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Tran L, Tu VL, Dadam MN, Aziz JMA, Duy TLD, Ahmed HHH, Kwaah PA, Quoc HN, Van Dat T, Mizuta S, Hirayama K, Huy NT. Antimalarial activities of benzothiazole analogs: A systematic review. Fundam Clin Pharmacol 2024; 38:410-464. [PMID: 38146774 DOI: 10.1111/fcp.12974] [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: 05/06/2023] [Revised: 09/25/2023] [Accepted: 11/10/2023] [Indexed: 12/27/2023]
Abstract
BACKGROUND Benzothiazole derivatives have been reported to possess a wide range of biological activities, including antimalarial activity. This systematic review aims to summarize and evaluate the antimalarial activities of benzothiazole analogs. METHODS We conducted an electronic search using nine databases in October 2017 and subsequently updated in September 2022. We included all original in vitro and in vivo studies that documented the antimalarial activities of compounds containing benzothiazole analogs with no restriction. The risk of bias of each included study was assessed by ToxRTool. RESULTS Twenty-eight articles were included in our study, which are in vitro, in vivo, or both. Of these, 232 substances were identified to have potent antiplasmodial activity against various strains of the malaria parasite. Benzothiazole analogs show different antimalarial mechanisms, including inhibition of Plasmodium falciparum enzymes in in vitro studies and inhibition of blood parasites in in vivo studies. CONCLUSIONS Benzothiazole derivatives are promising substances for treating malaria. The structure-activity relationship studies suggest that the substitution pattern of the benzothiazole scaffold plays a crucial role in determining the antimalarial activity of the analog.
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Affiliation(s)
- Linh Tran
- Institute of Fundamental and Applied Sciences, Duy Tan University, Ho Chi Minh City, Vietnam
- Faculty of Natural Sciences, Duy Tan University, Da Nang, Vietnam
| | - Vo Linh Tu
- Online Research Club (https://www.onlineresearchclub.org/), Nagasaki, Japan
- Faculty of Traditional Medicine, University of Medicine and Pharmacy at Ho Chi Minh City, Ho Chi Minh City, Vietnam
| | - Mohammad Najm Dadam
- Online Research Club (https://www.onlineresearchclub.org/), Nagasaki, Japan
- Department of Geriatrics, Helios Klinikum Schwelm, Schwelm, Germany
| | - Jeza Muhamad Abdul Aziz
- Biomedical Science Department, Komar University of Science and Technology, Sulaimaniyah, Kurdistan Region, Iraq
- Baxshin Research Center, Baxshin Hospital, Sulaimaniyah, Kurdistan Region, Iraq
| | - Tran Le Dinh Duy
- Online Research Club (https://www.onlineresearchclub.org/), Nagasaki, Japan
- College of Health Sciences, VinUniversity, Hanoi, Vietnam
| | - Hajer Hatim Hassan Ahmed
- Online Research Club (https://www.onlineresearchclub.org/), Nagasaki, Japan
- Faculty of Medicine, Alzaiem Alazhari University, Khartoum, Sudan
| | - Patrick Amanning Kwaah
- Online Research Club (https://www.onlineresearchclub.org/), Nagasaki, Japan
- Department of Internal Medicine, Yale School of Medicine, Yale-Waterbury Internal Medicine Program, Waterbury, Connecticut, USA
| | - Hoang Nghia Quoc
- Online Research Club (https://www.onlineresearchclub.org/), Nagasaki, Japan
- Vietnam Military Medical University, Hanoi, Vietnam
| | - Truong Van Dat
- Ministry of Health Cabinet, Ministry of Health, Ha Noi, Vietnam
| | - Satoshi Mizuta
- Center for Bioinformatics and Molecular Medicine, Nagasaki University, Nagasaki, Japan
| | - Kenji Hirayama
- School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan
| | - Nguyen Tien Huy
- Institute of Fundamental and Applied Sciences, Duy Tan University, Ho Chi Minh City, Vietnam
- Faculty of Natural Sciences, Duy Tan University, Da Nang, Vietnam
- Online Research Club (https://www.onlineresearchclub.org/), Nagasaki, Japan
- School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan
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Escala N, Pineda LM, Ng MG, Coronado LM, Spadafora C, del Olmo E. Antiplasmodial activity, structure-activity relationship and studies on the action of novel benzimidazole derivatives. Sci Rep 2023; 13:285. [PMID: 36609676 PMCID: PMC9822940 DOI: 10.1038/s41598-022-27351-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 12/30/2022] [Indexed: 01/08/2023] Open
Abstract
