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Legru A, Batista FA, Puszko AK, Bouillon A, Maurel M, Martinez M, Ejjoummany A, Ortega Varga L, Adler P, Méchaly A, Hadjadj M, Sosnowski P, Hopfgartner G, Alzari PM, Blondel A, Haouz A, Barale JC, Hernandez JF. Insights from structure-activity relationships and the binding mode of peptidic α-ketoamide inhibitors of the malaria drug target subtilisin-like SUB1. Eur J Med Chem 2024; 269:116308. [PMID: 38503166 DOI: 10.1016/j.ejmech.2024.116308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 03/04/2024] [Accepted: 03/04/2024] [Indexed: 03/21/2024]
Abstract
Plasmodium multi-resistance, including against artemisinin, seriously threatens malaria treatment and control. Hence, new drugs are urgently needed, ideally targeting different parasitic stages, which are not yet targeted by current drugs. The SUB1 protease is involved in both hepatic and blood stages due to its essential role in the egress of parasites from host cells, and, as potential new target, it would meet the above criteria. We report here the synthesis as well as the biological and structural evaluation of substrate-based α-ketoamide SUB1 pseudopeptidic inhibitors encompassing positions P4-P2'. By individually substituting each position of the reference compound 1 (MAM-117, Ac-Ile-Thr-Ala-AlaCO-Asp-Glu (Oall)-NH2), we better characterized the structural determinants for SUB1 binding. We first identified compound 8 with IC50 values of 50 and 570 nM against Pv- and PfSUB1, respectively (about 3.5-fold higher potency compared to 1). Compound 8 inhibited P. falciparum merozoite egress in culture by 37% at 100 μM. By increasing the overall hydrophobicity of the compounds, we could improve the PfSUB1 inhibition level and antiparasitic activity, as shown with compound 40 (IC50 values of 12 and 10 nM against Pv- and PfSUB1, respectively, IC50 value of 23 μM on P. falciparum merozoite egress). We also found that 8 was highly selective towards SUB1 over three mammalian serine peptidases, supporting the promising value of this compound. Finally, several crystal 3D-structures of SUB1-inhibitor complexes, including with 8, were solved at high resolution to decipher the binding mode of these compounds.
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Affiliation(s)
- Alice Legru
- Institut des Biomolécules Max Mousseron (IBMM), CNRS, Univ Montpellier, ENSCM, Montpellier, France
| | - Fernando A Batista
- Structural Microbiology, UMR3528, Institut Pasteur, CNRS, Université de Paris, Paris, France
| | - Anna K Puszko
- Institut des Biomolécules Max Mousseron (IBMM), CNRS, Univ Montpellier, ENSCM, Montpellier, France
| | - Anthony Bouillon
- Structural Microbiology, UMR3528, Institut Pasteur, CNRS, Université de Paris, Paris, France
| | - Manon Maurel
- Institut des Biomolécules Max Mousseron (IBMM), CNRS, Univ Montpellier, ENSCM, Montpellier, France
| | - Mariano Martinez
- Structural Microbiology, UMR3528, Institut Pasteur, CNRS, Université de Paris, Paris, France
| | - Abdelaziz Ejjoummany
- Institut des Biomolécules Max Mousseron (IBMM), CNRS, Univ Montpellier, ENSCM, Montpellier, France
| | - Laura Ortega Varga
- Structural Bioinformatic, UMR3528, Institut Pasteur, CNRS, Université de Paris, Paris, France
| | - Pauline Adler
- Institut des Biomolécules Max Mousseron (IBMM), CNRS, Univ Montpellier, ENSCM, Montpellier, France
| | - Ariel Méchaly
- Cristallography Platform-C2RT, UMR3528, Institut Pasteur, CNRS, Université de Paris, Paris, France
| | - Margot Hadjadj
- Institut des Biomolécules Max Mousseron (IBMM), CNRS, Univ Montpellier, ENSCM, Montpellier, France
| | - Piotr Sosnowski
- Department of Inorganic and Analytical Chemistry, University of Geneva, CH-1211, Geneva, Switzerland
| | - Gérard Hopfgartner
- Department of Inorganic and Analytical Chemistry, University of Geneva, CH-1211, Geneva, Switzerland
| | - Pedro M Alzari
- Structural Microbiology, UMR3528, Institut Pasteur, CNRS, Université de Paris, Paris, France
| | - Arnaud Blondel
- Structural Bioinformatic, UMR3528, Institut Pasteur, CNRS, Université de Paris, Paris, France
| | - Ahmed Haouz
- Cristallography Platform-C2RT, UMR3528, Institut Pasteur, CNRS, Université de Paris, Paris, France
| | - Jean-Christophe Barale
- Structural Microbiology, UMR3528, Institut Pasteur, CNRS, Université de Paris, Paris, France.
| | - Jean-François Hernandez
- Institut des Biomolécules Max Mousseron (IBMM), CNRS, Univ Montpellier, ENSCM, Montpellier, France.
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van der Watt ME, Reader J, Birkholtz LM. Adapt or Die: Targeting Unique Transmission-Stage Biology for Malaria Elimination. Front Cell Infect Microbiol 2022; 12:901971. [PMID: 35755845 PMCID: PMC9218253 DOI: 10.3389/fcimb.2022.901971] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 05/06/2022] [Indexed: 12/25/2022] Open
Abstract
Plasmodium parasites have a complex life cycle that includes development in the human host as well as the Anopheles vector. Successful transmission of the parasite between its host and vector therefore requires the parasite to balance its investments in asexual replication and sexual reproduction, varying the frequency of sexual commitment to persist within the human host and generate future opportunities for transmission. The transmission window is extended further by the ability of stage V gametocytes to circulate in peripheral blood for weeks, whereas immature stage I to IV gametocytes sequester in the bone marrow and spleen until final maturation. Due to the low gametocyte numbers in blood circulation and with the ease of targeting such life cycle bottlenecks, transmission represents an efficient target for therapeutic intervention. The biological process of Plasmodium transmission is a multistage, multifaceted process and the past decade has seen a much deeper understanding of the molecular mechanisms and regulators involved. Clearly, specific and divergent processes are used during transmission compared to asexual proliferation, which both poses challenges but also opportunities for discovery of transmission-blocking antimalarials. This review therefore presents an update of our molecular understanding of gametocyte and gamete biology as well as the status of transmission-blocking activities of current antimalarials and lead development compounds. By defining the biological components associated with transmission, considerations for the development of new transmission-blocking drugs to target such untapped but unique biology is suggested as an important, main driver for transmission-blocking drug discovery.
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Affiliation(s)
- Mariëtte E van der Watt
- Institute for Sustainable Malaria Control, School of Health Systems and Public Health, University of Pretoria, Pretoria, South Africa
| | - Janette Reader
- Institute for Sustainable Malaria Control, School of Health Systems and Public Health, University of Pretoria, Pretoria, South Africa.,Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria, South Africa
| | - Lyn-Marié Birkholtz
- Institute for Sustainable Malaria Control, School of Health Systems and Public Health, University of Pretoria, Pretoria, South Africa.,Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria, South Africa
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Consalvi S, Tammaro C, Appetecchia F, Biava M, Poce G. Malaria transmission blocking compounds: a patent review. Expert Opin Ther Pat 2022; 32:649-666. [PMID: 35240899 DOI: 10.1080/13543776.2022.2049239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
INTRODUCTION Despite substantial progress in the field, malaria remains a global health issue and currently available control strategies are not sufficient to achieve eradication. Agents able to prevent transmission are likely to have a strong impact on malaria control and have been prioritized as a primary objective to reduce the number of secondary infections. Therefore, there is an increased interest in finding novel drugs targeting sexual stages of Plasmodium and innovative methods to target malaria transmission from host to vector, and vice versa. AREAS COVERED This review covers innovative transmission-blocking inventions patented between 2015 and October 2021. The focus is on chemical interventions which could be used as "chemical vaccines" to prevent transmission (small molecules, carbohydrates, and polypeptides). EXPERT OPINION Even though the development of novel strategies to block transmission still requires fundamental additional research and a deeper understanding of parasite sexual stages biology, the research in this field has significantly accelerated. Among innovative inventions patented over the last six years, the surface-delivery of antimalarial drugs to kill transmission-stages parasites in mosquitoes holds the highest promise for success in malaria control strategies, opening completely new scenarios in malaria transmission-blocking drug discovery.
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Affiliation(s)
- Sara Consalvi
- Department of Chemistry and Technologies of Drug, Sapienza University of Rome, piazzale A. Moro 5, 00185 Rome, Italy
| | - Chiara Tammaro
- Department of Chemistry and Technologies of Drug, Sapienza University of Rome, piazzale A. Moro 5, 00185 Rome, Italy
| | - Federico Appetecchia
- Department of Chemistry and Technologies of Drug, Sapienza University of Rome, piazzale A. Moro 5, 00185 Rome, Italy
| | - Mariangela Biava
- Department of Chemistry and Technologies of Drug, Sapienza University of Rome, piazzale A. Moro 5, 00185 Rome, Italy
| | - Giovanna Poce
- Department of Chemistry and Technologies of Drug, Sapienza University of Rome, piazzale A. Moro 5, 00185 Rome, Italy
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Antimalarial drug candidates in phase I and II drug development: a scoping review. Antimicrob Agents Chemother 2021; 66:e0165921. [PMID: 34843390 PMCID: PMC8846400 DOI: 10.1128/aac.01659-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The emergence and spread of parasite resistance to currently available antimalarials has highlighted the importance of developing novel antimalarials. This scoping review provides an overview of antimalarial drug candidates undergoing phase I and II studies between 1 January 2016 and 28 April 2021. PubMed, Web of Science, Embase, clinical trial registries, and reference lists were searched for relevant studies. Information regarding antimalarial compound details, clinical trial characteristics, study population, and drug pharmacokinetics and pharmacodynamics (PK-PD) were extracted. A total of 50 studies were included, of which 24 had published their results and 26 were unpublished. New antimalarial compounds were evaluated as monotherapy (28 studies, 14 drug candidates) and combination therapy (9 studies, 10 candidates). Fourteen active compounds were identified in the current antimalarial drug development pipeline together with 11 compounds that are inactive, 6 due to insufficient efficacy. PK-PD data were available from 24 studies published as open-access articles. Four unpublished studies have made their results publicly available on clinical trial registries. The terminal elimination half-life of new antimalarial compounds ranged from 14.7 to 483 h. The log10 parasite reduction ratio over 48 h and parasite clearance half-life for Plasmodium falciparum following a single-dose monotherapy were 1.55 to 4.1 and 3.4 to 9.4 h, respectively. The antimalarial drug development landscape has seen a number of novel compounds, with promising PK-PD properties, evaluated in phase I and II studies over the past 5 years. Timely public disclosure of PK-PD data is crucial for informative decision-making and drug development strategy.
