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Sustainable Radical Cure of the Latent Malarias. Infect Dis (Lond) 2023. [DOI: 10.1007/978-1-0716-2463-0_896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
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Akide Ndunge OB, Kilian N, Salman MM. Cerebral Malaria and Neuronal Implications of Plasmodium Falciparum Infection: From Mechanisms to Advanced Models. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2202944. [PMID: 36300890 PMCID: PMC9798991 DOI: 10.1002/advs.202202944] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 09/22/2022] [Indexed: 06/01/2023]
Abstract
Reorganization of host red blood cells by the malaria parasite Plasmodium falciparum enables their sequestration via attachment to the microvasculature. This artificially increases the dwelling time of the infected red blood cells within inner organs such as the brain, which can lead to cerebral malaria. Cerebral malaria is the deadliest complication patients infected with P. falciparum can experience and still remains a major public health concern despite effective antimalarial therapies. Here, the current understanding of the effect of P. falciparum cytoadherence and their secreted proteins on structural features of the human blood-brain barrier and their involvement in the pathogenesis of cerebral malaria are highlighted. Advanced 2D and 3D in vitro models are further assessed to study this devastating interaction between parasite and host. A better understanding of the molecular mechanisms leading to neuronal and cognitive deficits in cerebral malaria will be pivotal in devising new strategies to treat and prevent blood-brain barrier dysfunction and subsequent neurological damage in patients with cerebral malaria.
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Affiliation(s)
- Oscar Bate Akide Ndunge
- Department of Internal MedicineSection of Infectious DiseasesYale University School of Medicine300 Cedar StreetNew HavenCT06510USA
| | - Nicole Kilian
- Centre for Infectious Diseases, ParasitologyHeidelberg University HospitalIm Neuenheimer Feld 32469120HeidelbergGermany
| | - Mootaz M. Salman
- Department of PhysiologyAnatomy and GeneticsUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for NanoScience DiscoveryUniversity of OxfordOxfordUK
- Oxford Parkinson's Disease CentreUniversity of OxfordOxfordUK
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Combination Therapy Strategies for the Treatment of Malaria. Molecules 2019; 24:molecules24193601. [PMID: 31591293 PMCID: PMC6804225 DOI: 10.3390/molecules24193601] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2019] [Revised: 08/15/2019] [Accepted: 08/21/2019] [Indexed: 11/16/2022] Open
Abstract
Malaria is a vector- and blood-borne infection that is responsible for a large number of deaths around the world. Most of the currently used antimalarial therapeutics suffer from drug resistance. The other limitations associated with the currently used antimalarial drugs are poor drug bioavailability, drug toxicity, and poor water solubility. Combination therapy is one of the best approaches that is currently used to treat malaria, whereby two or more therapeutic agents are combined. Different combination therapy strategies are used to overcome the aforementioned limitations. This review article reports two strategies of combination therapy; the incorporation of two or more antimalarials into polymer-based carriers and hybrid compounds designed by hybridization of two antimalarial pharmacophores.
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Abstract
The technical genesis and practice of 8-aminoquinoline therapy of latent malaria offer singular scientific, clinical, and public health insights. The 8-aminoquinolines brought revolutionary scientific discoveries, dogmatic practices, benign neglect, and, finally, enduring promise against endemic malaria. The clinical use of plasmochin-the first rationally synthesized blood schizontocide and the first gametocytocide, tissue schizontocide, and hypnozoitocide of any kind-commenced in 1926. Plasmochin became known to sometimes provoke fatal hemolytic crises. World War II delivered a newer 8-aminoquinoline, primaquine, and the discovery of glucose-6-phosphate dehydrogenase (G6PD) deficiency as the basis of its hemolytic toxicity came in 1956. Primaquine nonetheless became the sole therapeutic option against latent malaria. After 40 years of fitful development, in 2018 the U.S. Food and Drug Administration registered the 8-aminoquinoline called tafenoquine for the prevention of all malarias and the treatment of those that relapse. Tafenoquine also cannot be used in G6PD-unknown or -deficient patients. The hemolytic toxicity of the 8-aminoquinolines impedes their great potential, but this problem has not been a research priority. This review explores the complex technical dimensions of the history of 8-aminoquinolines. The therapeutic principles thus examined may be leveraged in improved practice and in understanding the bright prospect of discovery of newer drugs that cannot harm G6PD-deficient patients.