Malaria cases and deaths keep being excessively high every year. Some inroads gained in the last two decades have been eroded especially due to the surge of resistance to most antimalarials. The search for new molecules that can replace the ones currently in use cannot stop. In this report, the synthesis of benzimidazole derivatives guided by structure-activity parameters is presented. Thirty-six molecules obtained are analyzed according to their activity against P. falciparum HB3 strain based on the type of substituent on rings A and B, their electron donor/withdrawing, as well as their dimension/spatial properties. There is a preference for electron donating groups on ring A, such as Me in position 5, or better, 5, 6-diMe. Ring B must be of the pyridine type such as picolinamide, other modifications are generally not favorable. Two molecules, 1 and 33 displayed antiplasmodial activity in the high nanomolar range against the chloroquine sensitive strain, with selectivity indexes above 10. Activity results of 1, 12 and 16 on a chloroquine resistance strain indicated an activity close to chloroquine for compound 1. Analysis of some of their effect on the parasites seem to suggest that 1 and 33 affect only the parasite and use a route other than interference with hemozoin biocrystallization, the route used by chloroquine and most antimalarials.
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Affiliation(s)
- Nerea Escala
- grid.452531.4Departamento de Ciencias Farmacéuticas: Química Farmacéutica, Facultad de Farmacia, Universidad de Salamanca, CIETUS, IBSAL, 37007 Salamanca, Spain
| | - Laura M. Pineda
- Center of Cellular and Molecular Biology of Diseases, Instituto de Investigaciones Científicas y Servicios de Alta Tecnología, City of Knowledge, Clayton, Apartado 0816-02852, Panama City, Panama
| | - Michelle G. Ng
- Center of Cellular and Molecular Biology of Diseases, Instituto de Investigaciones Científicas y Servicios de Alta Tecnología, City of Knowledge, Clayton, Apartado 0816-02852, Panama City, Panama
| | - Lorena M. Coronado
- Center of Cellular and Molecular Biology of Diseases, Instituto de Investigaciones Científicas y Servicios de Alta Tecnología, City of Knowledge, Clayton, Apartado 0816-02852, Panama City, Panama
| | - Carmenza Spadafora
- Center of Cellular and Molecular Biology of Diseases, Instituto de Investigaciones Científicas y Servicios de Alta Tecnología, City of Knowledge, Clayton, Apartado 0816-02852, Panama City, Panama.
| | - Esther del Olmo
- grid.452531.4Departamento de Ciencias Farmacéuticas: Química Farmacéutica, Facultad de Farmacia, Universidad de Salamanca, CIETUS, IBSAL, 37007 Salamanca, Spain
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Sousa CC, Dziwornu GA, Quadros HC, Araujo-Neto JH, Chibale K, Moreira DRM. Antimalarial Pyrido[1,2- a]benzimidazoles Exert Strong Parasiticidal Effects by Achieving High Cellular Uptake and Suppressing Heme Detoxification. ACS Infect Dis 2022; 8:1700-1710. [PMID: 35848708 DOI: 10.1021/acsinfecdis.2c00326] [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: 11/29/2022]
Abstract
Pyrido[1,2-a]benzimidazoles (PBIs) are synthetic antiplasmodium agents with potent activity and are structurally differentiated from benchmark antimalarials. To study the cellular uptake of PBIs and understand the underlying phenotype of their antiplasmodium activity, their antiparasitic activities were examined in chloroquine (CQ)-susceptible and CQ-resistant Plasmodium falciparum in vitro. Moreover, drug uptake and heme detoxification suppression were examined in Plasmodium berghei-infected mice. The in vitro potency of PBIs is comparable to most 4-aminoquinolines. They have a speed of action in vitro that is superior to that of atovaquone and an ability to kill rings and trophozoites. The antiparasitic effects observed for the PBIs in cell culture and in infected mice are similar in terms of potency and efficacy and are comparable to CQ but with the added advantage of demonstrating equipotency against both CQ susceptible and resistant parasite strains. PBIs have a high rate of uptake by parasite cells and, conversely, a limited rate of uptake by host cells. The mechanism of cellular uptake of the PBIs differs from the ion-trap mechanism typically observed for 4-aminoquinolines, although they share key structural features. The high cellular uptake, attractive parasiticidal profile, and susceptibility of resistant strains to PBIs are desirable characteristics for new antimalarial agents.
