10.1016/j.bmcl.2005.08.053] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2005] [Revised: 08/12/2005] [Accepted: 08/18/2005] [Indexed: 10/25/2022]
Abstract
A small library of 20 trisubstituted pyrimidines were synthesized and evaluated for their in vitro antimalarial and antitubercular activities. Out of the total screened compounds, 16 compounds have shown in vitro antimalarial activity against Plasmodium falciparum in the range of 0.25-2microg/mL and 8 compounds have shown antitubercular activity against Mycobacterium tuberculosis H(37)Ra, at a concentration of 12.5microg/mL.
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Affiliation(s)
- Anu Agarwal
- Division of Medicinal and Process Chemistry, Central Drug Research Institute, Lucknow 226001, India
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66
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Agarwal A, Srivastava K, Puri SK, Chauhan PMS. Synthesis of 4-pyrido-6-aryl-2-substituted amino pyrimidines as a new class of antimalarial agents. Bioorg Med Chem 2005; 13:6226-32. [PMID: 16054819 DOI: 10.1016/j.bmc.2005.06.052] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2005] [Revised: 06/21/2005] [Accepted: 06/22/2005] [Indexed: 10/25/2022]
Abstract
A series of 2,4,6-trisubstituted pyrimidines were synthesized and evaluated for their in vitro antimalarial activity against Plasmodium falciparum. Of the 18 compounds synthesized, 14 compounds showed MIC in the range of 0.25-2 microg/mL. These compounds are in vitro several fold more active than pyrimethamine.
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Affiliation(s)
- Anu Agarwal
- Division of Medicinal AND Process Chemistry, Central Drug Research Institute, Lucknow 226001, India
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67
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Agarwal A, Srivastava K, Puri SK, Sinha S, Chauhan PMS. Solid support synthesis of 6-aryl-2-substituted pyrimidin-4-yl phenols as anti-infective agents. Bioorg Med Chem Lett 2005; 15:4923-6. [PMID: 16169721 DOI: 10.1016/j.bmcl.2005.08.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2005] [Revised: 08/03/2005] [Accepted: 08/06/2005] [Indexed: 11/27/2022]
Abstract
A library of 30 trisubstituted pyrimidines were synthesized and evaluated for their in vitro antimalarial and antitubercular activity. Out of the 30 compounds synthesized, 23 compounds have shown in vitro antimalarial activity against Plasmodium falciparum in the range of 0.25-2 microg/mL and 16 compounds have shown antitubercular activity against Mycobacterium tuberculosis H37Ra, at a concentration of 25 microg/mL.
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Affiliation(s)
- Anu Agarwal
- Division of Medicinal & Process Chemistry, Central Drug Research Institute, Lucknow 226001, India
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68
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Mui EJ, Jacobus D, Milhous WK, Schiehser G, Hsu H, Roberts CW, Kirisits MJ, McLeod R. Triazine Inhibits Toxoplasma gondii tachyzoites in vitro and in vivo. Antimicrob Agents Chemother 2005; 49:3463-7. [PMID: 16048961 PMCID: PMC1196210 DOI: 10.1128/aac.49.8.3463-3467.2005] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The triazine WR99210 [4,6-diamino-1,2-dihydro-2,2-dimethyl-1-(2,4,5-trichlorophenoxypropyloxy)-1,3,5 triazine] inhibits Toxoplasma gondii in vitro at nanomolar levels (P < 0.05). The 50% inhibitory concentration (IC(50)) was approximately 50 nM. It is a potent inhibitor in vitro and is also effective in vivo. Administration of WR99210 parenterally (i.e., intraperitoneally) reduced the mean number of RH strain tachyzoites present in peritoneal fluid substantially 4 days after intraperitoneal infection of mice. There was a mean of approximately 35 million parasites in control mice as contrasted with approximately 2 million parasites in mice treated with 1.25 mg WR99210/kg of body weight in a representative experiment (P < 0.05). In addition the prodrug PS-15 N'-[3-(2,4, 5-trichlorophenoxy)propyloxy]-N9-(1-methylethyl) imidocarbonimidicdiamide is converted to 4,6-diamino-1,2-dihydro-2,2-dimethyl-1-(2,4,5-trichlorophenoxypropyloxy)-1,3,5 triazine in vivo when the prodrug is administered orally. PS-15 administered by gavage also reduced intraperitoneal RH strain T. gondii tachyzoite numbers. WR99210 has high efficacy and relatively low toxicity because of its substantial effect on T. gondii dihydrofolate reductase (DHFR) but not the mammalian host DHFR. Amino acid sequences of T. gondii, Plasmodium falciparum, and Homo sapiens DHFRs were compared. It is of interest that of the DHFR amino acids considered to be interacting with WR99210 in P. falciparum within interatomic distances within 3 to 5 A, four of eight were shared with T. gondii DHFR. H. sapiens also shared four amino acids thought to be interacting with WR99210. Efficacy of intraperitoneal administration of WR99210 and peroral administration of PS-15 demonstrate the potential usefulness of this class of compounds in treatment of toxoplasmosis administered either parenterally or perorally. The recent development program for this class of antimicrobials as antimalarials makes our proof of principle of improved efficacy of triazines (compared with the gold standard treatment, pyrimethamine) against T. gondii especially promising.