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Erhunse N, Sahal D. Protecting future antimalarials from the trap of resistance: Lessons from artemisinin-based combination therapy (ACT) failures. J Pharm Anal 2021; 11:541-554. [PMID: 34765267 PMCID: PMC8572664 DOI: 10.1016/j.jpha.2020.07.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Revised: 07/19/2020] [Accepted: 07/19/2020] [Indexed: 11/01/2022] Open
Abstract
Having faced increased clinical treatment failures with dihydroartemisinin-piperaquine (DHA-PPQ), Cambodia swapped the first line artemisinin-based combination therapy (ACT) from DHA-PPQ to artesunate-mefloquine given that parasites resistant to piperaquine are susceptible to mefloquine. However, triple mutants have now emerged, suggesting that drug rotations may not be adequate to keep resistance at bay. There is, therefore, an urgent need for alternative treatment strategies to tackle resistance and prevent its spread. A proper understanding of all contributors to artemisinin resistance may help us identify novel strategies to keep artemisinins effective until new drugs become available for their replacement. This review highlights the role of the key players in artemisinin resistance, the current strategies to deal with it and suggests ways of protecting future antimalarial drugs from bowing to resistance as their predecessors did.
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Affiliation(s)
- Nekpen Erhunse
- Malaria Drug Discovery Research Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, 110067, India
- Department of Biochemistry, Faculty of Life Sciences, University of Benin, Benin City, Edo-State, Nigeria
| | - Dinkar Sahal
- Malaria Drug Discovery Research Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, 110067, India
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Duffey M, Blasco B, Burrows JN, Wells TNC, Fidock DA, Leroy D. Assessing risks of Plasmodium falciparum resistance to select next-generation antimalarials. Trends Parasitol 2021; 37:709-721. [PMID: 34001441 DOI: 10.1016/j.pt.2021.04.006] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 04/01/2021] [Accepted: 04/08/2021] [Indexed: 02/07/2023]
Abstract
Strategies to counteract or prevent emerging drug resistance are crucial for the design of next-generation antimalarials. In the past, resistant parasites were generally identified following treatment failures in patients, and compounds would have to be abandoned late in development. An early understanding of how candidate therapeutics lose efficacy as parasites evolve resistance is important to facilitate drug design and improve resistance detection and monitoring up to the postregistration phase. We describe a new strategy to assess resistance to antimalarial compounds as early as possible in preclinical development by leveraging tools to define the Plasmodium falciparum resistome, predict potential resistance risks of clinical failure for candidate therapeutics, and inform decisions to guide antimalarial drug development.
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Affiliation(s)
| | - Benjamin Blasco
- Medicines for Malaria Venture, Geneva, Switzerland; Global Antibiotic Research and Development Partnership, Geneva, Switzerland
| | | | | | - David A Fidock
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY, USA; Division of Infectious Diseases, Department of Medicine, Columbia University Irving Medical Center, New York, NY, USA
| | - Didier Leroy
- Medicines for Malaria Venture, Geneva, Switzerland.
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Moyo P, Mugumbate G, Eloff JN, Louw AI, Maharaj VJ, Birkholtz LM. Natural Products: A Potential Source of Malaria Transmission Blocking Drugs? Pharmaceuticals (Basel) 2020; 13:E251. [PMID: 32957668 PMCID: PMC7558993 DOI: 10.3390/ph13090251] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 09/15/2020] [Accepted: 09/16/2020] [Indexed: 12/17/2022] Open
Abstract
The ability to block human-to-mosquito and mosquito-to-human transmission of Plasmodium parasites is fundamental to accomplish the ambitious goal of malaria elimination. The WHO currently recommends only primaquine as a transmission-blocking drug but its use is severely restricted by toxicity in some populations. New, safe and clinically effective transmission-blocking drugs therefore need to be discovered. While natural products have been extensively investigated for the development of chemotherapeutic antimalarial agents, their potential use as transmission-blocking drugs is comparatively poorly explored. Here, we provide a comprehensive summary of the activities of natural products (and their derivatives) of plant and microbial origins against sexual stages of Plasmodium parasites and the Anopheles mosquito vector. We identify the prevailing challenges and opportunities and suggest how these can be mitigated and/or exploited in an endeavor to expedite transmission-blocking drug discovery efforts from natural products.
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Affiliation(s)
- Phanankosi Moyo
- Malaria Parasite Molecular Laboratory, Department of Biochemistry, Genetics and Microbiology, Institute for Sustainable Malaria Control, Faculty of Natural and Agricultural Sciences, University of Pretoria, Private Bag x20, Hatfield, 0028 Pretoria, South Africa;
| | - Grace Mugumbate
- Department of Chemistry, School of Natural Sciences and Mathematics, Chinhoyi University of Technology, Private Bag, 7724 Chinhoyi, Zimbabwe;
| | - Jacobus N. Eloff
- Phytomedicine Programme, Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Private Bag x04, Onderstepoort 0110 Pretoria, South Africa;
| | - Abraham I. Louw
- Malaria Parasite Molecular Laboratory, Department of Biochemistry, Genetics and Microbiology, Institute for Sustainable Malaria Control, Faculty of Natural and Agricultural Sciences, University of Pretoria, Private Bag x20, Hatfield, 0028 Pretoria, South Africa;
| | - Vinesh J. Maharaj
- Department of Chemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, Private Bag x20, Hatfield, 0028 Pretoria, South Africa;
| | - Lyn-Marié Birkholtz
- Malaria Parasite Molecular Laboratory, Department of Biochemistry, Genetics and Microbiology, Institute for Sustainable Malaria Control, Faculty of Natural and Agricultural Sciences, University of Pretoria, Private Bag x20, Hatfield, 0028 Pretoria, South Africa;
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Tainchum K, Dupont C, Chareonviriyaphap T, Jumas-Bilak E, Bangs MJ, Manguin S. Bacterial Microbiome in Wild-Caught Anopheles Mosquitoes in Western Thailand. Front Microbiol 2020; 11:965. [PMID: 32508784 PMCID: PMC7253650 DOI: 10.3389/fmicb.2020.00965] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 04/22/2020] [Indexed: 11/13/2022] Open
Abstract
Among the complex microbial community living in the mosquito midgut, some bacteria (e.g., Enterobacter spp.) can deliver effector molecules with anti-Plasmodium effects suppressing the development of malaria parasites (Plasmodium falciparum) before the öokinete can penetrate the mosquito midgut epithelium. Despite knowledge of this phenomenon, only a few studies have defined the diversity of microbiota in wild-caught adult Anopheles species. The objective of this study was to analyze and compare the bacterial microbiota in different Anopheles species, including representatives of the primary malaria vectors in western Thailand. Wild female Anopheles species were sampled from malaria-endemic areas in Tak and Mae Hong Son provinces near the Thai-Myanmar border. Midgut/abdominal bacterial diversity was assessed by examining the 16S rRNA gene, V3 hypervariable region, using PCR-Temporal Temperature Gel Electrophoresis (PCR-TTGE) profiling and sequence analysis. A total of 24 bacterial genera were identified from eight Anopheles species. Five bacterial genera were newly reported in Anopheles mosquitoes (Ferrimonas, Megasphaera, Pectobacterium, Shimwellia, and Trabulsiella). Five genera, including Megasphaera, were detected exclusively in a single-malaria (Plasmodium vivax) infected Anopheles minimus and not observed in other non-infected mosquitoes. The use of PCR-TTGE provides the first characterization of the midgut bacterial microbiome present in wild adult Anopheles in Thailand. Evidence that microbiota might impact pathogen development (suppression) in Anopheles and thereby reduce the risk of pathogen transmission deserves more studies to describe the presence and better understand the biological role of bacteria in natural mosquito populations.
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Affiliation(s)
- Krajana Tainchum
- Agricultural Innovation and Management Division, Faculty of Natural Resources, Prince of Songkla University, Songkhla, Thailand
- Center for Advanced Studies for Agriculture and Food, KU Institute for Advanced Studies, Kasetsart University, Bangkok, Thailand
| | - Chloé Dupont
- HydroSciences Montpellier, Institut de Recherche pour le Développement, CNRS, Université Montpellier, Montpellier, France
- Centre Hospitalier Universitaire, Laboratoire d’Hygiène Hospitalière, Montpellier, France
| | - Theeraphap Chareonviriyaphap
- Center for Advanced Studies for Agriculture and Food, KU Institute for Advanced Studies, Kasetsart University, Bangkok, Thailand
| | - Estelle Jumas-Bilak
- HydroSciences Montpellier, Institut de Recherche pour le Développement, CNRS, Université Montpellier, Montpellier, France
- Centre Hospitalier Universitaire, Laboratoire d’Hygiène Hospitalière, Montpellier, France
| | - Michael J. Bangs
- Center for Advanced Studies for Agriculture and Food, KU Institute for Advanced Studies, Kasetsart University, Bangkok, Thailand
- Public Health & Malaria Control, PT Freeport Indonesia/International SOS, Kuala Kencana, Indonesia
| | - Sylvie Manguin
- HydroSciences Montpellier, Institut de Recherche pour le Développement, CNRS, Université Montpellier, Montpellier, France
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Abstract
Currently, nitazoxanide is the only FDA-approved treatment for cryptosporidiosis; unfortunately, it is ineffective in immunocompromised patients, has varied efficacy in immunocompetent individuals, and is not approved in infants under 1 year of age. Identifying new inhibitors for the treatment of cryptosporidiosis requires standardized and quantifiable in vitro assays for assessing potency, selectivity, timing of activity, and reversibility. Here, we provide new protocols for defining which stages of the life cycle are susceptible to four highly active compound classes that likely inhibit different targets in the parasite. We also utilize a newly developed long-term culture system to define assays for monitoring reversibility as a means of defining cidal activity as a function of concentration and time of treatment. These assays should provide valuable in vitro parameters to establish conditions for efficacious in vivo treatment. Cryptosporidium parvum and Cryptosporidium hominis have emerged as major enteric pathogens of infants in the developing world, in addition to their known importance in immunocompromised adults. Although there has been recent progress in identifying new small molecules that inhibit Cryptosporidium sp. growth in vitro or in animal models, we lack information about their mechanism of action, potency across the life cycle, and cidal versus static activities. Here, we explored four potent classes of compounds that include inhibitors that likely target phosphatidylinositol 4 kinase (PI4K), phenylalanine-tRNA synthetase (PheRS), and several potent inhibitors with unknown mechanisms of action. We utilized monoclonal antibodies and gene expression probes for staging life cycle development to define the timing of when inhibitors were active during the life cycle of Cryptosporidium parvum grown in vitro. These different classes of inhibitors targeted different stages of the life cycle, including compounds that blocked replication (PheRS inhibitors), prevented the segmentation of daughter cells and thus blocked egress (PI4K inhibitors), or affected sexual-stage development (a piperazine compound of unknown mechanism). Long-term cultivation of C. parvum in epithelial cell monolayers derived from intestinal stem cells was used to distinguish between cidal and static activities based on the ability of parasites to recover from treatment. Collectively, these approaches should aid in identifying mechanisms of action and for designing in vivo efficacy studies based on time-dependent concentrations needed to achieve cidal activity.