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Olanlokun JO, Balogun FA, Olorunsogo OO. Chemotherapeutic and prophylactic antimalarial drugs induce cell death through mitochondrial-mediated apoptosis in murine models. Drug Chem Toxicol 2018; 44:47-57. [PMID: 30486696 DOI: 10.1080/01480545.2018.1536139] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Malaria is a parasitic disease that has defied many treatment plans. This study was carried out to investigate the host mitochondrial response to malarial infection and selected antimalarial chemotherapy using murine models. The effects of artesunate (ART) and proguanil (PRG) on mitochondrial Permeability Transition (mPT), mitochondrial ATPase (mATPase), level of malondialdehyde (MDA) and activities of antioxidant enzymes; catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), Xanthine oxidase (XO), glutathione S-transferase (GST) and reduced glutathione (GSH) were estimated in Plasmodium berghei-infected mice treated with ART and PRG. Besides, apoptotic markers, such as caspases 3, 9 and DNA fragmentation were estimated. Unparasitised (NORMAL) and parasitized but untreated (PU) animals were used as controls. The mPT pore opening fold of 9 (ART), 3 (PRG), and 4 (PU) were observed relative to calcium (23) for in vivo study. In vitro, graded concentrations (20, 40, 80 and 160 μg/mL) of ART gave mPT induction folds of 1, 21, 23 and 25, respectively, relative to calcium (9) while PRG did not have effect in the absence of calcium. In vivo, ART significantly (p < 0.001) enhanced mATPase activity than PRG. The PRG and ART increased the MDA levels in vivo. Oral administration of ART and PRG altered antioxidant enzymes status, Caspases 3 and 9 were significantly activated in PRG-treated groups; there was significant increase in DNA fragmentation in PU and PRG groups compared with the normal control. The results obtained showed that malaria parasite and antimalarial drugs cause mitochondrial-mediated apoptosis.
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Affiliation(s)
- John Oludele Olanlokun
- Laboratories for Biomembrane Research and Biotechnology, Department of Biochemistry, Faculty of Basic Medical Sciences, College of Medicine, University of Ibadan, Ibadan, Nigeria
| | - Folashade Abimbola Balogun
- Laboratories for Biomembrane Research and Biotechnology, Department of Biochemistry, Faculty of Basic Medical Sciences, College of Medicine, University of Ibadan, Ibadan, Nigeria
| | - Olufunso Olabode Olorunsogo
- Laboratories for Biomembrane Research and Biotechnology, Department of Biochemistry, Faculty of Basic Medical Sciences, College of Medicine, University of Ibadan, Ibadan, Nigeria
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Spring MD, Pichyangkul S, Lon C, Gosi P, Yongvanichit K, Srichairatanakul U, Limsalakpeth A, Chaisatit C, Chann S, Sriwichai S, Auayapon M, Chaorattanakawee S, Dutta S, Prom S, Meng Chour C, Walsh DS, Angov E, Saunders DL. Antibody profiles to plasmodium merozoite surface protein-1 in Cambodian adults during an active surveillance cohort with nested treatment study. Malar J 2016; 15:17. [PMID: 26747132 PMCID: PMC4706704 DOI: 10.1186/s12936-015-1058-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2015] [Accepted: 12/17/2015] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND In addition to evidence for a protective role of antibodies to the malaria blood stage antigen merozoite surface protein 1 (MSP1), MSP1 antibodies are also considered as a marker of past malaria exposure in sero-epidemiological studies. METHODS In order to better assess the potential use of MSP1 serology in malaria chemoprophylaxis trials in endemic areas, an analysis for the prevalence of antibodies to both Plasmodium falciparum and Plasmodium vivax MSP142 in healthy Cambodian adults was conducted at two sites as part of an active, observational cohort evaluating the efficacy of dihydroartemisinin-piperaquine (DP) for uncomplicated malaria (ClinicalTrials.gov identifier NCT01280162). RESULTS Rates of baseline sero-positivity were high (59 and 73% for PfMSP142 and PvMSP142, respectively), and titers higher in those who lived in a higher transmission area, although there was little correlation in titers between the two species. Those volunteers who subsequently went on to develop malaria had higher baseline MSP142 titers than those who did not for both species. Titers to both antigens remained largely stable over the course of the 4-6 month study, except in those infected with P. falciparum who had multiple recurrences. CONCLUSION These findings illuminate the difficulties in using MSP142 serology as either a screening criterion and/or biomarker of exposure in chemoprophylaxis studies. Further work remains to identify useful markers of malarial infection and/or immunity.