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Affiliation(s)
- Ernest J Mui
- The University of Chicago, 5841 S. Maryland Avenue (MC2114), AMB S-208, Chicago, IL 60637, USA
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69
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Hunt SY, Detering C, Varani G, Jacobus DP, Schiehser GA, Shieh HM, Nevchas I, Terpinski J, Sibley CH. Identification of the optimal third generation antifolate against P. falciparum and P. vivax. Mol Biochem Parasitol 2005; 144:198-205. [PMID: 16181688 DOI: 10.1016/j.molbiopara.2005.08.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2005] [Revised: 08/09/2005] [Accepted: 08/17/2005] [Indexed: 11/15/2022]
Abstract
Inhibitors of dihydrofolate reductase (DHFR) have been mainstays in the treatment of falciparum malaria. Resistance to one of these antifolates, pyrimethamine, is now common in Plasmodium falciparum populations. Antifolates have not traditionally been recommended for treatment of vivax malaria. However, recent studies have suggested that a third-generation antifolate, WR99210, is remarkably effective even against highly pyrimethamine-resistant parasites from both species. Two methods were used to identify a compound that is effective against quadruple mutant alleles from P. falciparum (N51I/C59R/S108N/I164L) and from Plasmodium vivax (57L/111L/117T/173F). The first was simple yeast system used to screen a panel of WR99210 analogs. The biguanide prodrug, JPC-2056, of the 2-chloro-4-trifluoromethoxy analog of WR99210 was effective against both the P. falciparum and P. vivax enzymes, and has been selected for further development. The second method compared the analogs in silico by docking them in the known structure of the P. falciparum DHFR-thymidylate synthase. The program reproduced well the position of the triazine ring, but the calculated energies of ligand binding were very similar for different compounds and therefore did not reproduce the observed trends in biological activity. The WR99210 family of molecules is flexible due to a long bridge between the triazine ring and the substituted benzene. During docking, multiple conformations were observed for the benzene ring part of the molecules in the DHFR active site, making computer-based predictions of binding energy less informative than for more rigid ligands. This flexibility is a key factor in their effectiveness against the highly mutant forms of DHFR.
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Affiliation(s)
- Sonia Y Hunt
- Department of Genome Sciences, University of Washington, Box 357730, Seattle, WA 98195-7730, USA
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70
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Kongsaeree P, Khongsuk P, Leartsakulpanich U, Chitnumsub P, Tarnchompoo B, Walkinshaw MD, Yuthavong Y. Crystal structure of dihydrofolate reductase from Plasmodium vivax: pyrimethamine displacement linked with mutation-induced resistance. Proc Natl Acad Sci U S A 2005; 102:13046-51. [PMID: 16135570 PMCID: PMC1201571 DOI: 10.1073/pnas.0501747102] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pyrimethamine (Pyr) targets dihydrofolate reductase of Plasmodium vivax (PvDHFR) as well as other malarial parasites, but its use as antimalarial is hampered by the widespread high resistance. Comparison of the crystal structures of PvDHFR from wild-type and the Pyr-resistant (SP21, Ser-58 --> Arg + Ser-117 --> Asn) strain as complexes with NADPH and Pyr or its analog lacking p-Cl (Pyr20) clearly shows that the steric conflict arising from the side chain of Asn-117 in the mutant enzyme, accompanied by the loss of binding to Ser-120, is mainly responsible for the reduction in binding of Pyr. Pyr20 still effectively inhibits both the wild-type and SP21 proteins, and the x-ray structures of these complexes show how Pyr20 fits into both active sites without steric strain. These structural insights suggest a general approach for developing new generations of antimalarial DHFR inhibitors that, by only occupying substrate space of the active site, would retain binding affinity with the mutant enzymes.
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Affiliation(s)
- Palangpon Kongsaeree
- Department of Chemistry and Center for Protein Structure and Function, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok 10400, Thailand
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Agarwal A, Srivastava K, Puri SK, Chauhan PMS. Synthesis of 2,4,6-trisubstituted pyrimidines as antimalarial agents. Bioorg Med Chem 2005; 13:4645-50. [PMID: 15896965 DOI: 10.1016/j.bmc.2005.04.061] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2005] [Revised: 04/21/2005] [Accepted: 04/22/2005] [Indexed: 10/25/2022]
Abstract
A series of 2,4,6-trisubstituted-pyrimidines were synthesized and evaluated for their in vitro antimalarial activity against Plasmodium falciparum. Of the 18 compounds synthesized, 14 compounds have shown MIC in the range of 0.25-2 microg/mL. These compounds are in vitro severalfold more active than pyrimethamine.
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Affiliation(s)
- Anu Agarwal
- Division of Medicinal & Process Chemistry, Central Drug Research Institute, Lucknow 226001, India
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72
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Agarwal A, Srivastava K, Puri SK, Chauhan PMS. Syntheses of 2,4,6-trisubstituted triazines as antimalarial agents. Bioorg Med Chem Lett 2005; 15:531-3. [PMID: 15664807 DOI: 10.1016/j.bmcl.2004.11.052] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2004] [Revised: 11/18/2004] [Accepted: 11/19/2004] [Indexed: 11/23/2022]
Abstract
A series of 2,4,6-trisubstituted-1,3,5-triazines (2a-s) were synthesized and evaluated for their in vitro antimalarial activity against P. falciparum. Out of the 19 compounds synthesized eight compounds showed MIC in the range of 1-2 microg/mL. These compounds are in vitro several times more active than cycloguanil.