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Affiliation(s)
- Caroline C Sousa
- Fundação Oswaldo Cruz (Fiocruz), Instituto Gonçalo Moniz, Salvador, 40296-710 Bahia, Brazil
| | - Godwin Akpeko Dziwornu
- South African Medical Research Council Drug Discovery and Development Research Unit, Department of Chemistry and Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Rondebosch 7701, South Africa
| | - Helenita C Quadros
- Fundação Oswaldo Cruz (Fiocruz), Instituto Gonçalo Moniz, Salvador, 40296-710 Bahia, Brazil
| | | | - Kelly Chibale
- South African Medical Research Council Drug Discovery and Development Research Unit, Department of Chemistry and Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Rondebosch 7701, South Africa
| | - Diogo R M Moreira
- Fundação Oswaldo Cruz (Fiocruz), Instituto Gonçalo Moniz, Salvador, 40296-710 Bahia, Brazil
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Murithi JM, Deni I, Pasaje CFA, Okombo J, Bridgford JL, Gnädig NF, Edwards RL, Yeo T, Mok S, Burkhard AY, Coburn-Flynn O, Istvan ES, Sakata-Kato T, Gomez-Lorenzo MG, Cowell AN, Wicht KJ, Le Manach C, Kalantarov GF, Dey S, Duffey M, Laleu B, Lukens AK, Ottilie S, Vanaerschot M, Trakht IN, Gamo FJ, Wirth DF, Goldberg DE, Odom John AR, Chibale K, Winzeler EA, Niles JC, Fidock DA. The Plasmodium falciparum ABC transporter ABCI3 confers parasite strain-dependent pleiotropic antimalarial drug resistance. Cell Chem Biol 2022; 29:824-839.e6. [PMID: 34233174 PMCID: PMC8727639 DOI: 10.1016/j.chembiol.2021.06.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 05/24/2021] [Accepted: 06/14/2021] [Indexed: 01/21/2023]
Abstract
Widespread Plasmodium falciparum resistance to first-line antimalarials underscores the vital need to develop compounds with novel modes of action and identify new druggable targets. Here, we profile five compounds that potently inhibit P. falciparum asexual blood stages. Resistance selection studies with three carboxamide-containing compounds, confirmed by gene editing and conditional knockdowns, identify point mutations in the parasite transporter ABCI3 as the primary mediator of resistance. Selection studies with imidazopyridine or quinoline-carboxamide compounds also yield changes in ABCI3, this time through gene amplification. Imidazopyridine mode of action is attributed to inhibition of heme detoxification, as evidenced by cellular accumulation and heme fractionation assays. For the copy-number variation-selecting imidazopyridine and quinoline-carboxamide compounds, we find that resistance, manifesting as a biphasic concentration-response curve, can independently be mediated by mutations in the chloroquine resistance transporter PfCRT. These studies reveal the interconnectedness of P. falciparum transporters in overcoming drug pressure in different parasite strains.
