Use of the NP-40 Detergent-Mediated Assay in Discovery of Inhibitors of β-Hematin Crystallization

Combrinck

Smith

et al. 2017

ACS Med. Chem. Lett.

In a previous study, target based screening was carried out for inhibitors of β-hematin (synthetic hemozoin) formation, and a series of triarylimidazoles were identified as active against Plasmodium falciparum. Here, we report the subsequent synthesis and testing of derivatives with varying substituents on the three phenyl rings for this series. The results indicated that a 2-hydroxy-1,3-dimethoxy substitution pattern on ring A is required for submicromolar parasite activity. In addition, cell-fractionation studies revealed uncommonly large, dose-dependent increases of P. falciparum intracellular exchangeable (free) heme, correlating with decreased parasite survival for β-hematin inhibiting derivatives.

mentioning

confidence: 94%

Identification and Mechanistic Evaluation of Hemozoin-Inhibiting Triarylimidazoles Active against Plasmodium falciparum

Combrinck

Smith

et al. 2017

ACS Med. Chem. Lett.

“…Detergent Mediated Assay for β-Haematin Inhibition The β-haematin formation inhibition assay method described by Carter et al 46,47) was modified for manual liquid delivery. Three stock solutions of the samples were prepared by dissolving the pre-weighed compound in DMSO and after sonication, diluting with DMSO to give 20 mM, 2 mM and 0.4 mM solutions of each sample.…”

Section: Pharmacologymentioning

confidence: 99%

“…The β-haematin formation inhibition assay method reported by Carter et al 32,33) was modified for manual liquid delivery as previously described. 34) The formation of haemozoin by P. falciparum, the details and relevance of which has been previously described, [34][35][36] is a suitable parasite-specific drug target for compounds able to cross the red blood cell membrane, the parasitophorous vacuole membrane, the P. falciparum plasma membrane and the acidic digestive vacuole (DV) membrane.…”

Section: Detergent Mediated Assay For β-Haematin Inhibitionmentioning

confidence: 99%

Synthesis and <i>in Vitro</i> Testing of Antimalarial Activity of Non-natural-Type Neocryptolepines: Structure–Activity Relationship Study of 2,11- and 9,11-Disubstituted 6-Methylindolo[2,3-<i>b</i>]quinolines

Wang

CHEMICAL & PHARMACEUTICAL BULLETIN

Wang

et al. 2013

This report describes the synthesis and in vitro anti-malarial evaluations of certain C2 or C8 and C11-disubstituted 6-methyl-5H-indolo[2,3-b]quinoline (neocryptolepine congener) derivatives. To attain higher activities, the structure-activity relationship (SAR) studies were conducted by varying the kind of alkylamino or ω-aminoalkylamino stubstituents at C11 and with Cl at the C2 position, or CO 2 Me at the C9 position. The anti-malarial activities of the tested compounds were significantly increased compared to the 11-non(alkylamino) derivatives. The 3-aminopropylamino group at C11 was further modified to urea and thiourea, which improved the cytotoxicity against normal cells. The best results were achieved with compounds 8 and 9d against the NF54 strain with the IC 50 /SI values as of 86 nM/20 and 317 nM/370, respectively. Furthermore, the compounds were tested for β-haematin inhibition. Twelve were found to have IC 50 values below 100 µM and a linear correlation between the β-haematin inhibition and cell growth inhibition in the NF54 strain was found for those derivatives with basic amino side chains. A second correlation was identified between the NF54 activity and physico-chemical factors related to solvation and polarity.

“…The β-hematin formation inhibition assay method described by Carter et al was modified for manual liquid delivery 38,39 . Two stock solutions of the samples were prepared by dissolving the pre-weighed compound in DMSO with sonication to give 20 mM and 2 mM solutions of each sample.…”

Section: β-Hematin Formation Inhibition Assaymentioning

confidence: 99%

Antimalarial benzoheterocyclic 4-aminoquinolines: Structure–activity relationship, in vivo evaluation, mechanistic and bioactivation studies

Ongarora

Strydom

Bioorganic & Medicinal Chemistry

et al. 2015

A novel class of benzoheterocyclic analogues of amodiaquine designed to avoid toxic reactive metabolite formation was synthesized and evaluated for antiplasmodial activity against K1 (multidrug resistant) and NF54 (sensitive) strains of the malaria parasite Plasmodium falciparum. Structure-activity relationship studies led to the identification of highly promising analogs, the most potent of which had IC50s in the nanomolar range against both strains. The compounds further demonstrated good in vitro microsomal metabolic stability while those subjected to in vivo pharmacokinetic studies had desirable pharmacokinetic profiles. In vivo antimalarial efficacy in Plasmodium berghei infected mice was evaluated for four compounds, all of which showed good activity following oral administration. In particular, compound 19 completely cured treated mice at a low multiple dose of 4×10 mg/kg. Mechanistic and bioactivation studies suggest hemozoin formation inhibition and a low likelihood of forming quinone-imine reactive metabolites, respectively. KEYWORDS: amodiaquine, benzoxazole, antiplasmodial activity, antimalarial activity, malaria, reactive metabolite, 4-aminoquinolines; bioactivation; structure-activity relationship; β-hematin; quinone imine. INTRODUCTIONMalaria remains a leading cause of morbidity and mortality globally. In 2012, there were an estimated 207 million cases of malaria and 627 000 deaths worldwide, with 90% of all malaria deaths occurring in sub-Saharan Africa. 1 One of the biggest challenges facing malaria chemotherapy is the rapid emergence of resistance to existing antimalarial drugs. 2 This challenge underscores the need for the continued search for new antimalarials.Chloroquine (1) (structure shown in Figure 1), was undoubtedly one of the most successful antimalarials ever owing to its good efficacy and low cost which made it affordable especially in the developing countries with high malaria endemicity. 3 Chloroquine was replaced as first line therapy by the sulfonamide antimalarials and, later on, artemisinin combination therapy (ACT), following the development of widespread resistance against the drug by Plasmodium falciparum. 4An aromatic side chain analogue of chloroquine, amodiaquine (2), however, retains activity against chloroquine-resistant Plasmodium strains. 5 Besides, it is an established fact that resistance against these 4-aminoquinolines is not a result of target modification but is caused by impaired accumulation of the drug at the target. 6,7 Consequently, amodiaquine is an attractive lead compound in the search for new antimalarials. Despite the desirable antimalarial efficacy of amodiaquine, chronic use especially during prophylaxis has been found to precipitate severe hepatotoxicity, myelotoxicity and agranulocytosis. 8,9 This toxicity has been attributed to the bioactivation of amodiaquine to reactive quinone imine (3) and aldehyde quinone imine (4) metabolites (figure 1) which covalently bind to cellular macromolecules causing drug-induced toxicity and cell damage di...