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Affiliation(s)
- Anu Agarwal
- Division of Medicinal and Process Chemistry, Central Drug Research Institute, Lucknow 226001, India
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73
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Agarwal A, Srivastava K, Puri SK, Chauhan PMS. Antimalarial activity and synthesis of new trisubstituted pyrimidines. Bioorg Med Chem Lett 2005; 15:3130-2. [PMID: 15878272 DOI: 10.1016/j.bmcl.2005.04.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2005] [Accepted: 04/08/2005] [Indexed: 11/21/2022]
Abstract
A series of 2,4,6-trisubstituted-pyrimidines was synthesized and evaluated for their in vitro antimalarial activity against Plasmodium falciparum. Out of the 30 compounds synthesized 21 compounds showed MIC in the range of 0.5-2 microg/mL. These compounds are in vitro several folds more active than pyrimethamine.
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Affiliation(s)
- Anu Agarwal
- Division of Medicinal and Process Chemistry, Central Drug Research Institute, Lucknow 226001, India
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74
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Agarwal A, Srivastava K, Puri SK, Chauhan PMS. Synthesis of substituted indole derivatives as a new class of antimalarial agents. Bioorg Med Chem Lett 2005; 15:3133-6. [PMID: 15925306 DOI: 10.1016/j.bmcl.2005.04.011] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2005] [Revised: 04/06/2005] [Accepted: 04/08/2005] [Indexed: 11/20/2022]
Abstract
A series of substituted indole derivatives were synthesized and evaluated for their in vitro antimalarial activity against P. falciparum. Out of the 24 compounds synthesized six compounds have shown MIC of 1 microg/mL. These compounds are in vitro several folds more active than pyrimethamine.
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Affiliation(s)
- Anu Agarwal
- Division of Medicinal and Process Chemistry, Central Drug Research Institute, Lucknow 226001, India
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75
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Gregson A, Plowe CV. Mechanisms of resistance of malaria parasites to antifolates. Pharmacol Rev 2005; 57:117-45. [PMID: 15734729 DOI: 10.1124/pr.57.1.4] [Citation(s) in RCA: 309] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Antifolate antimalarial drugs interfere with folate metabolism, a pathway essential to malaria parasite survival. This class of drugs includes effective causal prophylactic and therapeutic agents, some of which act synergistically when used in combination. Unfortunately, the antifolates have proven susceptible to resistance in the malaria parasite. Resistance is caused by point mutations in dihydrofolate reductase and dihydropteroate synthase, the two key enzymes in the folate biosynthetic pathway that are targeted by the antifolates. Resistance to these drugs arises relatively rapidly in response to drug pressure and is now common worldwide. Nevertheless, antifolate drugs remain first-line agents in several sub-Saharan African countries where chloroquine resistance is widespread, at least partially because they remain the only affordable, effective alternative. New antifolate combinations that are more effective against resistant parasites are being developed and in one case, recently introduced into use. Combining these antifolates with drugs that act on different targets in the parasite should greatly enhance their effectiveness as well as deter the development of resistance. Molecular epidemiological techniques for monitoring parasite drug resistance may contribute to development of strategies for prolonging the useful therapeutic life of this important class of drugs.
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Affiliation(s)
- Aric Gregson
- Malaria Section, Center for Vaccine Development, University of Maryland School of Medicine, 685 West Baltimore Street, HSF1 Room 480, Baltimore, MD 21201, USA
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76
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Affiliation(s)
- Ivan M Kompis
- ARPIDA Ltd, Dammstrasse 36, 4142 Münchenstein, Switzerland
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77
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Waters NC, Dow GS, Kozar MP. Antimalarial compound identification and design: advances in the patent literature, 2000 – 2003. Expert Opin Ther Pat 2005. [DOI: 10.1517/13543776.14.8.1125] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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78
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Hunt SY, Rezvani BB, Sibley CH. Novel alleles of Plasmodium falciparum dhfr that confer resistance to chlorcycloguanil. Mol Biochem Parasitol 2005; 139:25-32. [PMID: 15610816 DOI: 10.1016/j.molbiopara.2004.09.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2004] [Revised: 07/13/2004] [Accepted: 09/30/2004] [Indexed: 10/26/2022]
Abstract
In Plasmodium falciparum, resistance to folate inhibitors like pyrimethamine is mediated by point mutations in the target gene dihydrofolate reductase (dhfr). The resistance to pyrimethamine increases with the accumulation of particular point mutations. These mutations also confer increased resistance to chlorcycloguanil, the active metabolite of chlorproguanil and one component of a newly introduced DHFR inhibitor, LapDap. One genotype (16V/108T) has been previously identified that confers resistance to cycloguanil but not to pyrimethamine. This study was designed to identify novel alleles that might confer resistance to chlorcycloguanil, but escape the surveillance methods currently in place for common pyrimethamine-resistant alleles. Directed mutagenesis was performed using the wild type and the common pyrimethamine-resistant allele, 51I/59R/108N, to determine the effect of the 16V and 108T mutations on enzyme activity and drug resistance. In addition, we randomly mutagenized the 51I/59R/108N allele and identified nine novel alleles that could confer resistance to chlorcycloguanil. These yeast strains were also resistant to pyrimethamine, but retained sensitivity to the experimental DHFR inhibitor, WR99210. None of the alleles generated in this study was as resistant to chlorcycloguanil as the common quadruple mutant, 51I/59R/108N/164L. In addition, selection of high levels of chlorcycloguanil resistance in parasites that carry the 51I/59R/108N allele will require two directed steps, a change from 108N to 108T followed by a mutation from A16 to 16V. The resulting allele, 16V/51I/59R/108T is highly resistant to chlorcycloguanil, but 200-fold more sensitive to pyrimethamine than the 51I/59R/108N allele.