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Affiliation(s)
- James M. Murithi
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Ioanna Deni
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | | | - John Okombo
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Jessica L. Bridgford
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Nina F. Gnädig
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Rachel L. Edwards
- Division of Infectious Diseases, Allergy and Immunology, Center for Vaccine Development, St. Louis University, St. Louis, MO 63104, USA
| | - Tomas Yeo
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Sachel Mok
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Anna Y. Burkhard
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Olivia Coburn-Flynn
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Eva S. Istvan
- Department of Medicine, Division of Infectious Diseases, and Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Tomoyo Sakata-Kato
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA,Infectious Disease and Microbiome Program, Broad Institute, Cambridge, MA 02142, USA
| | | | - Annie N. Cowell
- School of Medicine, University of California San Diego (UCSD), La Jolla, CA 92093, USA
| | - Kathryn J. Wicht
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA,Drug Discovery and Development Center (H3D) and South African Medical Research Council Drug Discovery and Development Research Unit, Department of Chemistry and Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Rondebosch 7701, South Africa
| | - Claire Le Manach
- Drug Discovery and Development Center (H3D) and South African Medical Research Council Drug Discovery and Development Research Unit, Department of Chemistry and Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Rondebosch 7701, South Africa
| | - Gavreel F. Kalantarov
- Division of Experimental Therapeutics, Department of Medicine, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Sumanta Dey
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Maëlle Duffey
- Medicines for Malaria Venture, 1215 Geneva, Switzerland
| | - Benoît Laleu
- Medicines for Malaria Venture, 1215 Geneva, Switzerland
| | - Amanda K. Lukens
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA,Infectious Disease and Microbiome Program, Broad Institute, Cambridge, MA 02142, USA
| | - Sabine Ottilie
- School of Medicine, University of California San Diego (UCSD), La Jolla, CA 92093, USA
| | - Manu Vanaerschot
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Ilya N. Trakht
- Division of Experimental Therapeutics, Department of Medicine, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Francisco-Javier Gamo
- Global Health Pharma Research Unit, GlaxoSmithKline, 28760 Tres Cantos, Madrid, Spain
| | - Dyann F. Wirth
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA,Infectious Disease and Microbiome Program, Broad Institute, Cambridge, MA 02142, USA
| | - Daniel E. Goldberg
- Department of Medicine, Division of Infectious Diseases, and Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | | | - Kelly Chibale
- Drug Discovery and Development Center (H3D) and South African Medical Research Council Drug Discovery and Development Research Unit, Department of Chemistry and Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Rondebosch 7701, South Africa
| | - Elizabeth A. Winzeler
- School of Medicine, University of California San Diego (UCSD), La Jolla, CA 92093, USA
| | - Jacquin C. Niles
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - David A. Fidock
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA,Division of Infectious Diseases, Department of Medicine, Columbia University Irving Medical Center, New York, NY 10032, USA,Corresponding author
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5
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Olivier T, Loots L, Kok M, de Villiers M, Reader J, Birkholtz LM, Arnott GE, de Villiers KA. Adsorption to the Surface of Hemozoin Crystals: Structure-Based Design and Synthesis of Amino-Phenoxazine β-Hematin Inhibitors. ChemMedChem 2022; 17:e202200139. [PMID: 35385211 PMCID: PMC9119941 DOI: 10.1002/cmdc.202200139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 04/05/2022] [Indexed: 11/07/2022]
Abstract
In silico adsorption of eight antimalarials that inhibit β-hematin (synthetic hemozoin) formation identified a primary binding site on the (001) face, which accommodates inhibitors via formation of predominantly π-π interactions. A good correlation (r2 =0.64, P=0.017) between adsorption energies and the logarithm of β-hematin inhibitory activity was found for this face. Of 53 monocyclic, bicyclic and tricyclic scaffolds, the latter yielded the most favorable adsorption energies. Five new amino-phenoxazine compounds were pursued as β-hematin inhibitors based on adsorption behaviour. The 2-substituted phenoxazines show good to moderate β-hematin inhibitory activity (<100 μM) and Plasmodium falciparum blood stage activity against the 3D7 strain. N1 ,N1 -diethyl-N4 -(10H-phenoxazin-2-yl)pentane-1,4-diamine (P2a) is the most promising hit with IC50 values of 4.7±0.6 and 0.64±0.05 μM, respectively. Adsorption energies are predictive of β-hematin inhibitory activity, and thus the in silico approach is a beneficial tool for structure-based development of new non-quinoline inhibitors.
