101
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Abu Bakar N, Klonis N, Hanssen E, Chan C, Tilley L. Digestive-vacuole genesis and endocytic processes in the early intraerythrocytic stages of Plasmodium falciparum. J Cell Sci 2010; 123:441-50. [PMID: 20067995 DOI: 10.1242/jcs.061499] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The digestive vacuole of the malaria parasite Plasmodium falciparum is the site of haemoglobin digestion and haem detoxification, and is the target of chloroquine and other antimalarials. The mechanisms for genesis of the digestive vacuole and transfer of haemoglobin from the host cytoplasm are still debated. Here, we use live-cell imaging and photobleaching to monitor the uptake of the pH-sensitive fluorescent tracer SNARF-1-dextran from the erythrocyte cytoplasm in ring-stage and trophozoite-stage parasites. We compare these results with electron tomography of serial sections of parasites at different stages of growth. We show that uptake of erythrocyte cytoplasm is initiated in mid-ring-stage parasites. The host cytoplasm is internalised via cytostome-derived invaginations and concentrated into several acidified peripheral structures. Haemoglobin digestion and haemozoin formation take place in these vesicles. The ring-stage parasites can adopt a deeply invaginated cup shape but do not take up haemoglobin via macropinocytosis. As the parasite matures, the haemozoin-containing compartments coalesce to form a single acidic digestive vacuole that is fed by haemoglobin-containing vesicles. There is also evidence for haemoglobin degradation in compartments outside the digestive vacuole. The work has implications for the stage specificity of quinoline and endoperoxide antimalarials.
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102
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Egan TJ. Artemisinin-resistant Plasmodium falciparum: can the genie be put back in the bottle? Future Microbiol 2009; 4:637-9. [PMID: 19659418 DOI: 10.2217/fmb.09.42] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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103
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Abstract
Despite great international efforts, malaria still inflicts an enormous toll on human lives, especially in Africa. Throughout history, antimalarial medicines have been one of the most powerful tools in malaria control. However, the acquisition and spread of parasite strains that are resistant to multiple antimalarial drugs have become one of the greatest challenges to malaria treatment, and are associated with the increase in morbidity and mortality in many malaria-endemic countries. To deal with this grave situation, artemisinin-based combinatory therapies (ACTs) have been introduced and widely deployed in malarious regions. Artemisinin is a new class of antimalarial compounds discovered by Chinese scientists from the sweet wormwood Artemisia annua. The potential development of resistance to artemisinins by Plasmodium falciparum threatens the usable lifespan of ACTs, and therefore is a subject of close surveillance and extensive research. Studies at the Thai-Cambodian border, a historical epicenter of multidrug resistance, have detected reduced susceptibility to artemisinins as manifested by prolonged parasite-clearance times, raising considerable concerns on resistance development. Despite this significance, there is still controversy on the mode of action of artemisinins. Although a number of potential cellular targets of artemisinins have been proposed, they remain to be verified experimentally. Here, we review the history of artemisinin discovery, discuss the mode of action and potential drug targets, and present strategies to elucidate resistance mechanisms.