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Affiliation(s)
- Sonia Y Hunt
- Department of Genome Sciences, University of Washington, Seattle, WA 98195-7730, USA
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79
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Gaffar FR, Wilschut K, Franssen FFJ, de Vries E. An amino acid substitution in the Babesia bovis dihydrofolate reductase-thymidylate synthase gene is correlated to cross-resistance against pyrimethamine and WR99210. Mol Biochem Parasitol 2004; 133:209-19. [PMID: 14698433 DOI: 10.1016/j.molbiopara.2003.08.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The genomic locus and cDNA encoding Babesia bovis dihydrofolate reductase-thymidylate synthase (DHFR-TS) were cloned and sequenced. A single dhfr-ts gene, composed of four exons, encodes a 511 aa protein that is most closely related to Plasmodium falciparum DHFR-TS. The genomic locus is characterized by the presence of four other genes of which at least three are expressed during the erythrocytic cycle. Three of the genes were highly conserved in closely related Theileria species and for two of the genes and dhfr-ts, gene synteny was observed between B. bovis and Theileria parva, B. bovis in vitro cultures displaying approximately 10-20-fold decreased sensitivity towards the antimalarial drugs WR99210 and pyrimethamine were selected repeatedly after prolonged growth in presence of drugs. Five cultures examined in detail were shown to encode a DHFR-TS carrying amino acid substitution S125F. Three-dimensional-modelling, using the P. falciparum DHFR structure as a template, suggests that substitution S125F protrudes into the binding site of NADPH. The S125F mutant could be isolated by growth under pyrimethamine or WR99210 pressure conferring cross-resistance to both drugs. Although opposing selection for pyrimethamine or WR99210 resistance was reported recently using P. falciparum or P. vivax strains carrying wildtype dhfr, the results obtained here are reminiscent of a quadruple mutant of P. falciparum dhfr displaying strong resistance to pyrimethamine and 10-fold enhanced resistance against WR99210. Wildtype B. bovis DHFR carries three mutations present in this mutant possibly explaining the low sensitivity to pyrimethamine and the ease by which moderately WR99210 resistant mutants could be isolated.
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Affiliation(s)
- Fasila R Gaffar
- Division of Parasitology and Tropical Veterinary Medicine, Institute of Infectious Diseases and Immunology, Utrecht University, Yalelaan 1 3584 CL Utrecht, The Netherlands
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80
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Rastelli G, Pacchioni S, Parenti MD. Structure of Plasmodium vivax dihydrofolate reductase determined by homology modeling and molecular dynamics refinement. Bioorg Med Chem Lett 2003; 13:3257-60. [PMID: 12951104 DOI: 10.1016/s0960-894x(03)00676-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The structure of Plasmodium vivax dihydrofolate reductase (PvDHFR), a potentially important target for antimalarial chemotherapy, was determined by means of homology modeling and molecular dynamics refinement. The structure proved to be consistent with DHFRs of known crystal structure. The comparison of the complexes of the antifolate inhibitor pyrimethamine bound at the active sites of PvDHFR and PfDHFR, the related enzyme from Plasmodium falciparum, prospected the possibility of using structure-based drug design to develop inhibitors that are effective against both malarial enzymes. This study constitutes a first step toward understanding of the antifolate-PvDHFR molecular interactions and possible rationalization of resistance in vivax malaria.
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Affiliation(s)
- Giulio Rastelli
- Dipartimento di Scienze Farmaceutiche, Università di Modena e Reggio Emilia, Via Campi 183, 41100 Modena, Italy.
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81
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Yuvaniyama J, Chitnumsub P, Kamchonwongpaisan S, Vanichtanankul J, Sirawaraporn W, Taylor P, Walkinshaw MD, Yuthavong Y. Insights into antifolate resistance from malarial DHFR-TS structures. Nat Struct Mol Biol 2003; 10:357-65. [PMID: 12704428 DOI: 10.1038/nsb921] [Citation(s) in RCA: 259] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2002] [Accepted: 03/25/2003] [Indexed: 01/30/2023]
Abstract
Plasmodium falciparum dihydrofolate reductase-thymidylate synthase (PfDHFR-TS) is an important target of antimalarial drugs. The efficacy of this class of DHFR-inhibitor drugs is now compromised because of mutations that prevent drug binding yet retain enzyme activity. The crystal structures of PfDHFR-TS from the wild type (TM4/8.2) and the quadruple drug-resistant mutant (V1/S) strains, in complex with a potent inhibitor WR99210, as well as the resistant double mutant (K1 CB1) with the antimalarial pyrimethamine, reveal features for overcoming resistance. In contrast to pyrimethamine, the flexible side chain of WR99210 can adopt a conformation that fits well in the active site, thereby contributing to binding. The single-chain bifunctional PfDHFR-TS has a helical insert between the DHFR and TS domains that is involved in dimerization and domain organization. Moreover, positively charged grooves on the surface of the dimer suggest a function in channeling of substrate from TS to DHFR active sites. These features provide possible approaches for the design of new drugs to overcome antifolate resistance.
