In VitroandIn VivoAntiplasmodial Activities of Risedronate and Its Interference with Protein Prenylation in Plasmodium falciparum

ABSTRACTThe increasing resistance of malarial parasites to almost all available drugs calls for the identification of new compounds and the detection of novel targets. Here, we establish the antimalarial activities of risedronate, one of the most potent bisphosphonates clinically used to treat bone resorption diseases, against blood stages ofPlasmodium falciparum(50% inhibitory concentration [IC50] of 20.3 ± 1.0 μM). We also suggest a mechanism of action for risedronate against the intraerythrocytic stage ofP. falciparumand show that protein prenylation seems to be modulated directly by this drug. Risedronate inhibits the transfer of the farnesyl pyrophosphate group to parasite proteins, an effect not observed for the transfer of geranylgeranyl pyrophosphate. Ourin vivoexperiments further demonstrate that risedronate leads to an 88.9% inhibition of the rodent parasitePlasmodium bergheiin mice on the seventh day of treatment; however, risedronate treatment did not result in a general increase of survival rates.

Download Full-text

Squalestatin Is an Inhibitor of Carotenoid Biosynthesis in Plasmodium falciparum

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.04500-14 ◽

2015 ◽

Vol 59 (6) ◽

pp. 3180-3188 ◽

Cited By ~ 10

Author(s):

Heloisa B. Gabriel ◽

Marcia F. Silva ◽

Emília A. Kimura ◽

Gerhard Wunderlich ◽

Alejandro M. Katzin ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Mammalian Cells ◽

Reverse Genetics ◽

Carotenoid Biosynthesis ◽

Content Type ◽

Key Enzyme ◽

Almost All ◽

New Compounds ◽

Inhibitor Of Carotenoid Biosynthesis

ABSTRACTThe increasing resistance of malaria parasites to almost all available drugs calls for the characterization of novel targets and the identification of new compounds. Carotenoids are polyisoprenoids from plants, algae, and some bacteria, and they are biosynthesized byPlasmodium falciparumbut not by mammalian cells. Biochemical and reverse genetics approaches were applied to demonstrate that phytoene synthase (PSY) is a key enzyme for carotenoid biosynthesis inP. falciparumand is essential for intraerythrocytic growth. The known PSY inhibitor squalestatin reduces biosynthesis of phytoene and kills parasites during the intraerythrocytic cycle. PSY-overexpressing parasites showed increased biosynthesis of phytoene and its derived product phytofluene and presented a squalestatin-resistant phenotype, suggesting that this enzyme is the primary target of action of this drug in the parasite.

Download Full-text

Effects of Tedizolid Phosphate on Survival Outcomes and Suppression of Production of Staphylococcal Toxins in a Rabbit Model of Methicillin-Resistant Staphylococcus aureus Necrotizing Pneumonia

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02734-16 ◽

2017 ◽

Vol 61 (4) ◽

Cited By ~ 6

Author(s):

Vien T. M. Le ◽

Hoan N. Le ◽

Marcos Gabriel Pinheiro ◽

Kenneth J. Hahn ◽

Mary L. Dinh ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Bacterial Production ◽

Protective Efficacy ◽

Survival Rates ◽

Rabbit Model ◽

Rank Test ◽

Necrotizing Pneumonia ◽

Time Curve ◽

Content Type

ABSTRACT The protective efficacy of tedizolid phosphate, a novel oxazolidinone that potently inhibits bacterial protein synthesis, was compared to those of linezolid, vancomycin, and saline in a rabbit model of Staphylococcus aureus necrotizing pneumonia. Tedizolid phosphate was administered to rabbits at 6 mg/kg of body weight intravenously twice daily, which yielded values of the 24-h area under the concentration-time curve approximating those found in humans. The overall survival rate was 83% for rabbits treated with 6 mg/kg tedizolid phosphate twice daily and 83% for those treated with 50 mg/kg linezolid thrice daily (P = 0.66 by the log-rank test versus the results obtained with tedizolid phosphate). These survival rates were significantly greater than the survival rates of 17% for rabbits treated with 30 mg/kg vancomycin twice daily (P = 0.003) and 17% for rabbits treated with saline (P = 0.002). The bacterial count in the lungs of rabbits treated with tedizolid phosphate was significantly decreased compared to that in the lungs of rabbits treated with saline, although it was not significantly different from that in the lungs of rabbits treated with vancomycin or linezolid. The in vivo bacterial production of alpha-toxin and Panton-Valentine leukocidin, two key S. aureus-secreted toxins that play critical roles in the pathogenesis of necrotizing pneumonia, in the lungs of rabbits treated with tedizolid phosphate and linezolid was significantly inhibited compared to that in the lungs of rabbits treated with vancomycin or saline. Taken together, these results indicate that tedizolid phosphate is superior to vancomycin for the treatment of S. aureus necrotizing pneumonia because it inhibits the bacterial production of lung-damaging toxins at the site of infection.

