Atovaquone resistance in malaria parasites

Vaidya, Akhil B.; Mather, Michael W.

doi:10.1054/drup.2000.0157

Cited by 79 publications

(55 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…However, it is important to note that target identification is not absolutely necessary for the successful discovery and development of a new malaria drug. For example, atovaquone was originally thought to target dihydroorate dehydrogenase, but it actually targets a cytochrome (19), and the target of artemisinin is still not completely clear (11). However, target identification is an important step in any comprehensive development of antimalarial genomic studies.…”

Section: Discussionmentioning

confidence: 99%

“…To perform the secondary dosedown screen, we rescreened the 100 compound library plates identified to contain the 900 screening positives (19,968 total compounds) at ϳ5-fold-lower concentration than the primary screen. The compounds were dispensed using a Visio compound transfer robot equipped with a 20-nl 384-pin head array into 384-well microtiter plates containing 30 l of complete medium, resulting in a final compound concentration of approximately 6 M. Screening was performed in duplicate on P. falciparum strain 3D7 and MDR laboratory strains HB3 and Dd2 using the DAPI P. falciparum growth assay as described in Materials and Methods.…”

Section: Vol 51 2007 In Vitro Assay For Antimalarial-drug Discoverymentioning

confidence: 99%

See 1 more Smart Citation

High-Throughput Plasmodium falciparum Growth Assay for Malaria Drug Discovery

Baniecki

Wirth

Clardy

2007

Antimicrob Agents Chemother

151

144

View full text Add to dashboard Cite

New therapeutic agents for the treatment of malaria, the world's most deadly parasitic disease, are urgently needed. Malaria afflicts 300 to 500 million people and results in 1 to 2 million deaths annually, and more than 85% of all malaria-related mortality involves young children and pregnant women in sub-Saharan Africa. The emergence of multidrug-resistant parasites, especially in Plasmodium falciparum, has eroded the efficacy of almost all currently available therapeutic agents. The discovery of new drugs, including drugs with novel cellular targets, could be accelerated with a whole-organism high-throughput screen (HTS) of structurally diverse small-molecule libraries. The standard whole-organism screen is based on incorporation of [ 3 H]hypoxanthine and has liabilities, such as limited throughput, high cost, multiple labor-intensive steps, and disposal of radioactive waste. Recently, screens have been reported that do not use radioactive incorporation, but their reporter signal is not robust enough for HTS. We report a P. falciparum growth assay that is technically simple, robust, and compatible with the automation necessary for HTS. The assay monitors DNA content by addition of the fluorescent dye 4 ,6-diamidino-2-phenylindole (DAPI) as a reporter of blood-stage parasite growth. This DAPI P. falciparum growth assay was used to measure the 50% inhibitory concentrations (IC 50 s) of a diverse set of known antimalarials. The resultant IC 50 s compared favorably with those obtained in the [ 3 H]hypoxanthine incorporation assay. Over 79,000 small molecules have been tested for antiplasmodial activity using the DAPI P. falciparum growth assay, and 181 small molecules were identified as highly active against multidrug-resistant parasites.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Vol 51 2007 In Vitro Assay For Antimalarial-drug Discoverymentioning

confidence: 99%

High-Throughput Plasmodium falciparum Growth Assay for Malaria Drug Discovery

Baniecki

Wirth

Clardy

2007

Antimicrob Agents Chemother

151

144

View full text Add to dashboard Cite

show abstract

“…Although cyt bc 1 can be effectively inhibited at either its quinol oxidase (Q o ) or quinone reductase (Q i ) site, ATV is a selective Q o site inhibitor (14), and ATV resistance is associated with point mutations at this site, including the clinically relevant Y268S substitution that reduces sensitivity to ATV by more than 1,000-fold (15,16). Our group has recently shown that current preclinical candidate ELQ-300 potently inhibits the Q i site of cyt bc 1 rather than the Q o site exploited by ATV (17).…”

mentioning

confidence: 99%

Atovaquone and ELQ-300 Combination Therapy as a Novel Dual-Site Cytochrome bc ₁ Inhibition Strategy for Malaria

Stickles

Smilkstein

Morrisey

et al. 2016

Antimicrob Agents Chemother

View full text Add to dashboard Cite

cAntimalarial combination therapies play a crucial role in preventing the emergence of drug-resistant Plasmodium parasites. Although artemisinin-based combination therapies (ACTs) comprise the majority of these formulations, inhibitors of the mitochondrial cytochrome bc 1 complex (cyt bc 1 ) are among the few compounds that are effective for both acute antimalarial treatment and prophylaxis. There are two known sites for inhibition within cyt bc 1 : atovaquone (ATV) blocks the quinol oxidase (Q o ) site of cyt bc 1 , while some members of the endochin-like quinolone (ELQ) family, including preclinical candidate ELQ-300, inhibit the quinone reductase (Q i ) site and retain full potency against ATV-resistant Plasmodium falciparum strains with Q o site mutations. Here, we provide the first in vivo comparison of ATV, ELQ-300, and combination therapy consisting of ATV plus ELQ-300 (ATV:ELQ-300), using P. yoelii murine models of malaria. In our monotherapy assessments, we found that ATV functioned as a single-dose curative compound in suppressive tests whereas ELQ-300 demonstrated a unique cumulative dosing effect that successfully blocked recrudescence even in a high-parasitemia acute infection model. ATV:ELQ-300 therapy was highly synergistic, and the combination was curative with a single combined dose of 1 mg/kg of body weight. Compared to the ATV: proguanil (Malarone) formulation, ATV:ELQ-300 was more efficacious in multiday, acute infection models and was equally effective at blocking the emergence of ATV-resistant parasites. Ultimately, our data suggest that dual-site inhibition of cyt bc 1 is a valuable strategy for antimalarial combination therapy and that Q i site inhibitors such as ELQ-300 represent valuable partner drugs for the clinically successful Q o site inhibitor ATV.