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Affiliation(s)
- Jirundon Yuvaniyama
- Department of Biochemistry, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok 10400, Thailand
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82
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Birkholtz L, Joubert F, Neitz AWH, Louw AI. Comparative properties of a three-dimensional model of Plasmodium falciparum ornithine decarboxylase. Proteins 2003; 50:464-73. [PMID: 12557188 DOI: 10.1002/prot.10274] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The ornithine decarboxylase (ODC) component of the bifunctional S-adenosylmethionine decarboxylase/ornithine decarboxylase enzyme (PfAdoMetDC-ODC) of Plasmodium falciparum was modeled on the crystal structure of the Trypanosoma brucei enzyme. The homology model predicts a doughnut-shaped active homodimer that associates in a head-to-tail manner. The monomers contain two distinct domains, an N-terminal alpha/beta-barrel and a C-terminal modified Greek-key domain. These domains are structurally conserved between eukaryotic ODC enzymes and are preserved in distant analogs such as alanine racemase and triosephosphate isomerase-like proteins. Superimposition of the PfODC model on the crystal structure of the human enzyme indicates a significant degree of deviation in the carbon alpha-backbone of the solvent accessible loops. The surface locality of the ab initio modeled 38 amino acid parasite-specific insert suggests a role in the stabilization of the large bifunctional protein complex. The active site pockets of PfODC at the interface between the monomers appear to be conserved regarding the binding sites of the cofactor and substrate, but each contains five additional malaria-specific residues. The predicted PfODC homology model is consistent with mutagenesis results and biochemical studies concerning the active site residues and areas involved in stabilizing the dimeric form of the protein. Two competitive inhibitors of PfODC could be shown to interact with several parasite-specific residues in comparison with their interaction with the human ODC. The PfODC homology model contributes toward a structure-based approach for the design of novel malaria-specific inhibitors.
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Affiliation(s)
- L Birkholtz
- Department of Biochemistry, School of Biological Sciences, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, South Africa
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83
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Vilaivan T, Saesaengseerung N, Jarprung D, Kamchonwongpaisan S, Sirawaraporn W, Yuthavong Y. Synthesis of solution-phase combinatorial library of 4,6-diamino-1,2-dihydro-1,3,5-triazine and identification of new leads against A16V+S108T mutant dihydrofolate reductase of Plasmodium falciparum. Bioorg Med Chem 2003; 11:217-24. [PMID: 12470716 DOI: 10.1016/s0968-0896(02)00344-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An efficient method to synthesize solution-phase combinatorial library of 1-aryl-4,6-diamino-1,2-dihydro-1,3,5-triazine was developed. The strategy involved an acid-catalyzed cyclocondensation between arylbiguanide hydrochlorides and carbonyl compounds in the presence of triethyl orthoacetate as water scavenger. A 96-membered combinatorial library was constructed from 6 aryl biguanides and 16 carbonyl compounds. Screening of the library by iterative deconvolution method revealed two candidate leads which are equally active against wild-type Plasmodium falciparum dihydrofolate reductase, but are about 100-fold more effective against the A16V+S108T mutant enzyme as compared to cycloguanil.
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Affiliation(s)
- Tirayut Vilaivan
- Organic Synthesis Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Phayathai Road, Patumwan, Bangkok 10330, Thailand.
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84
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Wattanarangsan J, Chusacultanachai S, Yuvaniyama J, Kamchonwongpaisan S, Yuthavong Y. Effect of N-terminal truncation of Plasmodium falciparum dihydrofolate reductase on dihydrofolate reductase and thymidylate synthase activity. Mol Biochem Parasitol 2003; 126:97-102. [PMID: 12554089 DOI: 10.1016/s0166-6851(02)00240-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Jantanee Wattanarangsan
- National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Pathumthani 12120, Thailand
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85
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Hastings MD, Sibley CH. Pyrimethamine and WR99210 exert opposing selection on dihydrofolate reductase from Plasmodium vivax. Proc Natl Acad Sci U S A 2002; 99:13137-41. [PMID: 12198181 PMCID: PMC130599 DOI: 10.1073/pnas.182295999] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2002] [Indexed: 11/18/2022] Open
Abstract
Plasmodium vivax is a major public health problem in Asia and South and Central America where it is most prevalent. Until very recently, the parasite has been effectively treated with chloroquine, but resistance to this drug has now been reported in several areas. Affordable alternative treatments for vivax malaria are urgently needed. Pyrimethamine-sulfadoxine is an inhibitor of dihydrofolate reductase (DHFR) that has been widely used to treat chloroquine-resistant Plasmodium falciparum malaria. DHFR inhibitors have not been considered for treatment of vivax malaria, because initial trials showed poor efficacy against P. vivax. P. vivax cannot be grown in culture; the reason for its resistance to DHFR inhibitors is unknown. We show that, like P. falciparum, point mutations in the dhfr gene can cause resistance to pyrimethamine in P. vivax. WR99210 is a novel inhibitor of DHFR, effective even against the most pyrimethamine-resistant P. falciparum strains. We have found that it is also an extremely effective inhibitor of the P. vivax DHFR, and mutations that confer high-level resistance to pyrimethamine render the P. vivax enzyme exquisitely sensitive to WR99210. These data suggest that pyrimethamine and WR99210 would exert opposing selective forces on the P. vivax population. If used in combination, these two drugs could greatly slow the selection of parasites resistant to both drugs. If that is the case, this novel class of DHFR inhibitors could provide effective and affordable treatment for chloroquine- and pyrimethamine-resistant vivax and falciparum malaria for many years to come.