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Affiliation(s)
- Tania Olivier
- Department of Chemistry and Polymer Science, Stellenbosch University, Private BagX1, Matieland, 7602, South Africa
| | - Leigh Loots
- Department of Chemistry and Polymer Science, Stellenbosch University, Private BagX1, Matieland, 7602, South Africa
| | - Michélle Kok
- Department of Biochemistry, Stellenbosch University, Private BagX1, Matieland, 7602, South Africa
| | - Marianne de Villiers
- Department of Biochemistry, Stellenbosch University, Private BagX1, Matieland, 7602, South Africa
| | - Janette Reader
- Department of Biochemistry, Genetics and Microbiology, Institute for Sustainable Malaria Control, University of Pretoria, Pretoria, 0028, South Africa
| | - Lyn-Marié Birkholtz
- Department of Biochemistry, Genetics and Microbiology, Institute for Sustainable Malaria Control, University of Pretoria, Pretoria, 0028, South Africa
| | - Gareth E Arnott
- Department of Chemistry and Polymer Science, Stellenbosch University, Private BagX1, Matieland, 7602, South Africa
| | - Katherine A de Villiers
- Department of Chemistry and Polymer Science, Stellenbosch University, Private BagX1, Matieland, 7602, South Africa
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The Role of the Iron Protoporphyrins Heme and Hematin in the Antimalarial Activity of Endoperoxide Drugs. Pharmaceuticals (Basel) 2022; 15:ph15010060. [PMID: 35056117 PMCID: PMC8779033 DOI: 10.3390/ph15010060] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 12/01/2021] [Accepted: 12/08/2021] [Indexed: 02/05/2023] Open
Abstract
Plasmodium has evolved to regulate the levels and oxidative states of iron protoporphyrin IX (Fe-PPIX). Antimalarial endoperoxides such as 1,2,4-trioxane artemisinin and 1,2,4-trioxolane arterolane undergo a bioreductive activation step mediated by heme (FeII-PPIX) but not by hematin (FeIII-PPIX), leading to the generation of a radical species. This can alkylate proteins vital for parasite survival and alkylate heme into hematin–drug adducts. Heme alkylation is abundant and accompanied by interconversion from the ferrous to the ferric state, which may induce an imbalance in the iron redox homeostasis. In addition to this, hematin–artemisinin adducts antagonize the spontaneous biomineralization of hematin into hemozoin crystals, differing strikingly from artemisinins, which do not directly suppress hematin biomineralization. These hematin–drug adducts, despite being devoid of the peroxide bond required for radical-induced alkylation, are powerful antiplasmodial agents. This review addresses our current understanding of Fe-PPIX as a bioreductive activator and molecular target. A compelling pharmacological model is that by alkylating heme, endoperoxide drugs can cause an imbalance in the iron homeostasis and that the hematin–drug adducts formed have strong cytocidal effects by possibly reproducing some of the toxifying effects of free Fe-PPIX. The antiplasmodial phenotype and the mode of action of hematin–drug adducts open new possibilities for reconciliating the mechanism of endoperoxide drugs and for malaria intervention.
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Studies of Potency and Efficacy of an Optimized Artemisinin-Quinoline Hybrid against Multiple Stages of the Plasmodium Life Cycle. Pharmaceuticals (Basel) 2021; 14:ph14111129. [PMID: 34832911 PMCID: PMC8620906 DOI: 10.3390/ph14111129] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 11/02/2021] [Accepted: 11/03/2021] [Indexed: 11/23/2022] Open
Abstract
A recently developed artemisinin-quinoline hybrid, named 163A, has been shown to display potent activity against the asexual blood stage of Plasmodium, the malaria parasite. In this study, we determined its in vitro cytotoxicity to mammalian cells, its potency to suppress P. berghei hepatic infection and to decrease the viability of P. falciparum gametocytes, in addition to determining whether the drug exhibits efficacy of a P. berghei infection in mice. This hybrid compound has a low level of cytotoxicity to mammalian cells and, conversely, a high level of selectivity. It is potent in the prevention of hepatic stage development as well as in killing gametocytes, denoting a potential blockage of malaria transmission. The hybrid presents a potent inhibitory activity for beta-hematin crystal formation, in which subsequent assays revealed that its endoperoxide component undergoes bioactivation by reductive reaction with ferrous heme towards the formation of heme-drug adducts; in parallel, the 7-chloroquinoline component has binding affinity for ferric hemin. Both structural components of the hybrid co-operate to enhance the inhibition of beta-hematin, and this bitopic ligand property is essential for arresting the growth of asexual blood parasites. We demonstrated the in vivo efficacy of the hybrid as an erythrocytic schizonticide agent in comparison to a chloroquine/artemisinin combination therapy. Collectively, the findings suggest that the bitopic property of the hybrid is highly operative on heme detoxification suppression, and this provides compelling evidence for explaining the action of the hybrid on the asexual blood stage. For sporozoite and gametocyte stages, the hybrid conserves the potency typically observed for endoperoxide drugs, and this is possibly achieved due to the redox chemistry of endoperoxide components with ferrous heme.