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Affiliation(s)
- Michele D Spring
- Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand.
| | - Sathit Pichyangkul
- Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand.
| | - Chanthap Lon
- Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand.
| | - Panita Gosi
- Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand.
| | - Kosol Yongvanichit
- Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand.
| | | | - Amporn Limsalakpeth
- Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand.
| | - Chaiyaporn Chaisatit
- Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand.
| | - Soklyda Chann
- Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand.
| | - Sabaithip Sriwichai
- Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand.
| | - Montida Auayapon
- Center of Excellence for Biomedical and Public Health Informatics (BIOPHICS), Bangkok, Thailand.
| | | | - Sheetij Dutta
- Walter Reed Army Institute of Research, Silver Spring, MD, USA.
| | | | - Char Meng Chour
- National Center for Parasitology, Entomology and Malaria Control (CNM), Phnom Penh, Cambodia.
| | | | - Evelina Angov
- Walter Reed Army Institute of Research, Silver Spring, MD, USA.
| | - David L Saunders
- Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand.
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Summary of anti-malarial prophylactic efficacy of tafenoquine from three placebo-controlled studies of residents of malaria-endemic countries. Malar J 2015; 14:473. [PMID: 26610844 PMCID: PMC4661991 DOI: 10.1186/s12936-015-0991-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 11/05/2015] [Indexed: 11/16/2022] Open
Abstract
Background Tafenoquine is a long half-life primaquine analog being developed for malaria prophylaxis. The US Army recently performed a unified analysis of efficacy in preparation for a regulatory submission, utilizing legacy data from three placebo-controlled studies conducted in the late 1990s and early 2000s. The subjects were residents of Africa who were naturally exposed to Plasmodium falciparum for 12–26 weeks. Methods The prophylactic efficacy of tafenoquine and mefloquine (included in some studies as a comparator) was calculated using incidence density among subjects who had completed the three-day loading doses of study drug, had at least one maintenance dose and had at least one blood smear assessed during the prophylactic period. The three placebo-controlled studies were analysed separately and then in two pooled analyses: one for tafenoquine versus placebo (three studies) and one for tafenoquine and mefloquine versus placebo (two studies). Results The pooled protective efficacy (PE) of a tafenoquine regimen with three daily loading doses plus weekly maintenance at 200-mg for 10 weeks or longer (referred to as 200-mg weekly hereafter) relative to placebo in three placebo-controlled studies was 93.1 % [95 % confidence interval (CI) 89.1–95.6 %; total N = 492]. The pooled PEs of regimens of tafenoquine 200-mg weekly and mefloquine 250-mg weekly relative to placebo in two placebo-controlled studies (total N = 519) were 93.5 % (95 % CI 88.6–96.2 %) and 94.5 % (95 % CI 88.7–97.3 %), respectively. Three daily loading plus weekly maintenance doses of 50- and 100-mg, but not 25-mg, exhibited similar PEs. The PEs of tafenoquine regimens of a three-day loading dose at 400-mg with and without follow-up weekly maintenance doses at 400-mg were 93.7 % (95 % CI 85.4–97.3 %) and 81.0 % (95 % CI 66.8–89.1 %), respectively. Conclusions Tafenoquine provided the same level of prophylactic efficacy as mefloquine in residents of Africa. These data support the prophylactic efficacy of tafenoquine and mefloquine that has already been demonstrated in the intended malaria naive population. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0991-x) contains supplementary material, which is available to authorized users.
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Sousa JC, Milner E, Carroll D, McCalmont W, Gardner S, Moon J, Johnson JD, Lee P, Auschwitz J, Roncal N, Caridha D, Tungteung A, Zeng Q, Reyes S, Smith B, Li Q, Kozar MP, Melendez V, Dow G. The use of a prodrug approach to minimize potential CNS exposure of next generation quinoline methanols while maintaining efficacy in in vivo animal models. Eur J Drug Metab Pharmacokinet 2014; 39:231-6. [PMID: 24705994 DOI: 10.1007/s13318-013-0162-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Accepted: 12/04/2013] [Indexed: 11/25/2022]
Abstract
The use of mefloquine (MQ) for antimalarial treatment and prophylaxis has diminished largely in response to concerns about its neurologic side effects. An analog campaign designed to maintain the efficacy of MQ while minimizing blood-brain barrier (BBB) penetration has resulted in the synthesis of a prodrug with comparable-to-superior in vivo efficacy versus mefloquine in a P. berghei mouse model while exhibiting a sixfold reduction in CNS drug levels. The prodrug, WR319670, performed poorly compared to MQ in in vitro efficacy assays, but had promising in vitro permeability in an MDCK-MDR1 cell line BBB permeability screen. Its metabolite, WR308245, exhibited high predicted BBB penetration with excellent in vitro efficacy. Both WR319670 and WR308245 cured 5/5 animals in separate in vivo efficacy studies. The in vivo efficacy of WR319670 was thought to be due to the formation of a more active metabolite, specifically WR308245. This was supported by pharmacokinetics studies in non-infected mice, which showed that both IV and oral administration of WR319670 produced essentially identical levels of WR319670 and WR308245 in both plasma and brain samples at all time points. In these studies, the levels of WR308245 in the brain were 1/4 and 1/6 that of MQ in similar IV and oral studies, respectively. These data show that the use of WR319670 as an antimalarial prodrug was able to maintain efficacy in in vivo efficacy screens, while significantly lowering overall penetration of drug and metabolites across the BBB.