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Affiliation(s)
- Liwang Cui
- Department of Entomology, Pennsylvania State University, 537 ASI Building, University Park, PA 16802, USA, Tel.: +1 814 863 7663, Fax: +1 814 865 3048,
| | - Xin-zhuan Su
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA, Tel.: +1 301 402 0876, Fax: +1 301 402 2201,
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104
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Diastereoselective schenck ene reaction of singlet oxygen with chiral allylic alcohols; access to enantiomerically enriched 1,2,4-trioxanes. Tetrahedron 2009. [DOI: 10.1016/j.tet.2009.08.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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105
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106
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Kumar N, Khan SI, Beena, Rajalakshmi G, Kumaradhas P, Rawat DS. Synthesis, antimalarial activity and cytotoxicity of substituted 3,6-diphenyl-[1,2,4,5]tetraoxanes. Bioorg Med Chem 2009; 17:5632-8. [DOI: 10.1016/j.bmc.2009.06.020] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Revised: 06/04/2009] [Accepted: 06/11/2009] [Indexed: 11/29/2022]
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107
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Davies MJ, Atkinson CJ, Burns C, Woolley JG, Hipps NA, Arroo RRJ, Dungey N, Robinson T, Brown P, Flockart I, Hill C, Smith L, Bentley S. Enhancement of artemisinin concentration and yield in response to optimization of nitrogen and potassium supply to Artemisia annua. ANNALS OF BOTANY 2009; 104:315-23. [PMID: 19483202 PMCID: PMC2710909 DOI: 10.1093/aob/mcp126] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Revised: 03/23/2009] [Accepted: 04/16/2009] [Indexed: 05/14/2023]
Abstract
BACKGROUND AND AIMS The resurgence of malaria, particularly in the developing world, is considerable and exacerbated by the development of single-gene multi-drug resistances to chemicals such as chloroquinone. Drug therapies, as recommended by the World Health Organization, now include the use of antimalarial compounds derived from Artemisia annua--in particular, the use of artemisinin-based ingredients. Despite our limited knowledge of its mode of action or biosynthesis there is a need to secure a supply and enhance yields of artemisinin. The present study aims to determine how plant biomass can be enhanced while maximizing artemisinin concentration by understanding the plant's nutritional requirements for nitrogen and potassium. METHODS Experiments were carried out, the first with differing concentrations of nitrogen, at 6, 31, 56, 106, 206 or 306 mg L(-1) being applied, while the other differing in potassium concentration (51, 153 or 301 mg L(-1)). Nutrients were supplied in irrigation water to plants in pots and after a growth period biomass production and leaf artemisinin concentration were measured. These data were used to determine optimal nutrient requirements for artemisinin yield. KEY RESULTS Nitrogen nutrition enhanced plant nitrogen concentration and biomass production successively up to 106 mg N L(-1) for biomass and 206 mg N L(-1) for leaf nitrogen; further increases in nitrogen had no influence. Artemisinin concentration in dried leaf material, measured by HPLC mass spectroscopy, was maximal at a nitrogen application of 106 mg L(-1), but declined at higher concentrations. Increasing potassium application from 51 to 153 mg L(-1) increased total plant biomass, but not at higher applications. Potassium application enhanced leaf potassium concentration, but there was no effect on leaf artemisinin concentration or leaf artemisinin yield. CONCLUSIONS Artemisinin concentration declined beyond an optimal point with increasing plant nitrogen concentration. Maximization of artemisinin yield (amount per plant) requires optimization of plant biomass via control of nitrogen nutrition.
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Affiliation(s)
| | | | | | | | - Neil A. Hipps
- East Malling Research, New Road, East Malling, Kent ME19 6BJ, UK
| | | | - Nigel Dungey
- HumberVHB, Pharma Unit, Runcton Nursery, Chichester, West Sussex PO20 1LJ, UK
| | - Trevor Robinson
- Frontier, Frontier Agriculture Limited, Witham St. Hughs, Lincoln LN6 9TN, UK
| | - Paul Brown
- Frontier, Frontier Agriculture Limited, Witham St. Hughs, Lincoln LN6 9TN, UK
| | - Ian Flockart
- Botanical Developments Limited, The London Bioscience Innovation Centre, Royal College Street, London, UK
| | - Colin Hill
- Botanical Developments Limited, The London Bioscience Innovation Centre, Royal College Street, London, UK
| | - Lydia Smith
- National Institute of Agricultural Botany, Huntingdon Road, Cambridge CB3 0LE, UK
| | - Steven Bentley
- National Institute of Agricultural Botany, Huntingdon Road, Cambridge CB3 0LE, UK
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108
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Schmuck G, Klaus AM, Krötlinger F, Langewische FW. Developmental and reproductive toxicity studies on artemisone. ACTA ACUST UNITED AC 2009; 86:131-43. [PMID: 19306395 DOI: 10.1002/bdrb.20192] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND In order to justify clinical studies in women of child-bearing age with artemisone, a new artimisinin derivative, studies to assess fertility and early embryonic development in rats, developmental toxicity in rats and rabbits, and peri-post natal development in rats were performed. METHODS AND RESULTS In the study on fertility and early embryonic development (dose levels 0-5-20-80 mg/kg bw/day), doses inducing clinical and organ toxicity were used. Only in severe toxicity conditions, a reduction of the number of estruses, a prolonged time to insemination, decreased numbers of corpora lutea, implantation sites, and viable fetuses were found. Two developmental toxicity studies were performed in rats (dose levels 0-1-2 mg/kg bw/day) and rabbits (dose levels 0-2.5-5.0-7.5 mg/kg bw/day). It was shown that rats were about 5 times more sensitive than rabbits. In rats, artemisone induced total litter loss (late resorptions) at 2 mg/kg body weight and above with an increased incidence of a common vascular variation and retarded ossification at this dose. In rabbits, maternal toxicity, abortion and a slightly increased incidence of cardiac ventricular septal defects was observed at 7.5 mg/kg body weight. In a pre- and postnatal developmental toxicity study in rats (dose levels 0-1-2-4 mg/kg bw/day), 4 mg/kg body weight artemisone induced clinical symptoms and affected postnatal survival, body weight gain in the F1 pups, and motor activity. CONCLUSIONS In summary, artemisone was shown to be embryo- and fetotoxic and induced cardiac ventricular septal defects and retarded ossification in dosages where total litter loss and abortions were observed. However, no effect on reproductive and developmental parameters below severe toxic dosages could be observed.