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Affiliation(s)
- Michele D Hastings
- Department of Genome Sciences, University of Washington, Box 357730, Seattle, WA 98195-7730
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86
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Delfino RT, Santos-Filho OA, Figueroa-Villar JD. Molecular modeling of wild-type and antifolate resistant mutant Plasmodium falciparum DHFR. Biophys Chem 2002; 98:287-300. [PMID: 12128181 DOI: 10.1016/s0301-4622(02)00077-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The development of drug resistance is reducing the efficiency of antifolates as antimalarials. This phenomenon has been linked to the occurrence of mutations in the parasite's dihydrofolate reductase (DHFR). In this way, the resistance to pyrimethamine and cycloguanil, two potent inhibitors of P. falciparum DHFR, is mainly related to mutations (single and crossed) at residues 16, 51, 59, 108 and 164 of the enzyme. In this work, we have refined a recently proposed homology-model of P. falciparum DHFR, and the resulting structure was used to obtain models for 14 mutant enzymes, employing molecular modeling. Ternary complexes of the mutant enzymes with these inhibitors have been superimposed to equivalent ternary complexes of the wild-type enzyme, allowing the proposition of hypotheses for the role of each mutation in drug resistance. Based on these results, possible reasons for antifolate resistance have been proposed.
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Affiliation(s)
- Reinaldo Teixeira Delfino
- Departamento de Engenharia Química, Instituto Militar de Engenharia, Praça General Tibúrcio, 80, Praia Vermelha, 22290-270, -RJ, Rio de Janeiro, Brazil
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87
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Sirawaraporn W, Sirawaraporn R, Yongkiettrakul S, Anuwatwora A, Rastelli G, Kamchonwongpaisan S, Yuthavong Y. Mutational analysis of Plasmodium falciparum dihydrofolate reductase: the role of aspartate 54 and phenylalanine 223 on catalytic activity and antifolate binding. Mol Biochem Parasitol 2002; 121:185-93. [PMID: 12034452 DOI: 10.1016/s0166-6851(02)00035-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The catalytic activity and ability to confer resistance to antifolates of Plasmodium falciparum dihydrofolate reductase (pfDHFR) through single and double mutations at Asp-54 and Phe-223 were investigated. A single Asp54Glu (D54E) mutation in the pfDHFR domain greatly decreased the catalytic activity of the enzyme and affected both the K(m) values for the substrate dihydrofolate and the K(i) values for pyrimethamine, cycloguanil and WR99210. The Phe223Ser (F223S) single mutant had unperturbed kinetics but had very poor affinity with the first two antifolates. The ability to confer high resistance to the antifolates of F223S enzyme was, however, abolished in the D54E+F223S double mutant enzyme. When D54E mutation was present together with the A16V+S108T double mutation, the effects on the K(m) values for the substrate dihydrofolate and the binding affinity of antifolates were much more pronounced. The severely impaired kinetics and poor activity observed in A16V+S108T+D54E enzyme could, however, be restored when F223S was introduced, while the binding affinities to the antifolates remained poor. The experimental findings can be explained with a model for substrate and inhibitor binding. Our data not only indicate the importance of Asp-54 of pfDHFR in catalysis and inhibitor binding, but also provide evidence that infer the potentially crucial function of the C-terminal portion of pfDHFR domain.
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Affiliation(s)
- Worachart Sirawaraporn
- Department of Biochemistry, Faculty of Science, Mahidol University, Rama 6 Rd., 10400, Bangkok 10400, Thailand.
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88
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Abstract
Resistance to antifolates of the malaria parasite Plasmodium falciparum stems from stepwise mutations of the target enzyme dihydrofolate reductase (DHFR). New drugs can be developed against resistant parasites, which are assumed to have limited possibilities in mutations. Mechanisms of resistance other than reduced binding of inhibitors to mutant enzymes may be possible and need to be further explored. New synergistic combinations of drugs targeting DHFR and dihydropteroate synthase may be employed, with new provisions against development of resistance.
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Affiliation(s)
- Yongyuth Yuthavong
- National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Rama 6 Road, 10400, Bangkok, Thailand.