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Affiliation(s)
- Jason C Sousa
- Walter Reed Army Institute of Research, Silver Spring, MD, 20910, USA,
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Hastings IM, Hodel EM. Pharmacological considerations in the design of anti-malarial drug combination therapies - is matching half-lives enough? Malar J 2014; 13:62. [PMID: 24552440 PMCID: PMC3975950 DOI: 10.1186/1475-2875-13-62] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 02/15/2014] [Indexed: 11/20/2022] Open
Abstract
Anti-malarial drugs are now mainly deployed as combination therapy (CT), primarily as a mechanism to prevent or slow the spread of resistance. This strategy is justified by mathematical arguments that generally assume that drug 'resistance' is a binary all-or-nothing genetic trait. Herein, a pharmacological, rather than a purely genetic, approach is used to investigate resistance and it is argued that this provides additional insight into the design principles of anti-malarial CTs. It is usually suggested that half-lives of constituent drugs in a CT be matched: it appears more important that their post-treatment anti-malarial activity profiles be matched and strategies identified that may achieve this. In particular, the considerable variation in pharmacological parameters noted in both human and parasites populations may compromise this matching and it is, therefore, essential to accurately quantify the population pharmacokinetics of the drugs in the CTs. Increasing drug dosages will likely follow a law of diminishing returns in efficacy, i.e. a certain increase in dose will not necessarily lead to the same percent increase in efficacy. This may allow individual drug dosages to be lowered without proportional decrease in efficacy, reducing any potential toxicity, and allowing the other drug(s) in the CT to compensate for this reduced dosage; this is a dangerous strategy which is discussed further. Finally, pharmacokinetic and pharmacodynamic drug interactions and the role of resistance mechanisms are discussed. This approach generated an idealized target product profile (TPP) for anti-malarial CTs. There is a restricted pipeline of anti-malarial drugs but awareness of pharmacological design principles during the development stages could optimize CT design pre-deployment. This may help prevent changes in drug dosages and/or regimen that have previously occurred post-deployment in most current anti-malarial drugs.
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Affiliation(s)
- Ian M Hastings
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Eva Maria Hodel
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
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Dow GS, McCarthy WF, Reid M, Smith B, Tang D, Shanks GD. A retrospective analysis of the protective efficacy of tafenoquine and mefloquine as prophylactic anti-malarials in non-immune individuals during deployment to a malaria-endemic area. Malar J 2014; 13:49. [PMID: 24502679 PMCID: PMC3942710 DOI: 10.1186/1475-2875-13-49] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Accepted: 01/20/2014] [Indexed: 11/23/2022] Open
Abstract
Background In 2000/2001, the Australian Defense Forces (ADF), in collaboration with SmithKline Beecham and the United States Army, conducted a field trial to evaluate the safety, tolerability and efficacy of tafenoquine and mefloquine/primaquine for the prophylaxis of malaria amongst non-immune Australian soldiers deployed to East Timor (now called Timor Leste) for peacekeeping operations. The lack of a concurrent placebo control arm prevented an internal estimate of the malaria attack rate and so the protective efficacy of the study regimens was not determined at the time. Methods In a retrospective analysis of the trial results, the all species malaria attack rate was estimated for the prophylactic phase of the study which was defined as the period between administration of the first prophylactic dose and the first dose of post-deployment medication. First, the Plasmodium vivax attack rate was estimated during the prophylactic phase of the deployment by adjusting the observed P. vivax relapse rate during post-deployment to account for the known anti-relapse efficacies (or effectiveness) of the study medications (determined from prior studies). The all species malaria attack rate (P. vivax and Plasmodium falciparum) was then determined by adjusting the P. vivax attack rate based on the ratio of P. falciparum to P. vivax observed during prior ADF deployments to Timor Leste. This estimated all species malaria attack rate was then used as the ‘constant estimated attack rate’ in the calculation of the protective efficacy of tafenoquine and mefloquine during the prophylactic phase of the deployment. Results The estimated attack rate during the prophylactic phase of the study was determined to be 7.88%. The protective efficacies of tafenoquine and mefloquine, with corresponding 95% confidence intervals (95% CI), were determined to be 100% (93%-100%) and 100% (79%-100%) respectively. Conclusions The protective efficacy of tafenoquine (200 mg per day for three days, followed by weekly 200 mg maintenance doses) is similar to that of the weekly standard of care (mefloquine, 250 mg).