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Norcross NR, Wilson C, Baragaña B, Hallyburton I, Osuna‐Cabello M, Norval S, Riley J, Fletcher D, Sinden R, Delves M, Ruecker A, Duffy S, Meister S, Antonova‐Koch Y, Crespo B, de Cózar C, Sanz LM, Gamo FJ, Avery VM, Frearson JA, Gray DW, Fairlamb AH, Winzeler EA, Waterson D, Campbell SF, Willis PA, Read KD, Gilbert IH. Substituted Aminoacetamides as Novel Leads for Malaria Treatment. ChemMedChem 2019; 14:1329-1335. [PMID: 31188540 PMCID: PMC6899483 DOI: 10.1002/cmdc.201900329] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Indexed: 01/29/2023]
Abstract
Herein we describe the optimization of a phenotypic hit against Plasmodium falciparum based on an aminoacetamide scaffold. This led to N-(3-chloro-4-fluorophenyl)-2-methyl-2-{[4-methyl-3-(morpholinosulfonyl)phenyl]amino}propanamide (compound 28) with low-nanomolar activity against the intraerythrocytic stages of the malaria parasite, and which was found to be inactive in a mammalian cell counter-screen up to 25 μm. Inhibition of gametes in the dual gamete activation assay suggests that this family of compounds may also have transmission blocking capabilities. Whilst we were unable to optimize the aqueous solubility and microsomal stability to a point at which the aminoacetamides would be suitable for in vivo pharmacokinetic and efficacy studies, compound 28 displayed excellent antimalarial potency and selectivity; it could therefore serve as a suitable chemical tool for drug target identification.
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Affiliation(s)
- Neil R. Norcross
- Drug Discovery UnitDivision of Biological Chemistry and Drug DiscoverySchool of Life SciencesUniversity of DundeeDundeeDD1 5EHUK
| | - Caroline Wilson
- Drug Discovery UnitDivision of Biological Chemistry and Drug DiscoverySchool of Life SciencesUniversity of DundeeDundeeDD1 5EHUK
| | - Beatriz Baragaña
- Drug Discovery UnitDivision of Biological Chemistry and Drug DiscoverySchool of Life SciencesUniversity of DundeeDundeeDD1 5EHUK
| | - Irene Hallyburton
- Drug Discovery UnitDivision of Biological Chemistry and Drug DiscoverySchool of Life SciencesUniversity of DundeeDundeeDD1 5EHUK
| | - Maria Osuna‐Cabello
- Drug Discovery UnitDivision of Biological Chemistry and Drug DiscoverySchool of Life SciencesUniversity of DundeeDundeeDD1 5EHUK
| | - Suzanne Norval
- Drug Discovery UnitDivision of Biological Chemistry and Drug DiscoverySchool of Life SciencesUniversity of DundeeDundeeDD1 5EHUK
| | - Jennifer Riley
- Drug Discovery UnitDivision of Biological Chemistry and Drug DiscoverySchool of Life SciencesUniversity of DundeeDundeeDD1 5EHUK
| | - Daniel Fletcher
- Drug Discovery UnitDivision of Biological Chemistry and Drug DiscoverySchool of Life SciencesUniversity of DundeeDundeeDD1 5EHUK
| | | | | | | | - Sandra Duffy
- Discovery BiologyGriffith Institute for Drug DiscoveryGriffith UniversityNathanQueensland4111Australia
| | - Stephan Meister
- Department of PediatricsUniversity of California San Diego School of Medicine9500 Gilman Drive 0741La JollaCA92093USA
| | - Yevgeniya Antonova‐Koch
- Department of PediatricsUniversity of California San Diego School of Medicine9500 Gilman Drive 0741La JollaCA92093USA
| | - Benigno Crespo
- GlaxoSmithKline, Diseases of the Developing World – Tres Cantos Medicines Development Campusc/ Severo Ochoa 2, Tres Cantos28760MadridSpain
| | - Cristina de Cózar
- GlaxoSmithKline, Diseases of the Developing World – Tres Cantos Medicines Development Campusc/ Severo Ochoa 2, Tres Cantos28760MadridSpain
| | - Laura M. Sanz
- GlaxoSmithKline, Diseases of the Developing World – Tres Cantos Medicines Development Campusc/ Severo Ochoa 2, Tres Cantos28760MadridSpain
| | - Francisco Javier Gamo
- GlaxoSmithKline, Diseases of the Developing World – Tres Cantos Medicines Development Campusc/ Severo Ochoa 2, Tres Cantos28760MadridSpain
| | - Vicky M. Avery
- Discovery BiologyGriffith Institute for Drug DiscoveryGriffith UniversityNathanQueensland4111Australia
| | - Julie A. Frearson
- Drug Discovery UnitDivision of Biological Chemistry and Drug DiscoverySchool of Life SciencesUniversity of DundeeDundeeDD1 5EHUK
| | - David W. Gray
- Drug Discovery UnitDivision of Biological Chemistry and Drug DiscoverySchool of Life SciencesUniversity of DundeeDundeeDD1 5EHUK
| | - Alan H. Fairlamb
- Drug Discovery UnitDivision of Biological Chemistry and Drug DiscoverySchool of Life SciencesUniversity of DundeeDundeeDD1 5EHUK
| | - Elizabeth A. Winzeler
- Department of PediatricsUniversity of California San Diego School of Medicine9500 Gilman Drive 0741La JollaCA92093USA
| | - David Waterson
- Medicines for Malaria VentureInternational Centre, Cointrin, Entrance G, 3rd FloorRoute de Pré-Bois 20, PO Box 1826Geneva1215Switzerland
| | - Simon F. Campbell
- Medicines for Malaria VentureInternational Centre, Cointrin, Entrance G, 3rd FloorRoute de Pré-Bois 20, PO Box 1826Geneva1215Switzerland
| | - Paul A. Willis
- Medicines for Malaria VentureInternational Centre, Cointrin, Entrance G, 3rd FloorRoute de Pré-Bois 20, PO Box 1826Geneva1215Switzerland
| | - Kevin D. Read
- Drug Discovery UnitDivision of Biological Chemistry and Drug DiscoverySchool of Life SciencesUniversity of DundeeDundeeDD1 5EHUK
| | - Ian H. Gilbert
- Drug Discovery UnitDivision of Biological Chemistry and Drug DiscoverySchool of Life SciencesUniversity of DundeeDundeeDD1 5EHUK
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van der Watt ME, Reader J, Churchyard A, Nondaba SH, Lauterbach SB, Niemand J, Abayomi S, van Biljon RA, Connacher JI, van Wyk RDJ, Le Manach C, Paquet T, González Cabrera D, Brunschwig C, Theron A, Lozano-Arias S, Rodrigues JFI, Herreros E, Leroy D, Duffy J, Street LJ, Chibale K, Mancama D, Coetzer TL, Birkholtz LM. Potent Plasmodium falciparum gametocytocidal compounds identified by exploring the kinase inhibitor chemical space for dual active antimalarials. J Antimicrob Chemother 2019; 73:1279-1290. [PMID: 29420756 DOI: 10.1093/jac/dky008] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 01/02/2018] [Indexed: 01/06/2023] Open
Abstract
Objectives Novel chemical tools to eliminate malaria should ideally target both the asexual parasites and transmissible gametocytes. Several imidazopyridazines (IMPs) and 2-aminopyridines (2-APs) have been described as potent antimalarial candidates targeting lipid kinases. However, these have not been extensively explored for stage-specific inhibition of gametocytes in Plasmodium falciparum parasites. Here we provide an in-depth evaluation of the gametocytocidal activity of compounds from these chemotypes and identify novel starting points for dual-acting antimalarials. Methods We evaluated compounds against P. falciparum gametocytes using several assay platforms for cross-validation and stringently identified hits that were further profiled for stage specificity, speed of action and ex vivo efficacy. Physicochemical feature extraction and chemogenomic fingerprinting were applied to explore the kinase inhibition susceptibility profile. Results We identified 34 compounds with submicromolar activity against late stage gametocytes, validated across several assay platforms. Of these, 12 were potent at <100 nM (8 were IMPs and 4 were 2-APs) and were also active against early stage gametocytes and asexual parasites, with >1000-fold selectivity towards the parasite over mammalian cells. Front-runner compounds targeted mature gametocytes within 48 h and blocked transmission to mosquitoes. The resultant chemogenomic fingerprint of parasites treated with the lead compounds revealed the importance of targeting kinases in asexual parasites and gametocytes. Conclusions This study encompasses an in-depth evaluation of the kinase inhibitor space for gametocytocidal activity. Potent lead compounds have enticing dual activities and highlight the importance of targeting the kinase superfamily in malaria elimination strategies.