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Affiliation(s)
- G Schmuck
- Bayer Healthcare AG, Pharma Research Center, Wuppertal, Germany.
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109
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Chollet C, Baliani A, Wong PE, Barrett MP, Gilbert IH. Targeted delivery of compounds to Trypanosoma brucei using the melamine motif. Bioorg Med Chem 2009; 17:2512-23. [PMID: 19250832 DOI: 10.1016/j.bmc.2009.01.058] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2008] [Revised: 01/21/2009] [Accepted: 01/25/2009] [Indexed: 11/29/2022]
Abstract
There is an urgent need for the development of new drugs for the treatment of human African trypanosomiasis. The causative organism, Trypanosoma brucei, has been shown to have some unusual plasma membrane transporters, in particular the P2 aminopurine transporter and related permeases, which have been used for the selective targeting of trypanocidal compounds to the organism. In this paper, we report the addition of melamine-based P2-targeting motifs to three different classes of compound in order to try and improve activity through increased selective uptake. The classes reported here are fluoroquinolones, difluoromethylornithine and artesunate derivatives.
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Affiliation(s)
- Constance Chollet
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Sir James Black Centre, Dundee DD1 5EH, UK
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110
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He SP, Tan GY, Li G, Tan WM, Nan TG, Wang BM, Li ZH, Li QX. Development of a sensitive monoclonal antibody-based enzyme-linked immunosorbent assay for the antimalaria active ingredient artemisinin in the Chinese herb Artemisia annua L. Anal Bioanal Chem 2008; 393:1297-303. [PMID: 19066864 DOI: 10.1007/s00216-008-2527-5] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Revised: 11/11/2008] [Accepted: 11/12/2008] [Indexed: 11/24/2022]
Abstract
Artemisinin is an endoperoxide sesquiterpene lactone isolated from the Chinese medicinal plant Artemisia annua L. It has been widely used in South-East Asia and Africa as an effective drug against sensitive and multidrug-resistant Plasmodium falciparum malaria. A monoclonal antibody (mAb), designated as 3H2, was generated with artesunate-bovine serum albumin conjugate as the immunogen. mAb 3H2 was used to develop a highly sensitive and specific indirect competitive enzyme-linked immunosorbent assay (icELISA) for artemisinin. The concentration of analyte producing 50% of inhibition (IC(50)) and the working range of the icELISA were 1.3 and 0.2-5.8 ng/mL, respectively. The mAb 3H2 recognized the artemisinin analogs artesunate, dihydroartemisinin, and artemether with cross-reactivity of 650%, 57%, and 3%, respectively, but negligibly recognized deoxyartemisinin and the artemisinin precursors arteannuin B and artemisinic acid. The average recoveries of artemisinin fortified in A. annua samples at concentrations from 156 to 5,000 microg/g determined by icELISA ranged from 91% to 98%. The icELISA was applied for the determination of artemisinin in different wild A. annua samples and the results were confirmed by high-performance liquid chromatography (HPLC) analysis. The correlation coefficient (R(2)) between the two assays was larger than 0.99, demonstrating a good agreement between the icELISA and HPLC results. This ELISA is suitable for quality assurance of A. annua L. materials.