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de Villiers KA, Egan TJ. Heme Detoxification in the Malaria Parasite: A Target for Antimalarial Drug Development. Acc Chem Res 2021; 54:2649-2659. [PMID: 33982570 DOI: 10.1021/acs.accounts.1c00154] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Over the last century, malaria deaths have decreased by more than 85%. Nonetheless, there were 405 000 deaths in 2018, mostly resulting from Plasmodium falciparum infection. In the 21st century, much of the advance has arisen from the deployment of insecticide-treated bed nets and artemisinin combination therapy. However, over the past few decades parasites with a delayed artemisinin clearance phenotype have appeared in Southeast Asia, threatening further gains. The effort to find new drugs is thus urgent. A prominent process in blood stage malaria parasites, which we contend remains a viable drug target, is hemozoin formation. This crystalline material consisting of heme can be readily seen when parasites are viewed microscopically. The process of its formation in the parasite, however, is still not fully understood.In early work, we recognized hemozoin formation as a biomineralization process. We have subsequently investigated the kinetics of synthetic hemozoin (β-hematin) crystallization catalyzed at lipid-aqueous interfaces under biomimetic conditions. This led us to the use of neutral detergent-based high-throughput screening (HTS) for inhibitors of β-hematin formation. A good hit rate against malaria parasites was obtained. Simultaneously, we developed a pyridine-based assay which proved successful in measuring the concentrations of hematin not converted to β-hematin.The pyridine assay was adapted to determine the effects of chloroquine and other clinical antimalarials on hemozoin formation in the cell. This permitted the determination of the dose-dependent amounts of exchangeable heme and hemozoin in P. falciparum for the first time. These studies have shown that hemozoin inhibitors cause a dose-dependent increase in exchangeable heme, correlated with decreased parasite survival. Electron spectroscopic imaging (ESI) showed a relocation of heme iron into the parasite cytoplasm, while electron microscopy provided evidence of the disruption of hemozoin crystals. This cellular assay was subsequently extended to top-ranked hits from a wide range of scaffolds found by HTS. Intriguingly, the amounts of exchangeable heme at the parasite growth IC50 values of these scaffolds showed substantial variation. The amount of exchangeable heme was found to be correlated with the amount of inhibitor accumulated in the parasitized red blood cell. This suggests that heme-inhibitor complexes, rather than free heme, lead to parasite death. This was supported by ESI using a Br-containing compound which showed the colocalization of Fe and Br as well as by confocal Raman microscopy which confirmed the presence of a complex in the parasite. Current evidence indicates that inhibitors block hemozoin formation by surface adsorption. Indeed, we have successfully introduced molecular docking with hemozoin to find new inhibitors. It follows that the resulting increase in free heme leads to the formation of the parasiticidal heme-inhibitor complex. We have reported crystal structures of heme-drug complexes for several aryl methanol antimalarials in nonaqueous media. These form coordination complexes but most other inhibitors interact noncovalently, and the determination of their structures remains a major challenge.It is our view that key future developments will include improved assays to measure cellular heme levels, better in silico approaches for predicting β-hematin inhibition, and a concerted effort to determine the structure and properties of heme-inhibitor complexes.
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Affiliation(s)
- Katherine A. de Villiers
- Department of Chemistry and Polymer Science, Stellenbosch University, Private Bag, Matieland 7600, South Africa
| | - Timothy J. Egan
- Department of Chemistry, University of Cape Town, Private Bag, Rondebosch 7701, South Africa
- Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Observatory, Cape Town 7945, South Africa
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