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Affiliation(s)
- Mariëtte E van der Watt
- Department of Biochemistry, Institute for Sustainable Malaria Control and South African Medical Research Council Collaborating Centre for Malaria Research, University of Pretoria, Private Bag x20, Hatfield, Pretoria 0028, South Africa
| | - Janette Reader
- Department of Biochemistry, Institute for Sustainable Malaria Control and South African Medical Research Council Collaborating Centre for Malaria Research, University of Pretoria, Private Bag x20, Hatfield, Pretoria 0028, South Africa
| | - Alisje Churchyard
- Plasmodium Molecular Research Unit, Wits Research Institute for Malaria, Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and National Health Laboratory Service, Johannesburg 2193, South Africa
| | - Sindisiwe H Nondaba
- Department of Biochemistry, Institute for Sustainable Malaria Control and South African Medical Research Council Collaborating Centre for Malaria Research, University of Pretoria, Private Bag x20, Hatfield, Pretoria 0028, South Africa
| | - Sonja B Lauterbach
- Plasmodium Molecular Research Unit, Wits Research Institute for Malaria, Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and National Health Laboratory Service, Johannesburg 2193, South Africa
| | - Jandeli Niemand
- Department of Biochemistry, Institute for Sustainable Malaria Control and South African Medical Research Council Collaborating Centre for Malaria Research, University of Pretoria, Private Bag x20, Hatfield, Pretoria 0028, South Africa
| | - Sijuade Abayomi
- Department of Biochemistry, Institute for Sustainable Malaria Control and South African Medical Research Council Collaborating Centre for Malaria Research, University of Pretoria, Private Bag x20, Hatfield, Pretoria 0028, South Africa
| | - Riëtte A van Biljon
- Department of Biochemistry, Institute for Sustainable Malaria Control and South African Medical Research Council Collaborating Centre for Malaria Research, University of Pretoria, Private Bag x20, Hatfield, Pretoria 0028, South Africa
| | - Jessica I Connacher
- Department of Biochemistry, Institute for Sustainable Malaria Control and South African Medical Research Council Collaborating Centre for Malaria Research, University of Pretoria, Private Bag x20, Hatfield, Pretoria 0028, South Africa
| | - Roelof D J van Wyk
- Department of Biochemistry, Institute for Sustainable Malaria Control and South African Medical Research Council Collaborating Centre for Malaria Research, University of Pretoria, Private Bag x20, Hatfield, Pretoria 0028, South Africa
| | - Claire Le Manach
- Drug Discovery and Development Centre (H3D), Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - Tanya Paquet
- Drug Discovery and Development Centre (H3D), Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - Diego González Cabrera
- Drug Discovery and Development Centre (H3D), Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - Christel Brunschwig
- Drug Discovery and Development Centre (H3D), Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - Anjo Theron
- Biosciences, Council for Scientific and Industrial Research, PO Box 395, Pretoria 0001, South Africa
| | - Sonia Lozano-Arias
- GlaxoSmithKline, Tres Cantos Medicines Development Campus, Severo Ochoa, 2, 28760 Tres Cantos, Madrid, Spain
| | - Janneth F I Rodrigues
- GlaxoSmithKline, Tres Cantos Medicines Development Campus, Severo Ochoa, 2, 28760 Tres Cantos, Madrid, Spain
| | - Esperanza Herreros
- GlaxoSmithKline, Tres Cantos Medicines Development Campus, Severo Ochoa, 2, 28760 Tres Cantos, Madrid, Spain
| | - Didier Leroy
- Medicines for Malaria Venture, International Center Cointrin, Route de Pré-Bois 20, 1215, Geneva, Switzerland
| | - James Duffy
- Medicines for Malaria Venture, International Center Cointrin, Route de Pré-Bois 20, 1215, Geneva, Switzerland
| | - Leslie J Street
- Drug Discovery and Development Centre (H3D), Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa
| | - Kelly Chibale
- Drug Discovery and Development Centre (H3D), Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa.,South African Medical Research Council, Drug Discovery and Development Research Unit, Department of Chemistry and Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Rondebosch 7701, South Africa
| | - Dalu Mancama
- Biosciences, Council for Scientific and Industrial Research, PO Box 395, Pretoria 0001, South Africa
| | - Theresa L Coetzer
- Plasmodium Molecular Research Unit, Wits Research Institute for Malaria, Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and National Health Laboratory Service, Johannesburg 2193, South Africa
| | - Lyn-Marie Birkholtz
- Department of Biochemistry, Institute for Sustainable Malaria Control and South African Medical Research Council Collaborating Centre for Malaria Research, University of Pretoria, Private Bag x20, Hatfield, Pretoria 0028, South Africa
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12
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Yahiya S, Rueda-Zubiaurre A, Delves MJ, Fuchter MJ, Baum J. The antimalarial screening landscape-looking beyond the asexual blood stage. Curr Opin Chem Biol 2019; 50:1-9. [PMID: 30875617 PMCID: PMC6591700 DOI: 10.1016/j.cbpa.2019.01.029] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 01/28/2019] [Accepted: 01/30/2019] [Indexed: 12/20/2022]
Abstract
In recent years, the research agenda to tackle global morbidity and mortality from malaria disease has shifted towards innovation, in the hope that efforts at the frontiers of scientific research may re-invigorate gains made towards eradication. Discovery of new antimalarial drugs with novel chemotypes or modes of action lie at the heart of these efforts. There is a particular interest in drug candidates that target stages of the malaria parasite lifecycle beyond the symptomatic asexual blood stages. This is especially important given the spectre of emerging drug resistance to all current frontline antimalarials. One approach gaining increased interest is the potential of designing novel drugs that target parasite passage from infected individual to feeding mosquito and back again. Action of such therapeutics is geared much more at the population level rather than just concerned with the infected individual. The search for novel drugs active against these stages has been helped by improvements to in vitro culture of transmission and pre-erythrocytic parasite lifecycle stages, robotic automation and high content imaging, methodologies that permit the high-throughput screening (HTS) of compound libraries for drug discovery. Here, we review recent advances in the antimalarial screening landscape, focussed on transmission blocking as a key aim for drug-treatment campaigns of the future.
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Affiliation(s)
- Sabrina Yahiya
- Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, South Kensington, London SW7 2AZ, UK
| | - Ainoa Rueda-Zubiaurre
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London W12 OBZ, UK
| | - Michael J Delves
- London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Matthew J Fuchter
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London W12 OBZ, UK
| | - Jake Baum
- Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, South Kensington, London SW7 2AZ, UK.
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13
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Orjuela-Sanchez P, Villa ZH, Moreno M, Tong-Rios C, Meister S, LaMonte GM, Campo B, Vinetz JM, Winzeler EA. Developing Plasmodium vivax Resources for Liver Stage Study in the Peruvian Amazon Region. ACS Infect Dis 2018. [PMID: 29542317 DOI: 10.1021/acsinfecdis.7b00198] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
To develop new drugs and vaccines for malaria elimination, it will be necessary to discover biological interventions, including small molecules that act against Plasmodium vivax exoerythrocytic forms. However, a robust in vitro culture system for P. vivax is still lacking. Thus, to study exoerythrocytic forms, researchers must have simultaneous access to fresh, temperature-controlled patient blood samples, as well as an anopheline mosquito colony. In addition, researchers must rely on native mosquito species to avoid introducing a potentially dangerous invasive species into a malaria-endemic region. Here, we report an in vitro culture system carried out on site in a malaria-endemic region for liver stage parasites of P. vivax sporozoites obtained from An. darlingi, the main malaria vector in the Americas. P. vivax sporozoites were obtained by dissection of salivary glands from infected An. darlingi mosquitoes and purified by Accudenz density gradient centrifugation. HC04 liver cells were exposed to P. vivax sporozoites and cultured up to 9 days. To overcome low P. vivax patient parasitemias, potentially lower mosquito vectorial capacity, and humid, nonsterile environmental conditions, a new antibiotic cocktail was included in tissue culture to prevent contamination. Culturing conditions supported exoerythrocytic (EEF) P. vivax liver stage growth up to 9 days and allowed for maturation into intrahepatocyte merosomes. Some of the identified small forms were resistant to atovaquone (1 μM) but sensitive to the phosphatidylinositol 4-kinase inhibitor, KDU691 (1 μM). This study reports a field-accessible EEF production process for drug discovery in a malaria-endemic site in which viable P. vivax sporozoites are used for drug studies using hepatocyte infection. Our data demonstrate that the development of meaningful, field-based resources for P. vivax liver stage drug screening and liver stage human malaria experimentation in the Amazon region is feasible.
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Affiliation(s)
- Pamela Orjuela-Sanchez
- Division of Host-Microbe Systems and Therapeutics, Health Sciences Center for Immunology, Infection and Inflammation, Department of Pediatrics, School of Medicine, University of California, San Diego, 9500 Gilman Drive #0760, La Jolla, California 92093-0760, United States
| | - Zaira Hellen Villa
- Laboratorio ICEMR-Amazonia, Laboratorios de Investigacion y Desarrollo, Facultad de Ciencias y Filosofia, Universidad Peruana Cayetano Heredia, Av. Honorio Delgado 430, San Martín de Porres, Lima, 15102, Peru
| | - Marta Moreno
- Division of Infectious Diseases, Department of Medicine, University of California, San Diego, 9500 Gilman Drive #0760, La Jolla, California 92093-0760, United States
| | - Carlos Tong-Rios
- Laboratorio ICEMR-Amazonia, Laboratorios de Investigacion y Desarrollo, Facultad de Ciencias y Filosofia, Universidad Peruana Cayetano Heredia, Av. Honorio Delgado 430, San Martín de Porres, Lima, 15102, Peru
| | - Stephan Meister
- Division of Host-Microbe Systems and Therapeutics, Health Sciences Center for Immunology, Infection and Inflammation, Department of Pediatrics, School of Medicine, University of California, San Diego, 9500 Gilman Drive #0760, La Jolla, California 92093-0760, United States
| | - Gregory M. LaMonte
- Division of Host-Microbe Systems and Therapeutics, Health Sciences Center for Immunology, Infection and Inflammation, Department of Pediatrics, School of Medicine, University of California, San Diego, 9500 Gilman Drive #0760, La Jolla, California 92093-0760, United States
| | - Brice Campo
- Medicines for Malaria Venture (MMV), International Center Cointrin, Block G, 20 Route de Pre-Bois, POB 1826, Geneva, CH-1215, Switzerland
| | - Joseph M. Vinetz
- Laboratorio ICEMR-Amazonia, Laboratorios de Investigacion y Desarrollo, Facultad de Ciencias y Filosofia, Universidad Peruana Cayetano Heredia, Av. Honorio Delgado 430, San Martín de Porres, Lima, 15102, Peru
- Division of Infectious Diseases, Department of Medicine, University of California, San Diego, 9500 Gilman Drive #0760, La Jolla, California 92093-0760, United States
- Instituto de Medicina Tropical “Alexander von Humboldt”, Universidad Peruana Cayetano Heredia, Lima, 15102, Peru
| | - Elizabeth A. Winzeler
- Division of Host-Microbe Systems and Therapeutics, Health Sciences Center for Immunology, Infection and Inflammation, Department of Pediatrics, School of Medicine, University of California, San Diego, 9500 Gilman Drive #0760, La Jolla, California 92093-0760, United States
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14
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Buskes MJ, Harvey KL, Richards BJ, Kalhor R, Christoff RM, Gardhi CK, Littler DR, Cope ED, Prinz B, Weiss GE, O'Brien NJ, Crabb BS, Deady LW, Gilson PR, Abbott BM. Antimalarial activity of novel 4-cyano-3-methylisoquinoline inhibitors against Plasmodium falciparum: design, synthesis and biological evaluation. Org Biomol Chem 2018; 14:4617-39. [PMID: 27105169 DOI: 10.1039/c5ob02517f] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Central to malaria pathogenesis is the invasion of human red blood cells by Plasmodium falciparum parasites. Following each cycle of intracellular development and replication, parasites activate a cellular program to egress from their current host cell and invade a new one. The orchestration of this process critically relies upon numerous organised phospho-signaling cascades, which are mediated by a number of central kinases. Parasite kinases are emerging as novel antimalarial targets as they have diverged sufficiently from their mammalian counterparts to allow selectable therapeutic action. Parasite protein kinase A (PfPKA) is highly expressed late in the cell cycle of the parasite blood stage and has been shown to phosphorylate a critical invasion protein, Apical Membrane Antigen 1. This enzyme could therefore be a valuable drug target so we have repurposed a substituted 4-cyano-3-methylisoquinoline that has been shown to inhibit rat PKA with the goal of targeting PfPKA. We synthesised a novel series of compounds and, although many potently inhibit the growth of chloroquine sensitive and resistant strains of P. falciparum, they were found to have minimal activity against PfPKA, indicating that they likely have another target important to parasite cytokinesis and invasion.