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Affiliation(s)
- Su-Ping He
- College of Agronomy and Biotechnology, China Agricultural University, Beijing, 100193, China
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111
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Kumar V, Mahajan A, Chibale K. Synthetic medicinal chemistry of selected antimalarial natural products. Bioorg Med Chem 2008; 17:2236-75. [PMID: 19157883 DOI: 10.1016/j.bmc.2008.10.072] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Revised: 07/28/2008] [Accepted: 10/31/2008] [Indexed: 11/25/2022]
Abstract
Natural products remain a rich source of novel molecular scaffolds for novel antimalarial agents in the fight against malaria. This has been well demonstrated in the case of quinine and artemisinin both of which have served as templates for the development of structurally simpler analogues that either served or continue to serve as effective antimalarials. This review will expound on these two natural products as well as other selected natural products that have served either as antimalarial agents or as potential lead compounds in the development of antimalarial drugs.
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Affiliation(s)
- Vipan Kumar
- Department of Chemistry, University of Cape Town, Private Bag, Rondebosh 7701, South Africa
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112
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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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113
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De novo identification and stability of the artemisinin pharmacophore: Studies of the reductive decomposition of deoxyartemisinins and deoxyarteethers and the implications for the mode of antimalarial action. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/j.theochem.2007.08.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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114
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Haynes RK, Chan WC, Lung CM, Uhlemann AC, Eckstein U, Taramelli D, Parapini S, Monti D, Krishna S. The Fe2+-Mediated Decomposition, PfATP6 Binding, and Antimalarial Activities of Artemisone and Other Artemisinins: The Unlikelihood of C-Centered Radicals as Bioactive Intermediates. ChemMedChem 2007; 2:1480-97. [PMID: 17768732 DOI: 10.1002/cmdc.200700108] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The results of Fe(2+)-induced decomposition of the clinically used artemisinins, artemisone, other aminoartemisinins, 10-deoxoartemisinin, and the 4-fluorophenyl derivative have been compared with their antimalarial activities and their ability to inhibit the parasite SERCA PfATP6. The clinical artemisinins and artemisone decompose under aqueous conditions to give mixtures of C radical marker products, carbonyl compounds, and reduction products. The 4-fluorophenyl derivative and aminoartemisinins tend to be inert to aqueous iron(II) sulfate and anhydrous iron(II) acetate. Anhydrous iron(II) bromide enhances formation of the carbonyl compounds and provides a deoxyglycal from DHA and enamines from the aminoartemisinins. Ascorbic acid (AA) accelerates the aqueous Fe(2+)-mediated decompositions, but does not alter product distribution. 4-Oxo-TEMPO intercepts C radicals from a mixture of an antimalaria-active trioxolane, 10-deoxoartemisinin, and anhydrous iron(II) acetate to give trapped products in 73 % yield from the trioxolane, and 3 % from the artemisinin. Artemisone provides a trapped product in 10 % yield. Thus, in line with its structural rigidity, only the trioxolane provides a C radical eminently suited for intermolecular trapping. In contrast, the structural flexibility of the C radicals from the artemisinins allows facile extrusion of Fe(2+) and collapse to benign isomerization products. The propensity towards the formation of radical marker products and intermolecular radical trapping have no relationship with the in vitro antimalarial activities of the artemisinins and trioxolane. Desferrioxamine (DFO) attenuates inhibition of PfATP6 by, and antagonizes antimalarial activity of, the aqueous Fe(2+)-susceptible artemisinins, but has no overt effect on the aqueous Fe(2+)-inert artemisinins. It is concluded that the C radicals cannot be responsible for antimalarial activity and that the Fe(2+)-susceptible artemisinins may be competitively decomposed in aqueous extra- and intracellular compartments by labile Fe(2+), resulting in some attenuation of their antimalarial activities. Interpretations of the roles of DFO and AA in modulating antimalarial activities of the artemisinins, and a comparison with antimalarial properties of simple hydroperoxides and their behavior towards thapsigargin-sensitive SERCA ATPases are presented. The general basis for the exceptional antimalarial activities of artemisinins in relation to the intrinsic activity of the peroxide within the uniquely stressed environment of the malaria parasite is thereby adumbrated.