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89
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Abstract
Every year there are 270 million clinical attacks of malaria and 2 million deaths, caused by the protozoan Plasmodium falciparum. Most of these cases occur in Africa. Chloroquine-resistance has led to reliance on anti-malarial antifolates, in particular the synergistic combination sulfadoxine/pyrimethamine (S/P) which targets enzymatic synthesis of folate co-factors through dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR). Resistance to S/P is now increasing and replacement antimalarials are needed. Crystal structures are not yet available for these key enzymes in the folate pathway. This review focuses on the activity of drugs on DHFR in malaria parasites, attempts to interpret differences in activity of pyrimethamine and its related drugs, and to clarify how residue changes due to point mutations determine the development of resistance. In homology-modelled P. falciparum DHFR (PfDHFR), the typical structure of four alpha-helices, 8-stranded beta-sheet, four Loops and eight Turns is clearly seen. Long polar sequences specific for Plasmodium are inserted in Turns 1 and 2. Structures immediately concerned in drug binding are beta-A, L1, alpha-B, alpha-C, T-3, beta-E, alpha-F, and beta-F. The roles of several mutations associated with resistance are discussed. In view of sequence differences in turn 3 in PfDHFR and in the human enzyme, and the marked interaction with residues of T3 of the experimental flexible antifolate WR99210 effective in pyrimethamine and cycloguanil resistance, further drug development in this area is indicated.
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Affiliation(s)
- David C Warhurst
- PHLS Malaria Laboratory, London School of Hygiene and Tropical Medicine, London WC1F 7HT.
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90
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Hankins EG, Warhurst DC, Sibley CH. Novel alleles of the Plasmodium falciparum dhfr highly resistant to pyrimethamine and chlorcycloguanil, but not WR99210. Mol Biochem Parasitol 2001; 117:91-102. [PMID: 11551635 DOI: 10.1016/s0166-6851(01)00335-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We have expressed dhfr alleles of Plasmodium falciparum in the budding yeast, Saccharomyces cerevisiae, and used this yeast model to identify single amino acid substitutions that confer high level pyrimethamine resistance on the background of the triple mutant dhfr (I51+R59+N108). Mutations in three clusters were identified: codons 50-57, 187-193, and 213-214. Several mutations previously identified in field samples were also isolated, including codons 50 and 164. The I164L mutation is of particular interest, because the quadruple mutant genotype (N51I+C59R+S108N+I164L) encodes an enzyme that is no longer inhibited by pyrimethamine, rendering sulfadoxine/pyrimethamine (SP; Fansidar) clinically ineffective. Thirty-six novel alleles were tested to determine their sensitivity to chlorcycloguanil and WR99210, two DHFR inhibitors that are in clinical and pre-clinical development, respectively. Chlorcycloguanil is effective against parasites that carry the triple mutant allele, but in vitro analysis has suggested that chlorcycloguanil will be clinically ineffective against parasites that carry the quadruple mutant allele of dhfr. In our screen, 23 of 36 novel strains were as resistant to chlorcycloguanil as the quadruple mutant, and one strain was 10-fold more resistant. WR99210 is still effective in the nM range against parasites that carry the quadruple mutant allele. In the preliminary screen, 31 of 36 novel alleles were as sensitive to WR99210 as the quadruple mutant. Detailed analysis of the remaining five showed that four of the five had IC(50) values in the same range as the quadruple mutant, and one, N51I+C59R+S108N+E192G, had an IC(50) value about fivefold higher. This result suggests that WR99210 and related compounds will be clinically effective against quadruple mutants currently found in Southeast Asia and South America and against most novel alleles that could be selected on the background of the triple mutant genotype now prevalent in East Africa.
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Affiliation(s)
- E G Hankins
- Department of Genetics, University of Washington, Seattle, WA 98195-7360, USA
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91
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Santos-Filho OA, de Alencastro RB, Figueroa-Villar JD. Homology modeling of wild type and pyrimethamine/cycloguanil-cross resistant mutant type Plasmodium falciparum dihydrofolate reductase. A model for antimalarial chemotherapy resistance. Biophys Chem 2001; 91:305-17. [PMID: 11551441 DOI: 10.1016/s0301-4622(01)00180-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We propose a low-resolution model for both the wild type and the pyrimethamine (Pyr)/cycloguanil (Cyc) cross-resistant mutant type Plasmodium falciparum DHFR (PfDHFR), based on homology modeling using chicken liver DHFR as a template. The built models contain five alpha-helices, eight beta-sheets, eight tight turns and several loops. The Ramachandran plot for the models shows 95.3 and 100% of the amino acid residues in the favorable regions for the whole enzymes and for the active sites, respectively. Furthermore, we made a preliminary analysis of the complexes Pyr/Cyc-wild DHFR and Pyr/Cyc-mutant DHFR in order to explain the probable mechanism of resistance. Our results show that the steric factor may be the main structural cause of P. falciparum resistance toward antifolate drugs.