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Affiliation(s)
- Melissa J Buskes
- Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
| | - Katherine L Harvey
- Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria 3004, Australia and Department of Microbiology and Immunology, Peter Doherty Institute, University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Benjamin J Richards
- Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
| | - Robabeh Kalhor
- Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
| | - Rebecca M Christoff
- Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
| | - Chamodi K Gardhi
- Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
| | | | - Elliott D Cope
- Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria 3004, Australia
| | - Boris Prinz
- Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria 3004, Australia
| | - Greta E Weiss
- Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria 3004, Australia
| | - Nathan J O'Brien
- Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
| | - Brendan S Crabb
- Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria 3004, Australia and Department of Microbiology and Immunology, Peter Doherty Institute, University of Melbourne, Melbourne, Victoria 3010, Australia and Monash University, Melbourne, Victoria 3800, Australia
| | - Leslie W Deady
- Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
| | - Paul R Gilson
- Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria 3004, Australia and Monash University, Melbourne, Victoria 3800, Australia
| | - Belinda M Abbott
- Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
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15
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Li H, Sun W, Huang X, Lu X, Patel PR, Kim M, Orr MJ, Fisher RM, Tanaka TQ, McKew JC, Simeonov A, Sanderson PE, Zheng W, Williamson KC, Huang W. Efficient Synthesis of 1,9-Substituted Benzo[h][1,6]naphthyridin-2(1H)-ones and Evaluation of their Plasmodium falciparum Gametocytocidal Activities. ACS COMBINATORIAL SCIENCE 2017; 19:748-754. [PMID: 29024590 DOI: 10.1021/acscombsci.7b00119] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A novel three-component, two-step, one-pot nucleophilic aromatic substitution (SNAr)-intramolecular cyclization-Suzuki coupling reaction was developed for the synthesis of benzo[h][1,6]naphthyridin-2(1H)-ones (Torins). On the basis of the new efficiently convergent synthetic route, a library of Torin analogs was synthesized. The antimalarial activities of these compounds were evaluated against asexual parasites using a growth inhibition assay and gametocytes using a viability assay.
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Affiliation(s)
- Hao Li
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Wei Sun
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Xiuli Huang
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Xiao Lu
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Paresma R. Patel
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Myunghoon Kim
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Meghan J. Orr
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Richard M. Fisher
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Takeshi Q Tanaka
- Laboratory
of Malaria and Vector Research, National Institute of Allergy and
Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - John C. McKew
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Anton Simeonov
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Philip E. Sanderson
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Wei Zheng
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Kim C. Williamson
- Department
of Biology, Loyola University Chicago, Chicago, Illinois 60660, United States
- Microbiology
and Immunology Department, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, Maryland 20814, United States
| | - Wenwei Huang
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
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16
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Ullah I, Sharma R, Biagini GA, Horrocks P. A validated bioluminescence-based assay for the rapid determination of the initial rate of kill for discovery antimalarials. J Antimicrob Chemother 2017; 72:717-726. [PMID: 27999014 DOI: 10.1093/jac/dkw449] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 09/22/2016] [Indexed: 11/13/2022] Open
Abstract
Objectives A future treatment for uncomplicated malaria will contain at least one component that exerts a rapid rate of kill. We describe here the validation and application of a simple, robust and rapid bioluminescence-based assay for the determination of the initial rate of kill in intra-erythrocytic asexual stages of Plasmodium falciparum . Methods A modification to the concentration-response bioluminescence [here termed bioluminescence relative rate of kill (BRRoK)] assay, utilizing exposure to fold-IC 50 concentrations (0.33× to 9×), was used to monitor the immediate cytocidal effect of 372 open-source compounds for antimalarial drug discovery available through the Medicines for Malaria Venture Malaria Box. Results Antimalarial drugs that exert a rapid cytocidal effect produce a concentration-dependent loss of bioluminescence signal that correlates with available in vitro and in vivo estimates of parasite clearance time and parasite reduction ratio. Following the measurement of IC 50 for the Malaria Box compounds in Dd2 luc , the BRRoK assay was used to identify and rank 372 compounds for their initial cytocidal activity. Fifty-three compounds in the Malaria Box show an initial relative rate of kill greater than that of chloroquine, with 17 of these having an initial relative rate of kill greater than that of dihydroartemisinin. Conclusions The BRRoK assay provides a rapid assay format for the estimation of a key pharmacodynamic property of antimalarial drug action. The simplicity and robustness of the assay suggests it would be readily scalable for high-throughput screening and a critical decision-making tool for antimalarial drug development.
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Affiliation(s)
- Imran Ullah
- Institute for Science and Technology in Medicine, Keele University, Staffordshire ST5 5BG, UK
| | - Raman Sharma
- Research Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Giancarlo A Biagini
- Research Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Paul Horrocks
- Institute for Science and Technology in Medicine, Keele University, Staffordshire ST5 5BG, UK
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17
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Bounaadja L, Schmitt M, Albrecht S, Mouray E, Tarnus C, Florent I. Selective inhibition of PfA-M1, over PfA-M17, by an amino-benzosuberone derivative blocks malaria parasites development in vitro and in vivo. Malar J 2017; 16:382. [PMID: 28934959 PMCID: PMC5609037 DOI: 10.1186/s12936-017-2032-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 09/18/2017] [Indexed: 01/09/2023] Open
Abstract
Background Plasmodium falciparum M1 family aminopeptidase is currently considered as a promising target for anti-malarial chemotherapy. Several series of inhibitors developed by various research groups display IC50/Ki values down to nM range on native PfA-M1 or recombinant forms and block the parasite development in culture at µM to sub-µM concentrations. A handful of these inhibitors has been tested on murine models of malaria and has shown anti plasmodial in vivo activity. However, most of these inhibitors do also target the other neutral malarial aminopeptidase, PfA-M17, often with lower Ki values, which questions the relative involvement and importance of each enzyme in the parasite biology. Results An amino-benzosuberone derivative from a previously published collection of chemicals targeting specifically the M1-aminopeptidases has been identified; it is highly potent on PfA-M1 (Ki = 50 nM) and devoid of inhibitory activity on PfA-M17 (no inhibition up to 100 µM). This amino-benzosuberone derivative (T5) inhibits, in the µM range, the in vitro growth of two P. falciparum strains, 3D7 and FcB1, respectively chloroquino-sensitive and resistant. Evaluated in vivo, on the murine non-lethal model of malaria Plasmodium chabaudi chabaudi, this amino-benzosuberone derivative was able to reduce the parasite burden by 44 and 40% in a typical 4-day Peters assay at a daily dose of 12 and 24 mg/kg by intraperitoneal route of administration. Conclusions The evaluation of a highly selective inhibitor of PfA-M1, over PfA-M17, active on Plasmodium parasites in vitro and in vivo, highlights the relevance of PfA-M1 in the biological development of the parasite as well as in the list of promising anti-malarial targets to be considered in combination with current or future anti-malarial drugs. Electronic supplementary material The online version of this article (doi:10.1186/s12936-017-2032-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Lotfi Bounaadja
- Molécules de Communication et Adaptation des Microorganismes, (MCAM, UMR7245), Muséum National Histoire Naturelle, Sorbonne Universités, CNRS, CP 52, 57 Rue Cuvier, 75005, Paris, France
| | - Marjorie Schmitt
- Laboratoire de Chimie Moléculaire, CNRS-UMR7509, Université de Strasbourg, 67037, Strasbourg Cedex 2, France
| | - Sébastien Albrecht
- Laboratoire de Chimie Organique et Bioorganique, EA4566, Université de Haute Alsace, 68093, Mulhouse Cedex, France
| | - Elisabeth Mouray
- Molécules de Communication et Adaptation des Microorganismes, (MCAM, UMR7245), Muséum National Histoire Naturelle, Sorbonne Universités, CNRS, CP 52, 57 Rue Cuvier, 75005, Paris, France
| | - Céline Tarnus
- Laboratoire de Chimie Organique et Bioorganique, EA4566, Université de Haute Alsace, 68093, Mulhouse Cedex, France
| | - Isabelle Florent
- Molécules de Communication et Adaptation des Microorganismes, (MCAM, UMR7245), Muséum National Histoire Naturelle, Sorbonne Universités, CNRS, CP 52, 57 Rue Cuvier, 75005, Paris, France.
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18
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Bretscher MT, Griffin JT, Ghani AC, Okell LC. Modelling the benefits of long-acting or transmission-blocking drugs for reducing Plasmodium falciparum transmission by case management or by mass treatment. Malar J 2017; 16:341. [PMID: 28814310 PMCID: PMC5559805 DOI: 10.1186/s12936-017-1988-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 08/09/2017] [Indexed: 11/16/2022] Open
Abstract
Background Anti-malarial drugs are an important tool for malaria control and elimination. Alongside their direct benefit in the treatment of disease, drug use has a community-level effect, clearing the reservoir of infection and reducing onward transmission of the parasite. Different compounds potentially have different impacts on transmission—with some providing periods of prolonged chemoprophylaxis whilst others have greater transmission-blocking potential. The aim was to quantify the relative benefit of such properties for transmission reduction to inform target product profiles in the drug development process and choice of first-line anti-malarial treatment in different endemic settings. Methods A mathematical model of Plasmodium falciparum epidemiology was used to estimate the transmission reduction that can be achieved by using drugs of varying chemoprophylactic (protection for 3, 30 or 60 days) or transmission-blocking activity (blocking 79, 92 or 100% of total onward transmission). Simulations were conducted at low, medium or high transmission intensity (slide-prevalence in 2–10 year olds being 1, 10 or 40%, respectively), with drugs administered either via case management or mass drug administration (MDA). Results Transmission reductions depend strongly on deployment strategy, treatment coverage and endemicity level. Transmission-blocking was most effective at low endemicity, whereas chemoprophylaxis was most useful at high endemicity levels. Increasing the duration of protection as much as possible was beneficial. Increasing transmission-blocking activity from the level of ACT to a 100% transmission-blocking drug (close to the effect estimated for ACT combined with primaquine) produced moderate impact but was not as effective as increasing the duration of protection in medium-to-high transmission settings (slide prevalence 10–40%). Combining both good transmission-blocking activity (e.g. as achieved by ACT or ACT + primaquine) and a long duration of protection (30 days or more, such as provided by piperaquine or mefloquine) within a drug regimen can substantially increase impact compared with drug regimens with only one of these properties in medium to high transmission areas (slide-prevalence in 2–10 year olds ~10 to 40%). These results applied whether the anti-malarials were used for case management or for MDA. Discussion These results emphasise the importance of increasing access to treatment for routine case management, and the potential value of choosing first-line anti-malarial treatment policies according to local malaria epidemiology to maximise impact on transmission. There is no indication that the optimal drug choice should differ between delivery via case management or MDA. Electronic supplementary material The online version of this article (doi:10.1186/s12936-017-1988-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Michael T Bretscher
- Department of Infectious Disease Epidemiology, MRC Centre for Outbreak Analysis & Modelling, Imperial College, London, UK.,F. Hoffmann-La Roche Ltd, Basel, Switzerland
| | - Jamie T Griffin
- School of Mathematical Sciences, Queen Mary University of London, London, UK
| | - Azra C Ghani
- Department of Infectious Disease Epidemiology, MRC Centre for Outbreak Analysis & Modelling, Imperial College, London, UK
| | - Lucy C Okell
- Department of Infectious Disease Epidemiology, MRC Centre for Outbreak Analysis & Modelling, Imperial College, London, UK.