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Affiliation(s)
- Richard K Haynes
- Department of Chemistry, Open Laboratory of Chemical Biology, Institute of Molecular Technology for Drug Discovery and Synthesis, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China.
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115
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Abstract
Despite intensive research extending back to the 1930s, when the first synthetic antimalarial drugs made their appearance, the repertoire of clinically licensed formulations remains very limited. Moreover, widespread and increasing resistance to these drugs contributes enormously to the difficulties in controlling malaria, posing considerable intellectual, technical and humanitarian challenges. A detailed understanding of the molecular mechanisms underlying resistance to these agents is emerging that should permit new drugs to be rationally developed and older ones to be engineered to regain their efficacy. This review summarizes recent progress in analysing the causes of resistance to the major antimalarial drugs and its spread.
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Affiliation(s)
- John E Hyde
- Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, UK.
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116
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Stocks P, Bray P, Barton V, Al-Helal M, Jones M, Araujo N, Gibbons P, Ward S, Hughes R, Biagini G, Davies J, Amewu R, Mercer A, Ellis G, O'Neill P. Evidence for a Common Non-Heme Chelatable-Iron-Dependent Activation Mechanism for Semisynthetic and Synthetic Endoperoxide Antimalarial Drugs. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200604697] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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117
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Stocks PA, Bray PG, Barton VE, Al-Helal M, Jones M, Araujo NC, Gibbons P, Ward SA, Hughes RH, Biagini GA, Davies J, Amewu R, Mercer AE, Ellis G, O'Neill PM. Evidence for a Common Non-Heme Chelatable-Iron-Dependent Activation Mechanism for Semisynthetic and Synthetic Endoperoxide Antimalarial Drugs. Angew Chem Int Ed Engl 2007; 46:6278-83. [PMID: 17640025 DOI: 10.1002/anie.200604697] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Paul A Stocks
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
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118
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Efferth T, Li PCH, Konkimalla VSB, Kaina B. From traditional Chinese medicine to rational cancer therapy. Trends Mol Med 2007; 13:353-61. [PMID: 17644431 DOI: 10.1016/j.molmed.2007.07.001] [Citation(s) in RCA: 357] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2006] [Revised: 06/04/2007] [Accepted: 07/04/2007] [Indexed: 01/16/2023]
Abstract
Many natural products and derivatives thereof belong to the standard repertoire of cancer chemotherapy. Examples are Vinca alkaloids, taxanes and camptothecins. In recent years, the potential of natural products from plants, notably from medicinal plants used in traditional Chinese medicine (TCM), has been recognized by the scientific community in the Western world. To provide an example of the most recent developments in this field, we have selected several compounds, namely artesunate, homoharringtonine, arsenic trioxide and cantharidin, that are found in natural TCM products and that have the potential for use in cancer therapy. Controlled clinical studies have shown that homoharringtonine and arsenic trioxide can exert profound activity against leukaemia. Increased knowledge of the molecular mechanisms of TCM-derived drugs and recent developments in their applications demonstrate that the combination of TCM with modern cutting-edge technologies provides an attractive strategy for the development of novel and improved cancer therapeutics.
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Affiliation(s)
- Thomas Efferth
- German Cancer Research Center, Pharmaceutical Biology (C015), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
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119
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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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120
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Abstract
Diseases caused by tropical parasites affect hundreds of millions of people worldwide but have been largely neglected for drug development because they affect poor people in poor regions of the world. Most of the current drugs used to treat these diseases are decades old and have many limitations, including the emergence of drug resistance. This review will summarize efforts to reinvigorate the drug development pipeline for these diseases, which is driven in large part by support from major philanthropies. The organisms responsible for these diseases have a fascinating biology, and many potential biochemical targets are now apparent. These neglected diseases present unique challenges to drug development that are being addressed by new consortia of scientists from academia and industry.
