title: Contrasting ex vivo efficacies of "reversed chloroquine" compounds in chloroquine-resistant Plasmodium falciparum and P. vivax isolates.
abstract: Chloroquine (CQ) has been the mainstay of malaria treatment for more than 60 years. However, the emergence and spread of CQ resistance now restrict its use to only a few areas where malaria is endemic. The aim of the present study was to investigate whether a novel combination of a CQ-like moiety and an imipramine-like pharmacophore can reverse CQ resistance ex vivo. Between March to October 2011 and January to September 2013, two "reversed chloroquine" (RCQ) compounds (PL69 and PL106) were tested against multidrug-resistant field isolates of Plasmodium falciparum (n = 41) and Plasmodium vivax (n = 45) in Papua, Indonesia, using a modified ex vivo schizont maturation assay. The RCQ compounds showed high efficacy against both CQ-resistant P. falciparum and P. vivax field isolates. For P. falciparum, the median 50% inhibitory concentrations (IC50s) were 23.2 nM for PL69 and 26.6 nM for PL106, compared to 79.4 nM for unmodified CQ (P < 0.001 and P = 0.036, respectively). The corresponding values for P. vivax were 19.0, 60.0, and 60.9 nM (P < 0.001 and P = 0.018, respectively). There was a significant correlation between IC50s of CQ and PL69 (Spearman's rank correlation coefficient [r s] = 0.727, P < 0.001) and PL106 (rs = 0.830, P < 0.001) in P. vivax but not in P. falciparum. Both RCQs were equally active against the ring and trophozoite stages of P. falciparum, but in P. vivax, PL69 and PL106 showed less potent activity against trophozoite stages (median IC50s, 130.2 and 172.5 nM) compared to ring stages (median IC50s, 17.6 and 91.3 nM). RCQ compounds have enhanced ex vivo activity against CQ-resistant clinical isolates of P. falciparum and P. vivax, suggesting the potential use of reversal agents in antimalarial drug development. Interspecies differences in RCQ compound activity may indicate differences in CQ pharmacokinetics between the two Plasmodium species.
authors.affiliation: Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Casuarina, Darwin, Australia.
authors.forename: Grennady
authors.initials: G
authors.lastname: Wirjanata
authors.affiliation: Eijkman Institute for Molecular Biology, Jakarta, Indonesia.
authors.forename: Boni F
authors.initials: BF
authors.lastname: Sebayang
authors.affiliation: Papuan Health and Community Development Foundation (PHCDF), Timika, Papua, Indonesia.
authors.forename: Ferryanto
authors.initials: F
authors.lastname: Chalfein
authors.affiliation: Papuan Health and Community Development Foundation (PHCDF), Timika, Papua, Indonesia.
authors.lastname: Prayoga
authors.affiliation: Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Casuarina, Darwin, Australia.
authors.forename: Irene
authors.initials: I
authors.lastname: Handayuni
authors.affiliation: Eijkman Institute for Molecular Biology, Jakarta, Indonesia.
authors.forename: Rintis
authors.initials: R
authors.lastname: Noviyanti
authors.affiliation: Papuan Health and Community Development Foundation (PHCDF), Timika, Papua, Indonesia District Health Authority, Timika, Papua, Indonesia.
authors.forename: Enny
authors.initials: E
authors.lastname: Kenangalem
authors.affiliation: Papuan Health and Community Development Foundation (PHCDF), Timika, Papua, Indonesia District Health Authority, Timika, Papua, Indonesia Department of Paediatrics, Faculty of Medicine, Gadjah Mada University, Yogyakarta, Indonesia.
authors.forename: Jeanne Rini
authors.initials: JR
authors.lastname: Poespoprodjo
authors.affiliation: Department of Chemistry, Portland State University, Portland, Oregon, USA DesignMedix, Inc., Portland, Oregon, USA.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Burgess
authors.affiliation: Department of Chemistry, Portland State University, Portland, Oregon, USA DesignMedix, Inc., Portland, Oregon, USA.
authors.forename: David H
authors.initials: DH
authors.lastname: Peyton
authors.affiliation: Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Casuarina, Darwin, Australia Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom.
authors.forename: Ric N
authors.initials: RN
authors.lastname: Price
authors.affiliation: Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Casuarina, Darwin, Australia jutta.marfurt@menzies.edu.au.
authors.forename: Jutta
authors.initials: J
authors.lastname: Marfurt
mesh_terms: D000962:Antimalarials / Q000494:pharmacology / Q000627:therapeutic use*; D002738:Chloroquine / Q000494:pharmacology / Q000627:therapeutic use*; D006801:Humans; D020128:Inhibitory Concentration 50; D008288:Malaria / Q000188:drug therapy; D008826:Microbial Sensitivity Tests; D010963:Plasmodium falciparum / Q000187:drug effects*; D010966:Plasmodium vivax / Q000187:drug effects*
chemical_list: D000962:Antimalarials; D002738:Chloroquine