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Abdulah R, Suradji EW, Subarnas A, Supratman U, Sugijanto M, Diantini A, Lestari K, Barliana MI, Kawazu S, Koyama H. Catechin Isolated from Garcinia celebica Leaves Inhibit Plasmodium falciparum Growth through the Induction of Oxidative Stress. Pharmacogn Mag 2017; 13:S301-S305. [PMID: 28808396 PMCID: PMC5538170 DOI: 10.4103/pm.pm_571_16] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2016] [Revised: 02/01/2017] [Indexed: 11/04/2022] Open
Abstract
BACKGROUND Resistance of antimalarial drugs to Plasmodium falciparum has become a major concern in malaria eradication. Although it is also affected by several socioeconomic factors, a new antiplasmodial agent is needed for a global malaria control program. OBJECTIVE In this study, we attempted to uncover the antiplasmodial properties of Garcinia celebica, an Indonesian medicinal plant, along with the responsible compound and its possible mechanism. MATERIALS AND METHODS The G. celebica leaves were ethanol extracted and fractionated based on their polarity using n-hexane, ethyl acetate, and water. The antiplasmodial activity was tested in vitro against chloroquine-resistant P. falciparum at 100 μg/ml for 72 h. The active compound of the most active ethyl acetate fraction was subsequently isolated using column chromatography and identified by nuclear magnetic resonance. RESULTS The IC50 of (+)-catechin, the characterized compound, against P. falciparum was 198 μM in 24 h and experiment. The isolated catechin inhibited P. falciparum growth in both trophozoite and schizont stages. An additional experiment also suggests that the antiplasmodial property of catechin occurs through the induction of the oxidative stress to P. falciparum. CONCLUSION This result shows that the potential of catechin and its antimalarial properties should be explored further. SUMMARY Garcinia celebica leaf extract and fractions inhibit Plasmodium falciparum growthCatechin, the active compound of Garcinia celebica leaf extract, inhibits Plasmodium falciparum growth in a time- and dose-dependent manner Abbreviations used: RBC: Red Blood Cells; IC50: Inhibition Concentrattino 50; MeOH: Methanol; RPMI: Roswell Park Memorial Institute; EI: Electron Ionization.
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Affiliation(s)
- Rizky Abdulah
- Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Universitas Padjadjaran, Jatinangor 45363, Indonesia.,Department of Public Health, Gunma University Graduate School of Medicine, Maebashi 371-8511, Japan
| | - Eka W Suradji
- Department of Public Health, Gunma University Graduate School of Medicine, Maebashi 371-8511, Japan.,Teluk Bintuni Hospital, Teluk Bintuni Regency, West Papua 98364, Indonesia
| | - Anas Subarnas
- Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Universitas Padjadjaran, Jatinangor 45363, Indonesia
| | - Unang Supratman
- Department of Chemistry, Faculty of Mathematics and Natural Science, Universitas Padjadjaran, Jatinangor 45363, Indonesia
| | - Milyadi Sugijanto
- Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Universitas Padjadjaran, Jatinangor 45363, Indonesia
| | - Ajeng Diantini
- Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Universitas Padjadjaran, Jatinangor 45363, Indonesia
| | - Keri Lestari
- Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy, Universitas Padjadjaran, Jatinangor 45363, Indonesia
| | - Melisa I Barliana
- Department of Biological Pharmacy, Faculty of Pharmacy, Universitas Padjadjaran, Jatinangor 45363, Indonesia
| | - Shinichiro Kawazu
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada, Obihiro, Japan
| | - Hiroshi Koyama
- Department of Public Health, Gunma University Graduate School of Medicine, Maebashi 371-8511, Japan
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20
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Burrows JN, Duparc S, Gutteridge WE, Hooft van Huijsduijnen R, Kaszubska W, Macintyre F, Mazzuri S, Möhrle JJ, Wells TNC. New developments in anti-malarial target candidate and product profiles. Malar J 2017; 16:26. [PMID: 28086874 PMCID: PMC5237200 DOI: 10.1186/s12936-016-1675-x] [Citation(s) in RCA: 297] [Impact Index Per Article: 42.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 12/30/2016] [Indexed: 11/10/2022] Open
Abstract
A decade of discovery and development of new anti-malarial medicines has led to a renewed focus on malaria elimination and eradication. Changes in the way new anti-malarial drugs are discovered and developed have led to a dramatic increase in the number and diversity of new molecules presently in pre-clinical and early clinical development. The twin challenges faced can be summarized by multi-drug resistant malaria from the Greater Mekong Sub-region, and the need to provide simplified medicines. This review lists changes in anti-malarial target candidate and target product profiles over the last 4 years. As well as new medicines to treat disease and prevent transmission, there has been increased focus on the longer term goal of finding new medicines for chemoprotection, potentially with long-acting molecules, or parenteral formulations. Other gaps in the malaria armamentarium, such as drugs to treat severe malaria and endectocides (that kill mosquitoes which feed on people who have taken the drug), are defined here. Ultimately the elimination of malaria requires medicines that are safe and well-tolerated to be used in vulnerable populations: in pregnancy, especially the first trimester, and in those suffering from malnutrition or co-infection with other pathogens. These updates reflect the maturing of an understanding of the key challenges in producing the next generation of medicines to control, eliminate and ultimately eradicate malaria.
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Affiliation(s)
- Jeremy N Burrows
- Medicines for Malaria Venture, Route de Pré Bois 20, 1215, Geneva 15, Switzerland
| | - Stephan Duparc
- Medicines for Malaria Venture, Route de Pré Bois 20, 1215, Geneva 15, Switzerland
| | | | | | - Wiweka Kaszubska
- Medicines for Malaria Venture, Route de Pré Bois 20, 1215, Geneva 15, Switzerland
| | - Fiona Macintyre
- Medicines for Malaria Venture, Route de Pré Bois 20, 1215, Geneva 15, Switzerland
| | | | - Jörg J Möhrle
- Medicines for Malaria Venture, Route de Pré Bois 20, 1215, Geneva 15, Switzerland
| | - Timothy N C Wells
- Medicines for Malaria Venture, Route de Pré Bois 20, 1215, Geneva 15, Switzerland.
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21
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Le Bihan A, de Kanter R, Angulo-Barturen I, Binkert C, Boss C, Brun R, Brunner R, Buchmann S, Burrows J, Dechering KJ, Delves M, Ewerling S, Ferrer S, Fischli C, Gamo–Benito FJ, Gnädig NF, Heidmann B, Jiménez-Díaz MB, Leroy D, Martínez MS, Meyer S, Moehrle JJ, Ng CL, Noviyanti R, Ruecker A, Sanz LM, Sauerwein RW, Scheurer C, Schleiferboeck S, Sinden R, Snyder C, Straimer J, Wirjanata G, Marfurt J, Price RN, Weller T, Fischli W, Fidock DA, Clozel M, Wittlin S. Characterization of Novel Antimalarial Compound ACT-451840: Preclinical Assessment of Activity and Dose-Efficacy Modeling. PLoS Med 2016; 13:e1002138. [PMID: 27701420 PMCID: PMC5049785 DOI: 10.1371/journal.pmed.1002138] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 08/24/2016] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Artemisinin resistance observed in Southeast Asia threatens the continued use of artemisinin-based combination therapy in endemic countries. Additionally, the diversity of chemical mode of action in the global portfolio of marketed antimalarials is extremely limited. Addressing the urgent need for the development of new antimalarials, a chemical class of potent antimalarial compounds with a novel mode of action was recently identified. Herein, the preclinical characterization of one of these compounds, ACT-451840, conducted in partnership with academic and industrial groups is presented. METHOD AND FINDINGS The properties of ACT-451840 are described, including its spectrum of activities against multiple life cycle stages of the human malaria parasite Plasmodium falciparum (asexual and sexual) and Plasmodium vivax (asexual) as well as oral in vivo efficacies in two murine malaria models that permit infection with the human and the rodent parasites P. falciparum and Plasmodium berghei, respectively. In vitro, ACT-451840 showed a 50% inhibition concentration of 0.4 nM (standard deviation [SD]: ± 0.0 nM) against the drug-sensitive P. falciparum NF54 strain. The 90% effective doses in the in vivo efficacy models were 3.7 mg/kg against P. falciparum (95% confidence interval: 3.3-4.9 mg/kg) and 13 mg/kg against P. berghei (95% confidence interval: 11-16 mg/kg). ACT-451840 potently prevented male gamete formation from the gametocyte stage with a 50% inhibition concentration of 5.89 nM (SD: ± 1.80 nM) and dose-dependently blocked oocyst development in the mosquito with a 50% inhibitory concentration of 30 nM (range: 23-39). The compound's preclinical safety profile is presented and is in line with the published results of the first-in-man study in healthy male participants, in whom ACT-451840 was well tolerated. Pharmacokinetic/pharmacodynamic (PK/PD) modeling was applied using efficacy in the murine models (defined either as antimalarial activity or as survival) in relation to area under the concentration versus time curve (AUC), maximum observed plasma concentration (Cmax), and time above a threshold concentration. The determination of the dose-efficacy relationship of ACT-451840 under curative conditions in rodent malaria models allowed prediction of the human efficacious exposure. CONCLUSION The dual activity of ACT-451840 against asexual and sexual stages of P. falciparum and the activity on P. vivax have the potential to meet the specific profile of a target compound that could replace the fast-acting artemisinin component and harbor additional gametocytocidal activity and, thereby, transmission-blocking properties. The fast parasite reduction ratio (PRR) and gametocytocidal effect of ACT-451840 were recently also confirmed in a clinical proof-of-concept (POC) study.