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Affiliation(s)
- Adam R Renslo
- Department of Pharmaceutical Chemistry and the Small Molecule Discovery Center, University of California-San Francisco, San Francisco, CA 94158, USA
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121
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Golenser J, Waknine JH, Krugliak M, Hunt NH, Grau GE. Current perspectives on the mechanism of action of artemisinins. Int J Parasitol 2006; 36:1427-41. [PMID: 17005183 DOI: 10.1016/j.ijpara.2006.07.011] [Citation(s) in RCA: 191] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Revised: 07/24/2006] [Accepted: 07/28/2006] [Indexed: 10/24/2022]
Abstract
Artemisinin derivatives are the most recent single drugs approved and introduced for public antimalarial treatment. Although their recommended use is for treatment of Plasmodium falciparum infection, these drugs also act against other parasites, as well as against tumor cells. The mechanisms of action attributed to artemisinin include interference with parasite transport proteins, disruption of parasite mitochondrial function, modulation of host immune function and inhibition of angiogenesis. Artemisinin combination therapies are currently the preferred treatment for malaria. These combinations may prevent the induction of parasite drug resistance. However, in view of the multiple mechanisms involved, especially when additional drugs are used, the combined therapy should be carefully examined for antagonistic effects. It is now a general theory that the crucial mechanism is interference with plasmodial SERCA. Therefore, future development of resistance may be associated with overproduction or mutations of this transporter. However, a general mechanism, such as alterations in general drug transport pathways, is feasible. In this article, we review the evidence for each mechanism of action suggested.
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Affiliation(s)
- Jacob Golenser
- Department of Parasitology - The Kuvin Centre for the Study of Infectious and Tropical Diseases, The Hebrew University of Jerusalem, Jerusalem 91120, Israel.
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122
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Drew MGB, Metcalfe J, Dascombe MJ, Ismail FMD. Reactions of Artemisinin and Arteether with Acid: Implications for Stability and Mode of Antimalarial Action. J Med Chem 2006; 49:6065-73. [PMID: 17004720 DOI: 10.1021/jm060673d] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The currently accepted mechanism of trioxane antimalarial action involves generation of free radicals within or near susceptible sites probably arising from the production of distonic radical anions. An alternative mechanistic proposal involving the ionic scission of the peroxide group and consequent generation of a carbocation at C-4 has been suggested to account for antimalarial activity. We have investigated this latter mechanism using DFT (B3LYP/6-31+G* level) and established the preferred Lewis acid protonation sites (artemisinin O5a>>O4a approximately O3a>O2a>O1a; arteether O4a>or=O3a>O5b>>O2a>O1a; Figure 3) and the consequent decomposition pathways and hydrolysis sites. In neither molecule is protonation likely to occur on the peroxide bond O1-O2 and therefore lead to scission. Therefore, the alternative radical pathway remains the likeliest explanation for antimalarial action.
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Affiliation(s)
- Michael G B Drew
- Department of Chemistry, University of Reading, Reading RG6 6AD, UK
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123
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Liu C, Zhao Y, Wang Y. Artemisinin: current state and perspectives for biotechnological production of an antimalarial drug. Appl Microbiol Biotechnol 2006; 72:11-20. [PMID: 16773335 DOI: 10.1007/s00253-006-0452-0] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2006] [Revised: 03/30/2006] [Accepted: 03/30/2006] [Indexed: 10/24/2022]
Abstract
Artemisinin isolated from the aerial parts of Artemisia annua L. is a promising and potent antimalarial drug which has a remarkable activity against chloroquine-resistant and chloroquine-sensitive strains of Plasmodium falciparum, and is useful in treatment of cerebral malaria. Because the low content (0.01-1 %) of artemisinin in A. annua is a limitation to the commercial production of the drug, many research groups have been focusing their researches on enhancing the production of artemisinin in tissue culture or in the whole plant of A. annua. This review mainly focuses on the progresses made in the production of artemisinin from A. annua by biotechnological strategies including in vitro tissue culture, metabolic regulation of artemisinin biosynthesis, genetic engineering, and bioreactor technology.
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Affiliation(s)
- Chunzhao Liu
- National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100080, People's Republic of China.