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Affiliation(s)
- O A Santos-Filho
- Departamento de Química, Instituto Militar de Engenharia, Praça General Tibúrcio 80, Praia Vermelha 22290-270, Rio de Janeiro, Brazil
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92
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Tahar R, de Pécoulas PE, Basco LK, Chiadmi M, Mazabraud A. Kinetic properties of dihydrofolate reductase from wild-type and mutant Plasmodium vivax expressed in Escherichia coli. Mol Biochem Parasitol 2001; 113:241-9. [PMID: 11295178 DOI: 10.1016/s0166-6851(01)00230-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Antifolate drugs inhibit malarial dihydrofolate reductase (DHFR). In Plasmodium falciparum, antifolate resistance has been associated with point mutations in the gene encoding DHFR. Recently, mutations at homologous positions have been observed in the P. vivax gene. Since P. vivax cannot be propagated in a continuous in vitro culture for drug sensitivity assays, the kinetic properties of DHFR were studied by expression of the DHFR domain in Escherichia coli. Induced expression yielded a protein product that precipitated as an inclusion body in E. coli. The soluble, active DHFR recovered after denaturation and renaturation was purified to homogeneity by affinity chromatography. Kinetic properties of the recombinant P. vivax DHFR showed that the wild-type DHFR (Ser-58 and Ser-117) and double mutant DHFR (Arg-58 and Asn-117) have similar K(m) values for dihydrofolate and NADPH. Antifolate drugs (pyrimethamine, cycloguanil, trimethoprim, and methotrexate), but not proguanil (parent compound of cycloguanil) inhibit DHFR activity, as expected. The kinetics of enzyme inhibition indicated that point mutations (Ser58Arg and Ser117Asn) are associated with lower affinity between the mutant enzyme and pyrimethamine and cycloguanil, which may be the origin of antifolate resistance.
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Affiliation(s)
- R Tahar
- Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, 91198, Gif-sur-Yvette, France
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93
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Ferlan JT, Mookherjee S, Okezie IN, Fulgence L, Sibley CH. Mutagenesis of dihydrofolate reductase from Plasmodium falciparum: analysis in Saccharomyces cerevisiae of triple mutant alleles resistant to pyrimethamine or WR99210. Mol Biochem Parasitol 2001; 113:139-50. [PMID: 11254962 DOI: 10.1016/s0166-6851(01)00207-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Inhibitors of dihydrofolate reductase (DHFR) have been a mainstay of chemotherapy of falciparum malaria for >50 years. Unfortunately, point mutations in DHFR are the major cause of resistance to drugs of this class and mutations have rapidly diminished the clinical effectiveness of these drugs. We designed a simple yeast-based system to produce and analyze point mutations in the Plasmodium falciparum DHFR domain of the DHFR-thymidylate synthase gene that confers resistance to pyrimethamine (PM), the major antifolate currently used in malaria treatment, or to WR99210, an experimental antifolate. We used PCR mutagenesis, screened >1000 DHFR alleles that encoded functional enzymes and studied approximately 100 that were more resistant than a naturally occurring resistant allele (N51I and S108N). The IC(50) values for both drugs were determined for a subset of 44 alleles that carried only a single new mutation. Mutations that increased resistance to PM 10-100 fold (to >10(-4) M) were identified in three regions of the DHFR domain - around amino acids 50, 188 and 213. In contrast, mutations that caused WR-resistance were far less common and only conferred approximately 10-fold resistance (to approximately 10(-7) M). Even more interesting, only the mutations at 188 increased resistance to WR and mutations in the 213 and other regions either had no effect or actually increased sensitivity to WR. This collateral hypersensitivity raises the possibility that opposing selection for resistance/sensitivity to PM and WR might be used to slow selection of populations of P. falciparum resistant to antifolate treatment.
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Affiliation(s)
- J T Ferlan
- Department of Genetics, University of Washington, P.O. Box 357360, Seattle, WA 98195-7360, USA
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94
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Pandey SK, Naware NB, Trivedi P, Saxena AK. Molecular modeling and 3D-QSAR studies in 2-aziridinyl-and 2,3-bis(aziridinyl)-1,4-naphthoquinonyl sulfonate and acylate derivatives as potential antimalarial agents. SAR AND QSAR IN ENVIRONMENTAL RESEARCH 2001; 12:547-564. [PMID: 11813805 DOI: 10.1080/10629360108039834] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Malaria is still continuing to be one of the most dreadful diseases of the tropical countries particularly due to the development of resistance to the existing antimalarials. From observed, antimalarial activity of 2-aziridinyl- and 2,3-bis(aziridinyl)-1,4-naphthoquinonyl sulfonate and acylate derivatives acting through redox cycling mechanism, molecular modeling and three dimensional-quantitative structure activity relationship (3D-QSAR) studies have been carried out on a set of 63 compounds to identify important pharmacophors. Among several 3D-QSAR models generated, three models with correlation coefficient r > 0.82, match > 0.60 and chance = 0.00 have shown two common biophoric sites: one being the oxygen atom at position 1 of the naphthoquinone ring in terms of pi-population, charge and electron donating ability while the second being the center of the phenyl ring in terms of its 6pi-electrons. In addition to these sites, the models also share two common secondary sites: one positively contributing H-acceptor site while the second site contributing negatively in terms of steric refractivity. All these models showed good agreement between the experimental, calculated and predicted antimalarial activities.
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Affiliation(s)
- S K Pandey
- Medicinal Chemistry Division, Central Drug Research Institute, (CDRI) Chattar Manzil, Lucknow, India
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