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Affiliation(s)
| | | | - Iñigo Angulo-Barturen
- GlaxoSmithKline, TresCantos Medicines Development Campus, Diseases of the Developing World, Tres Cantos, Madrid, Spain
| | | | | | - Reto Brun
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Ralf Brunner
- Actelion Pharmaceuticals Ltd, Allschwil, Switzerland
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | | | | | | | - Michael Delves
- Department of Life Sciences, Imperial College London, SW7 2AZ, London, United Kingdom
| | | | - Santiago Ferrer
- GlaxoSmithKline, TresCantos Medicines Development Campus, Diseases of the Developing World, Tres Cantos, Madrid, Spain
| | - Christoph Fischli
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Francisco Javier Gamo–Benito
- GlaxoSmithKline, TresCantos Medicines Development Campus, Diseases of the Developing World, Tres Cantos, Madrid, Spain
| | - Nina F. Gnädig
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, New York, United States of America
| | | | - María Belén Jiménez-Díaz
- GlaxoSmithKline, TresCantos Medicines Development Campus, Diseases of the Developing World, Tres Cantos, Madrid, Spain
| | - Didier Leroy
- Medicines for Malaria Venture, Geneva, Switzerland
| | - Maria Santos Martínez
- GlaxoSmithKline, TresCantos Medicines Development Campus, Diseases of the Developing World, Tres Cantos, Madrid, Spain
| | - Solange Meyer
- Actelion Pharmaceuticals Ltd, Allschwil, Switzerland
| | | | - Caroline L. Ng
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, New York, United States of America
| | | | - Andrea Ruecker
- Department of Life Sciences, Imperial College London, SW7 2AZ, London, United Kingdom
| | - Laura María Sanz
- GlaxoSmithKline, TresCantos Medicines Development Campus, Diseases of the Developing World, Tres Cantos, Madrid, Spain
| | | | - Christian Scheurer
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Sarah Schleiferboeck
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Robert Sinden
- Department of Life Sciences, Imperial College London, SW7 2AZ, London, United Kingdom
| | | | - Judith Straimer
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, New York, United States of America
| | - Grennady Wirjanata
- Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, Australia
| | - Jutta Marfurt
- Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, Australia
| | - Ric N. Price
- Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, Australia
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom
| | - Thomas Weller
- Actelion Pharmaceuticals Ltd, Allschwil, Switzerland
| | | | - David A. Fidock
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, New York, United States of America
- Division of Infectious Diseases, Department of Medicine, Columbia University Medical Center, New York, New York, United States of America
| | | | - Sergio Wittlin
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- * E-mail:
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22
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Buskes MJ, Harvey KL, Prinz B, Crabb BS, Gilson PR, Wilson DJD, Abbott BM. Exploration of 3-methylisoquinoline-4-carbonitriles as protein kinase A inhibitors of Plasmodium falciparum. Bioorg Med Chem 2016; 24:2389-2396. [PMID: 27112453 DOI: 10.1016/j.bmc.2016.03.048] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 03/16/2016] [Accepted: 03/27/2016] [Indexed: 11/29/2022]
Abstract
A series of isoquinolines have been evaluated in a homology model of Plasmodium falciparum Protein Kinase A (PfPKA) using molecular dynamics. Synthesis of these compounds was then undertaken to investigate their structure-activity relationships. One compound was found to inhibit parasite growth in an in vitro assay and provides a lead to further develop 3-methylisoquinoline-4-carbonitriles as antimalarial compounds. Development of a potent and selective PfPKA inhibitor would provide a useful tool to shed further insight into the mechanisms enabling malaria parasites to establish infection.
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Affiliation(s)
- Melissa J Buskes
- Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia
| | - Katherine L Harvey
- Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria 3004, Australia
| | - Boris Prinz
- Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria 3004, Australia
| | - Brendan S Crabb
- Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria 3004, Australia; Monash University, Melbourne, Victoria 3800, Australia; University of Melbourne, Melbourne 3010, Australia
| | - Paul R Gilson
- Centre for Biomedical Research, Burnet Institute, Melbourne, Victoria 3004, Australia; Monash University, Melbourne, Victoria 3800, Australia
| | - David J D Wilson
- Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia
| | - Belinda M Abbott
- Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia.
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Birkholtz LM, Coetzer TL, Mancama D, Leroy D, Alano P. Discovering New Transmission-Blocking Antimalarial Compounds: Challenges and Opportunities. Trends Parasitol 2016; 32:669-681. [PMID: 27209388 DOI: 10.1016/j.pt.2016.04.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 04/24/2016] [Accepted: 04/26/2016] [Indexed: 01/08/2023]
Abstract
The ability to target human-mosquito parasite transmission challenges global malaria elimination. However, it is not obvious what a transmission-blocking drug will look like; should it target only parasite transmission stages; be combined with a partner drug killing the pathogenic asexual stages; or kill both the sexual and asexual blood stages, preferably displaying polypharmacology? The development of transmission-blocking antimalarials requires objective analyses of the current strategies. Here, pertinent issues and questions regarding the target candidate profile of a transmission-blocking compound, and its role in malaria elimination strategies, are highlighted and novel perspectives proposed. The essential role of a test cascade that integrates screening and validation strategies to identify next-generation transmission-blocking antimalarials is emphasised.
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Affiliation(s)
- Lyn-Marie Birkholtz
- Department of Biochemistry, Centre for Sustainable Malaria Control, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, South Africa.
| | - Theresa L Coetzer
- Department of Molecular Medicine and Haematology, Wits Research Institute for Malaria, Faculty of Health Sciences, University of the Witwatersrand, National Health Laboratory Service, Johannesburg, South Africa.
| | - Dalu Mancama
- Department of Biochemistry, Centre for Sustainable Malaria Control, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, South Africa; Biosciences, Council for Scientific and Industrial Research, Pretoria, South Africa.
| | - Didier Leroy
- Medicines for Malaria Venture, Geneva, Switzerland.
| | - Pietro Alano
- Dipartimento di Malattie Infettive, Parassitarie e Immunomediate, Istituto Superiore di Sanità, Rome, Italy.
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Luciferase-Based, High-Throughput Assay for Screening and Profiling Transmission-Blocking Compounds against Plasmodium falciparum Gametocytes. Antimicrob Agents Chemother 2016; 60:2097-107. [PMID: 26787698 DOI: 10.1128/aac.01949-15] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2015] [Accepted: 01/11/2016] [Indexed: 01/11/2023] Open
Abstract
The discovery of new antimalarial drugs able to target both the asexual and gametocyte stages ofPlasmodium falciparumis critical to the success of the malaria eradication campaign. We have developed and validated a robust, rapid, and cost-effective high-throughput reporter gene assay to identify compounds active against late-stage (stage IV and V) gametocytes. The assay, which is suitable for testing compound activity at incubation times up to 72 h, demonstrates excellent quality and reproducibility, with averageZ' values of 0.85 ± 0.01. We used the assay to screen more than 10,000 compounds from three chemically diverse libraries. The screening outcomes highlighted the opportunity to use collections of compounds with known activity against the asexual stages of the parasites as a starting point for gametocytocidal activity detection in order to maximize the chances of identifying gametocytocidal compounds. This assay extends the capabilities of our previously reported luciferase assay, which tested compounds against early-stage gametocytes, and opens possibilities to profile the activities of gametocytocidal compounds over the entire course of gametocytogenesis.
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Verlinden BK, Louw A, Birkholtz LM. Resisting resistance: is there a solution for malaria? Expert Opin Drug Discov 2016; 11:395-406. [PMID: 26926843 DOI: 10.1517/17460441.2016.1154037] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
INTRODUCTION Currently, widely used antimalarial drugs have a limited clinical lifespan due to parasite resistance development. With resistance continuously rising, antimalarial drug discovery requires strategies to decrease the time of delivering a new antimalarial drug while simultaneously increasing the drug's therapeutic lifespan. Lessons learnt from various chemotherapeutic resistance studies in the fields of antibiotic and cancer research offer potentially useful strategies that can be applied to antimalarial drug discovery. AREAS COVERED In this review the authors discuss current strategies to circumvent resistance in malaria and alternatives that could be employed. EXPERT OPINION Scientists have been 'beating back' the malaria parasite with novel drugs for the past 49 years but the constant rise in antimalarial drug resistance is forcing the drug discovery community to explore alternative strategies. Avant-garde anti-resistance strategies from alternative fields may assist our endeavors to manage, control and prevent antimalarial drug resistance to progress beyond beating the resistant parasite back, to stopping it dead in its tracks.
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Affiliation(s)
- Bianca K Verlinden
- a Department of Biochemistry, Centre for Sustainable Malaria Control, Faculty of Natural and Agricultural Sciences , University of Pretoria , Pretoria , South Africa
| | - Abraham Louw
- a Department of Biochemistry, Centre for Sustainable Malaria Control, Faculty of Natural and Agricultural Sciences , University of Pretoria , Pretoria , South Africa
| | - Lyn-Marié Birkholtz
- a Department of Biochemistry, Centre for Sustainable Malaria Control, Faculty of Natural and Agricultural Sciences , University of Pretoria , Pretoria , South Africa
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26
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Challenges in Antimalarial Drug Treatment for Vivax Malaria Control. Trends Mol Med 2015; 21:776-788. [DOI: 10.1016/j.molmed.2015.10.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2015] [Revised: 10/19/2015] [Accepted: 10/20/2015] [Indexed: 01/01/2023]
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Spillman NJ, Kirk K. The malaria parasite cation ATPase PfATP4 and its role in the mechanism of action of a new arsenal of antimalarial drugs. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2015; 5:149-62. [PMID: 26401486 PMCID: PMC4559606 DOI: 10.1016/j.ijpddr.2015.07.001] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Revised: 07/03/2015] [Accepted: 07/08/2015] [Indexed: 11/28/2022]
Abstract
The intraerythrocytic malaria parasite, Plasmodium falciparum, maintains a low cytosolic Na(+) concentration and the plasma membrane P-type cation translocating ATPase 'PfATP4' has been implicated as playing a key role in this process. PfATP4 has been the subject of significant attention in recent years as mutations in this protein confer resistance to a growing number of new antimalarial compounds, including the spiroindolones, the pyrazoles, the dihydroisoquinolones, and a number of the antimalarial agents in the Medicines for Malaria Venture's 'Malaria Box'. On exposure of parasites to these compounds there is a rapid disruption of cytosolic Na(+). Whether, and if so how, such chemically distinct compounds interact with PfATP4, and how such interactions lead to parasite death, is not yet clear. The fact that multiple different chemical classes have converged upon PfATP4 highlights its significance as a potential target for new generation antimalarial agents. A spiroindolone (KAE609, now known as cipargamin) has progressed through Phase I and IIa clinical trials with favourable results. In this review we consider the physiological role of PfATP4, summarise the current repertoire of antimalarial compounds for which PfATP4 is implicated in their mechanism of action, and provide an outlook on translation from target identification in the laboratory to patient treatment in the field.