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Affiliation(s)
- Geoffrey S Dow
- United States Army Medical Materiel Development Activity, 1430 Veterans Drive, Fort Detrick, Maryland 21702, USA.
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The Curative and Prophylactic Effects of Xylopic Acid on Plasmodium berghei Infection in Mice. J Parasitol Res 2013; 2013:356107. [PMID: 23970953 PMCID: PMC3732589 DOI: 10.1155/2013/356107] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2013] [Revised: 05/29/2013] [Accepted: 06/14/2013] [Indexed: 11/17/2022] Open
Abstract
Efforts have been intensified to search for more effective antimalarial agents because of the observed failure of some artemisinin-based combination therapy (ACT) treatments of malaria in Ghana. Xylopic acid, a pure compound isolated from the fruits of the Xylopia aethiopica, was investigated to establish its attributable prophylactic, curative antimalarial, and antipyretic properties. The antimalarial properties were determined by employing xylopic acid (10-100 mg/kg) in ICR mice infected with Plasmodium berghei. Xylopic acid exerted significant (P < 0.05) effects on P. berghei infection similar to artemether/lumefantrine, the standard drug. Furthermore, it significantly (P < 0.05) reduced the lipopolysaccharide- (LPS-) induced fever in Sprague-Dawley rats similar to prednisolone. Xylopic acid therefore possesses prophylactic and curative antimalarial as well as antipyretic properties which makes it an ideal antimalarial agent.
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Dow GS, Gettayacamin M, Hansukjariya P, Imerbsin R, Komcharoen S, Sattabongkot J, Kyle D, Milhous W, Cozens S, Kenworthy D, Miller A, Veazey J, Ohrt C. Radical curative efficacy of tafenoquine combination regimens in Plasmodium cynomolgi-infected Rhesus monkeys (Macaca mulatta). Malar J 2011; 10:212. [PMID: 21801400 PMCID: PMC3161915 DOI: 10.1186/1475-2875-10-212] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2010] [Accepted: 07/29/2011] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Tafenoquine is an 8-aminoquinoline being developed for radical cure (blood and liver stage elimination) of Plasmodium vivax. During monotherapy treatment, the compound exhibits slow parasite and fever clearance times, and toxicity in glucose-6-phosphate dehydrogenase (G6PD) deficiency is a concern. Combination with other antimalarials may mitigate these concerns. METHODS In 2005, the radical curative efficacy of tafenoquine combinations was investigated in Plasmodium cynomolgi-infected naïve Indian-origin Rhesus monkeys. In the first cohort, groups of two monkeys were treated with a three-day regimen of tafenoquine at different doses alone and in combination with a three-day chloroquine regimen to determine the minimum curative dose (MCD). In the second cohort, the radical curative efficacy of a single-day regimen of tafenoquine-mefloquine was compared to that of two three-day regimens comprising tafenoquine at its MCD with chloroquine or artemether-lumefantrine in groups of six monkeys. In a final cohort, the efficacy of the MCD of tafenoquine against hypnozoites alone and in combination with chloroquine was investigated in groups of six monkeys after quinine pre-treatment to eliminate asexual parasites. Plasma tafenoquine, chloroquine and desethylchloroquine concentrations were determined by LC-MS in order to compare doses of the drugs to those used clinically in humans. RESULTS The total MCD of tafenoquine required in combination regimens for radical cure was ten-fold lower (1.8 mg/kg versus 18 mg/kg) than for monotherapy. This regimen (1.8 mg/kg) was equally efficacious as monotherapy or in combination with chloroquine after quinine pre-treatment to eliminate asexual stages. The same dose of (1.8 mg/kg) was radically curative in combination with artemether-lumefantrine. Tafenoquine was also radically curative when combined with mefloquine. The MCD of tafenoquine monotherapy for radical cure (18 mg/kg) appears to be biologically equivalent to a 600-1200 mg dose in humans. At its MCD in combination with blood schizonticidal drugs (1.8 mg/kg), the maximum observed plasma concentrations were substantially lower than (20-84 versus 550-1,100 ng/ml) after administration of 1, 200 mg in clinical studies. CONCLUSIONS Ten-fold lower clinical doses of tafenoquine than used in prior studies may be effective against P. vivax hypnozoites if the drug is deployed in combination with effective blood-schizonticidal drugs.