- Graduate School of the Chinese Academy of Sciences, Beijing, 100049, People's Republic of China.
| | - Yan Zhao
- National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100080, People's Republic of China
- Graduate School of the Chinese Academy of Sciences, Beijing, 100049, People's Republic of China
| | - Yuchun Wang
- National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100080, People's Republic of China.
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124
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O'Neill PM. The therapeutic potential of semi-synthetic artemisinin and synthetic endoperoxide antimalarial agents. Expert Opin Investig Drugs 2006; 14:1117-28. [PMID: 16144496 DOI: 10.1517/13543784.14.9.1117] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Artemisinin derivatives such as artesunate, dihydroartemisinin and artemether are playing an increasing role in the treatment of drug-resistant malaria. They are the most potent antimalarials available, rapidly killing all asexual stages of the parasite Plasmodium falciparum. This review highlights the recent developments in the area of improved second-generation semi-synthetic artemisinin derivatives and fully synthetic antimalarial endoperoxide drugs. In pursuit of synthetic analogues of the artemisinins, one of the major challenges for chemists in this area has been the non-trivial development of techniques for the introduction of the peroxide bridge into candidate drugs. Although chemical research has enabled chemists to incorporate the endoperoxide 'warhead' into synthetic analogues of artemisinin, significant drawbacks with many candidates have included comparatively poor antimalarial activity, non-stereoselective syntheses and chemical approaches that are not readily amenable to scale up. However, very recent progress with synthetic 1,2,4-trioxolanes provides a new benchmark for future medicinal chemistry efforts in this area.
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Affiliation(s)
- Paul M O'Neill
- Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, UK.
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125
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Krishna S, Woodrow CJ, Staines HM, Haynes RK, Mercereau-Puijalon O. Re-evaluation of how artemisinins work in light of emerging evidence of in vitro resistance. Trends Mol Med 2006; 12:200-5. [PMID: 16616639 PMCID: PMC2682190 DOI: 10.1016/j.molmed.2006.03.005] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2006] [Revised: 03/02/2006] [Accepted: 03/27/2006] [Indexed: 11/18/2022]
Abstract
There are more than half a billion cases of malaria every year. Combinations of an artemisinin with other antimalarial drugs are now recommended treatments for Plasmodium falciparum malaria in most endemic areas. These treatment regimens act rapidly to relieve symptoms and effect cure. There is considerable controversy on how artemisinins work and over emerging indications of resistance to this class of antimalarial drugs. Several individual molecules have been proposed as targets for artemisinins, in addition to the idea that artemisinins might have many targets at the same time. Our suggestion that artemisinins inhibit the parasite-encoded sarco–endoplasmic reticulum Ca2+-ATPase (SERCA) PfATP6 has gained support from recent observations that a polymorphism in the gene encoding PfATP6 is associated with in vitro resistance to artemether in field isolates of P. falciparum.
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Affiliation(s)
- Sanjeev Krishna
- Centre for Infection, Division of Cellular and Molecular Medicine, St. George's, University of London SW17 0RE, UK.
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126
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O'Neill PM, Rawe SL, Borstnik K, Miller A, Ward SA, Bray PG, Davies J, Oh CH, Posner GH. Enantiomeric 1,2,4-trioxanes display equivalent in vitro antimalarial activity versus Plasmodium falciparum malaria parasites: implications for the molecular mechanism of action of the artemisinins. Chembiochem 2006; 6:2048-54. [PMID: 16222725 DOI: 10.1002/cbic.200500048] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The aim of this study was to synthesise pure enantiomers of potent antimalarial 1,2,4-trioxanes, which are related to the natural antimalarial artemisinin, and then to assay each against a panel of Plasmodium falciparum strains. The working hypothesis was that if the artemisinin derivatives interact with a specific protein-target site, then there should be stereoselective differences in their activity. In five different P. falciparum isolates, however, the trioxane enantiomers (+)-7 a, (-)-7 a and (+)-7 b, (-)-7 b, showed the same level of in vitro antiparasitic activity.
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Affiliation(s)
- Paul M O'Neill
- Department of Chemistry, University of Liverpool, The Robert Robinson Laboratories, Oxford Street, Liverpool, L69 7ZD, UK.