show abstract

“…Unfortunately, high rates of recrudescent infection and treatment failure were seen after anti-malarial use of atovaquone alone [6], and treatment failures after atovaquone-proguanil combination therapy (Malarone®) were soon evident [7,8] despite only limited worldwide anti-malarial use. The rapid development and the diversity of atovaquone-resistant phenotypes and genotypes (perhaps a consequence of its mechanism of action [9]), the parallel evolution of resistance-encoding mutations [10] and their appearance with or without atovaquone exposure [11] in dispersed geographic locations, all indicate the strong propensity for atovaquone resistance. The hope that this risk can be overcome by appropriate combination therapy or by novel inhibitors continues to drive efforts to discover and develop cyt bc 1 inhibitor anti-malarials [12].…”

mentioning

confidence: 99%

A drug-selected Plasmodium falciparum lacking the need for conventional electron transport

Smilkstein

Forquer

Kanazawa

et al. 2008

Molecular and Biochemical Parasitology

View full text Add to dashboard Cite

Mitochondrial electron transport is essential for survival in Plasmodium falciparum, making the cytochrome (cyt) bc 1 complex an attractive target for antimalarial drug development. Here we report that P. falciparum cultivated in the presence of a novel cyt bc 1 inhibitor underwent a fundamental transformation in biochemistry to a phenotype lacking a requirement for electron transport through the cyt bc 1 complex. Growth of the drug-selected parasite clone (SB1-A6) is robust in the presence of diverse cyt bc 1 inhibitors, although electron transport is fully inhibited by these same agents. This transformation defies expected molecular-based concepts of drug resistance, has important implications for the study of cyt bc 1 as an antimalarial drug target, and may offer a glimpse into the evolutionary future of Plasmodium.Unlike most other eukaryotic cells, Plasmodia do not rely on mitochondrial electron transport for energy production. Nonetheless, inhibition of cyt bc 1 complex electron transport is normally lethal to the parasite, presumably by interruption of essential links to de novo pyrimidine biosynthesis, via dihydroorotate dehydrogenase (DHODH), and to maintenance of the mitochondrial membrane potential. Although these interrelationships determine the viability of the parasite and our ability to reduce that viability, they are only generally understood. Review of Plasmodial electron transport and cyt bc 1 complex function are beyond the scope of this report, but in-depth discussions are available [1][2][3].The anti-malarial drug atovaquone occupies the quinol oxidase (Q o ) site of mitochondrial cyt b, inhibiting electron flux through the cyt bc 1 complex (ubiquinol:cytochrome c oxidoreductase or complex III) and collapsing mitochondrial membrane potential with a potency 1000-fold greater in Plasmodium than mammalian cells [4,5]. Unfortunately, high rates of recrudescent infection and treatment failure were seen after anti-malarial use of atovaquone alone [6], and treatment failures after atovaquone-proguanil combination therapy (Malarone®) were soon evident [7,8] despite only limited worldwide anti-malarial use. The rapid development and the diversity of atovaquone-resistant phenotypes and genotypes (perhaps a consequence of its mechanism of action [9]), the parallel evolution of resistance-encoding mutations [10] and their appearance with or without atovaquone exposure [11] in dispersed geographic locations, all indicate the strong propensity for atovaquone resistance. The hope that this risk can be overcome by appropriate combination therapy or by novel inhibitors continues to drive efforts to discover and develop cyt bc 1 inhibitor anti-malarials [12].Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that ...

show abstract

Atovaquone resistance in malaria parasites

Cited by 79 publications

References 36 publications

High-Throughput Plasmodium falciparum Growth Assay for Malaria Drug Discovery

High-Throughput Plasmodium falciparum Growth Assay for Malaria Drug Discovery

Atovaquone and ELQ-300 Combination Therapy as a Novel Dual-Site Cytochrome bc ₁ Inhibition Strategy for Malaria

A drug-selected Plasmodium falciparum lacking the need for conventional electron transport

Contact Info

Product

Resources

About

Atovaquone resistance in malaria parasites

Cited by 79 publications

References 36 publications

High-Throughput Plasmodium falciparum Growth Assay for Malaria Drug Discovery

High-Throughput Plasmodium falciparum Growth Assay for Malaria Drug Discovery

Atovaquone and ELQ-300 Combination Therapy as a Novel Dual-Site Cytochrome bc 1 Inhibition Strategy for Malaria

A drug-selected Plasmodium falciparum lacking the need for conventional electron transport

Contact Info

Product

Resources

About

Atovaquone and ELQ-300 Combination Therapy as a Novel Dual-Site Cytochrome bc ₁ Inhibition Strategy for Malaria