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Affiliation(s)
- Geoffrey S Dow
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, 503 Robert Grant Ave, Silver Spring, MD 20910, USA
| | - Montip Gettayacamin
- Department of Veterinary Medicine, United States Army Medical Component, Armed Forces Research Institute of Medical Sciences, 315/6, Rajthevi, Bangkok, 10400, Thailand
| | - Pranee Hansukjariya
- Department of Veterinary Medicine, United States Army Medical Component, Armed Forces Research Institute of Medical Sciences, 315/6, Rajthevi, Bangkok, 10400, Thailand
| | - Rawiwan Imerbsin
- Department of Veterinary Medicine, United States Army Medical Component, Armed Forces Research Institute of Medical Sciences, 315/6, Rajthevi, Bangkok, 10400, Thailand
| | - Srawuth Komcharoen
- Department of Veterinary Medicine, United States Army Medical Component, Armed Forces Research Institute of Medical Sciences, 315/6, Rajthevi, Bangkok, 10400, Thailand
| | - Jetsumon Sattabongkot
- Department of Entomology, United States Army Medical Component, Armed Forces Research Institute of Medical Sciences, 315/6, Rajthevi, Bangkok, 10400, Thailand
| | - Dennis Kyle
- College of Public Health, University of South Florida, 3720 Spectrum Blvd, FL 33612, USA
| | - Wilbur Milhous
- College of Public Health, University of South Florida, 3720 Spectrum Blvd, FL 33612, USA
| | - Simon Cozens
- GlaxoSmithKline R&D, Drug Metabolism and Pharmacokinetics, Park Road, Ware, Hertfordshire, SG12 0DP, UK
| | - David Kenworthy
- GlaxoSmithKline R&D, Drug Metabolism and Pharmacokinetics, Park Road, Ware, Hertfordshire, SG12 0DP, UK
| | - Anne Miller
- CPMS, QSi, GlaxoSmithKline, Mail Cose UW2431, 709 Swedeland Road, King of Prussia, PA, 19406, USA
| | - Jim Veazey
- US Army Medical Material Development Activity MCMR-UMP 1430 Veterans Drive Fort Detrick, MD 21702-9232, USA
| | - Colin Ohrt
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, 503 Robert Grant Ave, Silver Spring, MD 20910, USA
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Campo JJ, Whitman TJ, Freilich D, Burgess TH, Martin GJ, Doolan DL. Toward a surrogate marker of malaria exposure: modeling longitudinal antibody measurements under outbreak conditions. PLoS One 2011; 6:e21826. [PMID: 21818270 PMCID: PMC3144875 DOI: 10.1371/journal.pone.0021826] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Accepted: 06/13/2011] [Indexed: 11/22/2022] Open
Abstract
Background Biomarkers of exposure to Plasmodium falciparum would be a useful tool for the assessment of malaria burden and analysis of intervention and epidemiological studies. Antibodies to pre-erythrocytic antigens represent potential surrogates of exposure. Methods and Findings In an outbreak cohort of U.S. Marines deployed to Liberia, we modeled pre- and post-deployment IgG against P. falciparum sporozoites by immunofluorescence antibody test, and both IgG and IgM against the P. falciparum circumsporozoite protein by enzyme-linked immunosorbant assay. Modeling seroconversion thresholds by a fixed ratio, linear regression or nonlinear regression produced sensitivity for identification of exposed U.S. Marines between 58–70% and specificities between 87–97%, compared with malaria-naïve U.S. volunteers. Exposure was predicted in 30–45% of the cohort. Conclusion Each of the three models tested has merits in different studies, but further development and validation in endemic populations is required. Overall, these models provide support for an antibody-based surrogate marker of exposure to malaria.