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Affiliation(s)
- Natalie Jane Spillman
- Research School of Biology, The Australian National University, Canberra, Australian Capital Territory 2601, Australia ; Department of Medicine (Infectious Diseases), Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Kiaran Kirk
- Research School of Biology, The Australian National University, Canberra, Australian Capital Territory 2601, Australia
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Piperazine scaffold: A remarkable tool in generation of diverse pharmacological agents. Eur J Med Chem 2015; 102:487-529. [PMID: 26310894 DOI: 10.1016/j.ejmech.2015.07.026] [Citation(s) in RCA: 136] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Revised: 07/13/2015] [Accepted: 07/15/2015] [Indexed: 12/21/2022]
Abstract
Piperazine is one of the most sought heterocyclics for the development of new drug candidates. This ring can be traced in a number of well established, commercially available drugs. Wide array of pharmacological activities exhibited by piperazine derivatives have made them indispensable anchors for the development of novel therapeutic agents. The review herein highlights the therapeutic significance of piperazine derivatives. Various therapeutically active piperazine derivatives developed by several chemists are reported here.
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29
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Role and Regulation of Glutathione Metabolism in Plasmodium falciparum. Molecules 2015; 20:10511-34. [PMID: 26060916 PMCID: PMC6272303 DOI: 10.3390/molecules200610511] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 05/11/2015] [Accepted: 06/01/2015] [Indexed: 11/30/2022] Open
Abstract
Malaria in humans is caused by one of five species of obligate intracellular protozoan parasites of the genus Plasmodium. P. falciparum causes the most severe disease and is responsible for 600,000 deaths annually, primarily in Sub-Saharan Africa. It has long been suggested that during their development, malaria parasites are exposed to environmental and metabolic stresses. One strategy to drug discovery was to increase these stresses by interfering with the parasites’ antioxidant and redox systems, which may be a valuable approach to disease intervention. Plasmodium possesses two redox systems—the thioredoxin and the glutathione system—with overlapping but also distinct functions. Glutathione is the most abundant low molecular weight redox active thiol in the parasites existing primarily in its reduced form representing an excellent thiol redox buffer. This allows for an efficient maintenance of the intracellular reducing environment of the parasite cytoplasm and its organelles. This review will highlight the mechanisms that are responsible for sustaining an adequate concentration of glutathione and maintaining its redox state in Plasmodium. It will provide a summary of the functions of the tripeptide and will discuss the potential of glutathione metabolism for drug discovery against human malaria parasites.
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Markus MB. Do hypnozoites cause relapse in malaria? Trends Parasitol 2015; 31:239-45. [DOI: 10.1016/j.pt.2015.02.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 02/01/2015] [Accepted: 02/20/2015] [Indexed: 12/25/2022]
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Morphological and Molecular Descriptors of the Developmental Cycle of Babesia divergens Parasites in Human Erythrocytes. PLoS Negl Trop Dis 2015; 9:e0003711. [PMID: 25955414 PMCID: PMC4425553 DOI: 10.1371/journal.pntd.0003711] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 03/19/2015] [Indexed: 11/19/2022] Open
Abstract
Human babesiosis, especially caused by the cattle derived Babesia divergens parasite, is on the increase, resulting in renewed attentiveness to this potentially life threatening emerging zoonotic disease. The molecular mechanisms underlying the pathophysiology and intra-erythrocytic development of these parasites are poorly understood. This impedes concerted efforts aimed at the discovery of novel anti-babesiacidal agents. By applying sensitive cell biological and molecular functional genomics tools, we describe the intra-erythrocytic development cycle of B. divergens parasites from immature, mono-nucleated ring forms to bi-nucleated paired piriforms and ultimately multi-nucleated tetrads that characterizes zoonotic Babesia spp. This is further correlated for the first time to nuclear content increases during intra-erythrocytic development progression, providing insight into the part of the life cycle that occurs during human infection. High-content temporal evaluation elucidated the contribution of the different stages to life cycle progression. Moreover, molecular descriptors indicate that B. divergens parasites employ physiological adaptation to in vitro cultivation. Additionally, differential expression is observed as the parasite equilibrates its developmental stages during its life cycle. Together, this information provides the first temporal evaluation of the functional transcriptome of B. divergens parasites, information that could be useful in identifying biological processes essential to parasite survival for future anti-babesiacidal discoveries.
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Campo B, Vandal O, Wesche DL, Burrows JN. Killing the hypnozoite--drug discovery approaches to prevent relapse in Plasmodium vivax. Pathog Glob Health 2015; 109:107-22. [PMID: 25891812 PMCID: PMC4455353 DOI: 10.1179/2047773215y.0000000013] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The eradication of malaria will only be possible if effective, well-tolerated medicines kill hypnozoites in vivax and ovale malaria, and thus prevent relapses in patients. Despite progress in the 8-aminoquinoline series, with tafenoquine in Phase III showing clear benefits over primaquine, the drug discovery challenge to identify hypnozoiticidal or hypnozoite-activating compounds has been hampered by the dearth of biological tools and assays, which in turn has been limited by the immense scientific and logistical challenges associated with accessing relevant human tissue and sporozoites. This review summarises the existing drug discovery series and approaches concerning the goal to block relapse.
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Affiliation(s)
- Brice Campo
- Medicines for Malaria Venture, Geneva, Switzerland
| | - Omar Vandal
- The Bill and Melinda Gates Foundation, Seattle, WA, USA
| | - David L. Wesche
- The Bill and Melinda Gates Foundation, Seattle, WA, USA
- Great Lakes Drug Development/Certara, Princeton, NJ, USA
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Interrogating alkyl and arylalkylpolyamino (bis)urea and (bis)thiourea isosteres as potent antimalarial chemotypes against multiple lifecycle forms of Plasmodium falciparum parasites. Bioorg Med Chem 2015; 23:5131-43. [PMID: 25684422 DOI: 10.1016/j.bmc.2015.01.036] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 01/20/2015] [Accepted: 01/21/2015] [Indexed: 01/28/2023]
Abstract
A new series of potent potent aryl/alkylated (bis)urea- and (bis)thiourea polyamine analogues were synthesized and evaluated in vitro for their antiplasmodial activity. Altering the carbon backbone and terminal substituents increased the potency of analogues in the compound library 3-fold, with the most active compounds, 15 and 16, showing half-maximal inhibitory concentrations (IC50 values) of 28 and 30 nM, respectively, against various Plasmodium falciparum parasite strains without any cross-resistance. In vitro evaluation of the cytotoxicity of these analogues revealed marked selectivity towards targeting malaria parasites compared to mammalian HepG2 cells (>5000-fold lower IC50 against the parasite). Preliminary biological evaluation of the polyamine analogue antiplasmodial phenotype revealed that (bis)urea compounds target parasite asexual proliferation, whereas (bis)thiourea compounds of the same series have the unique ability to block transmissible gametocyte forms of the parasite, indicating pluripharmacology against proliferative and non-proliferative forms of the parasite. In this manuscript, we describe these results and postulate a refined structure-activity relationship (SAR) model for antiplasmodial polyamine analogues. The terminally aryl/alkylated (bis)urea- and (bis)thiourea-polyamine analogues featuring a 3-5-3 or 3-6-3 carbon backbone represent a structurally novel and distinct class of potential antiplasmodials with activities in the low nanomolar range, and high selectivity against various lifecycle forms of P. falciparum parasites.
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Small-molecule xenomycins inhibit all stages of the Plasmodium life cycle. Antimicrob Agents Chemother 2014; 59:1427-34. [PMID: 25512429 DOI: 10.1128/aac.04704-14] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Widespread resistance to most antimalaria drugs in use has prompted the search for novel candidate compounds with activity against Plasmodium asexual blood stages to be developed for treatment. In addition, the current malaria eradication programs require the development of drugs that are effective against all stages of the parasite life cycle. We have analyzed the antimalarial properties of xenomycins, a novel subclass of small molecule compounds initially isolated for anticancer activity and similarity to quinacrine in biological effects on mammalian cells. In vitro studies show potent activity of Xenomycins against Plasmodium falciparum. Oral administration of xenomycins in mouse models result in effective clearance of liver and blood asexual and sexual stages, as well as effective inhibition of transmission to mosquitoes. These characteristics position xenomycins as antimalarial candidates with potential activity in prevention, treatment and elimination of this disease.
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Identification and deconvolution of cross-resistance signals from antimalarial compounds using multidrug-resistant Plasmodium falciparum strains. Antimicrob Agents Chemother 2014; 59:1110-8. [PMID: 25487796 DOI: 10.1128/aac.03265-14] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Plasmodium falciparum, the most deadly agent of malaria, displays a wide variety of resistance mechanisms in the field. The ability of antimalarial compounds in development to overcome these must therefore be carefully evaluated to ensure uncompromised activity against real-life parasites. We report here on the selection and phenotypic as well as genotypic characterization of a panel of sensitive and multidrug-resistant P. falciparum strains that can be used to optimally identify and deconvolute the cross-resistance signals from an extended panel of investigational antimalarials. As a case study, the effectiveness of the selected panel of strains was demonstrated using the 1,2,4-oxadiazole series, a newly identified antimalarial series of compounds with in vitro activity against P. falciparum at nanomolar concentrations. This series of compounds was to be found inactive against several multidrug-resistant strains, and the deconvolution of this signal implicated pfcrt, the genetic determinant of chloroquine resistance. Targeted mode-of-action studies further suggested that this new chemical series might act as falcipain 2 inhibitors, substantiating the suggestion that these compounds have a site of action similar to that of chloroquine but a distinct mode of action. New antimalarials must overcome existing resistance and, ideally, prevent its de novo appearance. The panel of strains reported here, which includes recently collected as well as standard laboratory-adapted field isolates, is able to efficiently detect and precisely characterize cross-resistance and, as such, can contribute to the faster development of new, effective antimalarial drugs.
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Affiliation(s)
- David S Barnett
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital , Memphis, Tennessee 38105, United States
| | - R Kiplin Guy
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital , Memphis, Tennessee 38105, United States
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