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127
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Hyde JE. Drug-resistant malaria. Trends Parasitol 2005; 21:494-8. [PMID: 16140578 PMCID: PMC2722032 DOI: 10.1016/j.pt.2005.08.020] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2005] [Revised: 08/08/2005] [Accepted: 08/18/2005] [Indexed: 11/26/2022]
Abstract
In the past 21 years, a modest increase in the range of antimalarial drugs approved for clinical use has been complemented by a more impressive expansion in the analysis and understanding of the molecular mechanisms underlying resistance to these agents. Such resistance is a major factor in the increasing difficulty in controlling malaria, and important developments during this period are recounted here.
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Affiliation(s)
- John E Hyde
- Faculty of Life Sciences, University of Manchester, Jackson's Mill, PO Box 88, Manchester M60 1QD, UK.
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128
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Uhlemann AC, Cameron A, Eckstein-Ludwig U, Fischbarg J, Iserovich P, Zuniga FA, East M, Lee A, Brady L, Haynes RK, Krishna S. A single amino acid residue can determine the sensitivity of SERCAs to artemisinins. Nat Struct Mol Biol 2005; 12:628-9. [PMID: 15937493 DOI: 10.1038/nsmb947] [Citation(s) in RCA: 196] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2005] [Accepted: 04/22/2005] [Indexed: 11/09/2022]
Abstract
Artemisinins are the most important class of antimalarial drugs. They specifically inhibit PfATP6, a SERCA-type ATPase of Plasmodium falciparum. Here we show that a single amino acid in transmembrane segment 3 of SERCAs can determine susceptibility to artemisinin. An L263E replacement of a malarial by a mammalian residue abolishes inhibition by artemisinins. Introducing residues found in other Plasmodium spp. also modulates artemisinin sensitivity, suggesting that artemisinins interact with the thapsigargin-binding cleft of susceptible SERCAs.
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Affiliation(s)
- Anne-Catrin Uhlemann
- Department of Cellular and Molecular Medicine, Infectious Diseases, St. George's Hospital Medical School, London SW17 0RE, UK
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129
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Abstract
Artemisinins were discovered to be highly effective antimalarial drugs shortly after the isolation of the parent artemisinin in 1971 in China. These compounds combine potent, rapid antimalarial activity with a wide therapeutic index and an absence of clinically important resistance. Artemisinin containing regimens meet the urgent need to find effective treatments for multidrug resistant malaria and have recently been advocated for widespread deployment. Comparative trials of artesunate and quinine for severe malaria are in progress to see if the persistently high mortality of this condition can be reduced.
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Affiliation(s)
- C J Woodrow
- Department of Cellular and Molecular Medicine, Infectious Diseases, St George's Hospital Medical School, Tooting, London, UK
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130
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Haynes RK, Chan HW, Ho WY, Ko CKF, Gerena L, Kyle DE, Peters W, Robinson BL. Convenient Access Both to Highly Antimalaria-Active 10-Arylaminoartemisinins, and to 10-Alkyl Ethers Including Artemether, Arteether, and Artelinate. Chembiochem 2005; 6:659-67. [PMID: 15812783 DOI: 10.1002/cbic.200400366] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
An economical phase-transfer method is used to prepare 10-arylaminoartemisinins from DHA and arylamines, and artemether, arteether, and artelinate from the corresponding alcohols. In vivo sc screens against Plasmodium berghei and P. yoelii in mice reveal that the p-fluorophenylamino derivative 5 g is some 13 and 70 times, respectively, more active than artesunate; this reflects the very high sc activity of 10-alkylaminoartemisinins. However, through the po route, the compounds are less active than the alkylaminoartemisinins, but still approximately equipotent with artesunate.
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Affiliation(s)
- Richard K Haynes
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China.
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131
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Haynes RK. Reply to Comments on ?Highly Antimalaria-Active Artemisinin Derivatives: Biological Activity Does Not Correlate with Chemical Reactivity? Angew Chem Int Ed Engl 2005. [DOI: 10.1002/anie.200462723] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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132
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Haynes RK. Reply to Comments on ?Highly Antimalaria-Active Artemisinin Derivatives: Biological Activity Does Not Correlate with Chemical Reactivity? Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200462723] [Citation(s) in RCA: 7] [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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