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Affiliation(s)
- Joseph J. Campo
- Naval Medical Research Center, Silver Spring, Maryland, United States of America
- Barcelona Centre for International Health Research (CRESIB, Hospital Clínic-Universitat de Barcelona), Barcelona, Spain
- * E-mail: (JJC); (DLD)
| | - Timothy J. Whitman
- Infectious Diseases Department, National Naval Medical Center, Bethesda, Maryland, United States of America
| | - Daniel Freilich
- Naval Medical Research Center, Silver Spring, Maryland, United States of America
| | - Timothy H. Burgess
- Naval Medical Research Center, Silver Spring, Maryland, United States of America
- Infectious Diseases Department, National Naval Medical Center, Bethesda, Maryland, United States of America
| | - Gregory J. Martin
- Infectious Diseases Department, National Naval Medical Center, Bethesda, Maryland, United States of America
| | - Denise L. Doolan
- Naval Medical Research Center, Silver Spring, Maryland, United States of America
- Division of Immunology, Queensland Institute of Medical Research, Brisbane, Queensland, Australia
- School of Medicine, University of Queensland, Brisbane, Queensland, Australia
- * E-mail: (JJC); (DLD)
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14
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Characterization of in vivo metabolites of WR319691, a novel compound with activity against Plasmodium falciparum. Eur J Drug Metab Pharmacokinet 2011; 36:151-8. [DOI: 10.1007/s13318-011-0047-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Accepted: 06/06/2011] [Indexed: 11/27/2022]
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15
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Moon JE, Deye GA, Miller L, Fracisco S, Miller RS, Tosh D, Cummings JF, Ohrt C, Magill AJ. Plasmodium falciparum infection during suppressive prophylaxis with mefloquine does not induce an antibody response to merozoite surface protein-1(42). Am J Trop Med Hyg 2011; 84:825-9. [PMID: 21540397 DOI: 10.4269/ajtmh.2011.10-0699] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
A sensitive biomarker of malaria infection would obviate the need for placebo control arms in clinical trials of malaria prophylactic drugs. Antibodies to the 42-kDa fragment of merozoite surface protein-1 (MSP1(42)) have been identified as a potential marker of malaria exposure in individuals receiving prophylaxis with mefloquine. We conducted an open-label trial to determine the sensitivity of seroconversion to MSP1(42), defined as a fourfold rise in enzyme-linked immunosorbant assay (ELISA) titer, among 23 malaria naïve volunteers receiving mefloquine prophylaxis and 6 controls after Plasmodium falciparum sporozoite challenge. All members of the control cohort but none of the mefloquine cohort developed patent parasitemia. Four of six controls but zero of the mefloquine cohort seroconverted to MSP1(42). We conclude that malaria infection during suppressive prophylaxis does not induce antibody response to the blood-stage antigen MSP1(42) in a malaria-naïve study population.
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Affiliation(s)
- James E Moon
- Walter Reed Army Institute of Research, 503 Robert Grant Avenue, Silver Spring, MD 20910-7500, USA.
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16
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Dow GS, Milner E, Bathurst I, Bhonsle J, Caridha D, Gardner S, Gerena L, Kozar M, Lanteri C, Mannila A, McCalmont W, Moon J, Read KD, Norval S, Roncal N, Shackleford DM, Sousa J, Steuten J, White KL, Zeng Q, Charman SA. Central nervous system exposure of next generation quinoline methanols is reduced relative to mefloquine after intravenous dosing in mice. Malar J 2011; 10:150. [PMID: 21645370 PMCID: PMC3128011 DOI: 10.1186/1475-2875-10-150] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Accepted: 06/06/2011] [Indexed: 11/10/2022] Open
Abstract
Background The clinical use of mefloquine (MQ) has declined due to dose-related neurological events. Next generation quinoline methanols (NGQMs) that do not accumulate in the central nervous system (CNS) to the same extent may have utility. In this study, CNS levels of NGQMs relative to MQ were measured and an early lead chemotype was identified for further optimization. Experimental design The plasma and brain levels of MQ and twenty five, 4-position modified NGQMs were determined using LCMS/MS at 5 min, 1, 6 and 24 h after IV administration (5 mg/kg) to male FVB mice. Fraction unbound in brain tissue homogenate was assessed in vitro using equilibrium dialysis and this was then used to calculate brain-unbound concentration from the measured brain total concentration. A five-fold reduction CNS levels relative to mefloquine was considered acceptable. Additional pharmacological properties such as permeability and potency were determined. Results The maximum brain (whole/free) concentrations of MQ were 1807/4.9 ng/g. Maximum whole brain concentrations of NGQMs were 23 - 21546 ng/g. Maximum free brain concentrations were 0.5 to 267 ng/g. Seven (28%) and two (8%) compounds exhibited acceptable whole and free brain concentrations, respectively. Optimization of maximum free brain levels, IC90s (as a measure or potency) and residual plasma concentrations at 24 h (as a surrogate for half-life) in the same molecule may be feasible since they were not correlated. Diamine quinoline methanols were the most promising lead compounds. Conclusion Reduction of CNS levels of NGQMs relative to mefloquine may be feasible. Optimization of this property together with potency and long half-life may be feasible amongst diamine quinoline methanols.
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Affiliation(s)
- Geoffrey S Dow
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD, USA.
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17
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Yu D, Ding D, Jiang H, Stolzberg D, Salvi R. Mefloquine damage vestibular hair cells in organotypic cultures. Neurotox Res 2010; 20:51-8. [PMID: 20859773 DOI: 10.1007/s12640-010-9221-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Revised: 09/07/2010] [Accepted: 09/09/2010] [Indexed: 10/19/2022]
Abstract
Mefloquine is an effective and widely used anti-malarial drug; however, some clinical reports suggest that it can cause dizziness, balance, and vestibular disturbances. To determine if mefloquine might be toxic to the vestibular system, we applied mefloquine to organotypic cultures of the macula of the utricle from postnatal day 3 rats. The macula of the utricle was micro-dissected out as a flat surface preparation and cultured with 10, 50, 100, or 200 μM mefloquine for 24 h. Specimens were stained with TRITC-conjugated phalloidin to label the actin in hair cell stereocilia and TO-PRO-3 to visualize cell nuclei. Some utricles were also labeled with fluorogenic caspase-3, -8, or -9 indicators to evaluate the mechanism of programmed cell death. Mefloquine treatment caused a dose-dependent loss of utricular hair cells. Treatment with 10 μM caused a slight reduction, 50 μM caused a significant reduction, and 200 μM destroyed nearly all the hair cells. Hair cell nuclei in mefloquine-treated utricles were condensed and fragmented, morphological features of apoptosis. Mefloquine-treated utricles were positive for the extrinsic initiator caspase-8 and intrinsic initiator caspase-9 and downstream executioner caspase-3. These results indicate that mefloquine can induce significant hair cell degeneration in the postnatal rat utricle and that mefloquine-induced hair cell death is initiated by both caspase-8 and caspase-9.
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Affiliation(s)
- Dongzhen Yu
- Center for Hearing and Deafness, State University of New York at Buffalo, 137 Cary Hall, Buffalo, NY 14214, USA
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18
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Milner E, McCalmont W, Bhonsle J, Caridha D, Cobar J, Gardner S, Gerena L, Goodine D, Lanteri C, Melendez V, Roncal N, Sousa J, Wipf P, Dow GS. Anti-malarial activity of a non-piperidine library of next-generation quinoline methanols. Malar J 2010; 9:51. [PMID: 20149249 PMCID: PMC2833169 DOI: 10.1186/1475-2875-9-51] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Accepted: 02/11/2010] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND The clinical utility for mefloquine has been eroded due to its association with adverse neurological effects. Better-tolerated alternatives are required. The objective of the present study was the identification of lead compounds that are as effective as mefloquine, but exhibit physiochemical properties likely to render them less susceptible to passage across the blood-brain barrier. METHODS A library of drug-like non-piperidine analogs of mefloquine was synthesized. These compounds are diverse in structure and physiochemical properties. They were screened in appropriate in vitro assays and evaluated in terms of their potential as lead compounds. The correlation of specific structural attributes and physiochemical properties with activity was assessed. RESULTS The most potent analogs were low molecular weight unconjugated secondary amines with no heteroatoms in their side-chains. However, these compounds were more metabolically labile and permeable than mefloquine. In terms of physiochemical properties, lower polar surface area, lower molecular weight, more freely rotatable bonds and fewer H-bond acceptors were associated with greater potency. There was no such relationship between activity and LogP, LogD or the number of hydrogen bond donors (HBDs). The addition of an H-bond donor to the side-chain yielded a series of active diamines, which were as metabolically stable as mefloquine but showed reduced permeability. CONCLUSIONS A drug-like library of non-piperidine analogs of mefloquine was synthesized. From amongst this library an active lead series of less permeable, but metabolically stable, diamines was identified.
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Affiliation(s)
- Erin Milner
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - William McCalmont
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Jayendra Bhonsle
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Diana Caridha
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Jose Cobar
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Sean Gardner
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Lucia Gerena
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Duane Goodine
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Charlotte Lanteri
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Victor Melendez
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Norma Roncal
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Jason Sousa
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Peter Wipf
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, USA
| | - Geoffrey Stuart Dow
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD, USA
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