Download Full-text

In Vivo Efficacy and Pharmacokinetics of the 2-Aminomethylphenol Antimalarial JPC-3210 in the Aotus Monkey-Human Malaria Model

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01538-19 ◽

2019 ◽

Vol 64 (3) ◽

Author(s):

Fiona J. McCallum ◽

Geoffrey W. Birrell ◽

Marina Chavchich ◽

Ivor Harris ◽

Nicanor Obaldia ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Oral Dose ◽

In Vivo Efficacy ◽

Content Type ◽

Treatment And Prevention ◽

Elimination Half ◽

Long Acting ◽

Further Development ◽

Malaria Model

ABSTRACT Nonimmune Aotus monkeys infected with Plasmodium falciparum and Plasmodium vivax were cured of their infections when treated with a single oral dose of 5 mg/kg and 10 mg/kg of the 2-aminomethylphenol, JPC-3210, respectively. Corresponding mean blood elimination half-lives of JPC-3210 were lengthy at 19.1 days and 20.5 days, respectively. This in vivo potency and lengthy half-life supports the further development of JPC-3210 as a promising, long-acting blood schizontocidal antimalarial for malaria treatment and prevention.

Download Full-text

Computational Chemogenomics Drug Repositioning Strategy Enables the Discovery of Epirubicin as a New Repurposed Hit for Plasmodium falciparum and P. vivax

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02041-19 ◽

2020 ◽

Vol 64 (9) ◽

Author(s):

Letícia Tiburcio Ferreira ◽

Juliana Rodrigues ◽

Gustavo Capatti Cassiano ◽

Tatyana Almeida Tavella ◽

Kaira Cristina Peralis Tomaz ◽

...

Keyword(s):

Plasmodium Falciparum ◽

In Silico ◽

Antimalarial Activity ◽

Drug Repositioning ◽

Dna Gyrase ◽

Plasmodium Yoelii ◽

Computer Assisted ◽

Content Type

ABSTRACT Widespread resistance against antimalarial drugs thwarts current efforts for controlling the disease and urges the discovery of new effective treatments. Drug repositioning is increasingly becoming an attractive strategy since it can reduce costs, risks, and time-to-market. Herein, we have used this strategy to identify novel antimalarial hits. We used a comparative in silico chemogenomics approach to select Plasmodium falciparum and Plasmodium vivax proteins as potential drug targets and analyzed them using a computer-assisted drug repositioning pipeline to identify approved drugs with potential antimalarial activity. Among the seven drugs identified as promising antimalarial candidates, the anthracycline epirubicin was selected for further experimental validation. Epirubicin was shown to be potent in vitro against sensitive and multidrug-resistant P. falciparum strains and P. vivax field isolates in the nanomolar range, as well as being effective against an in vivo murine model of Plasmodium yoelii. Transmission-blocking activity was observed for epirubicin in vitro and in vivo. Finally, using yeast-based haploinsufficiency chemical genomic profiling, we aimed to get insights into the mechanism of action of epirubicin. Beyond the target predicted in silico (a DNA gyrase in the apicoplast), functional assays suggested a GlcNac-1-P-transferase (GPT) enzyme as a potential target. Docking calculations predicted the binding mode of epirubicin with DNA gyrase and GPT proteins. Epirubicin is originally an antitumoral agent and presents associated toxicity. However, its antiplasmodial activity against not only P. falciparum but also P. vivax in different stages of the parasite life cycle supports the use of this drug as a scaffold for hit-to-lead optimization in malaria drug discovery.

Download Full-text

A Single-Dose Combination Study with the Experimental Antimalarials Artefenomel and DSM265 To Determine Safety and Antimalarial Activity against Blood-Stage Plasmodium falciparum in Healthy Volunteers

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01371-19 ◽

2019 ◽

Vol 64 (1) ◽

Cited By ~ 2

Author(s):

James S. McCarthy ◽

Thomas Rückle ◽

Suzanne L. Elliott ◽

Emma Ballard ◽

Katharine A. Collins ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Antimalarial Activity ◽

Plasma Concentrations ◽

Parasite Clearance ◽

Blood Stage ◽

Content Type ◽

Dose Combination ◽

Combination Study ◽

Study Support ◽

New Compounds

ABSTRACT Artefenomel and DSM265 are two new compounds that have been shown to be well tolerated and effective when administered as monotherapy malaria treatment. This study aimed to determine the safety, pharmacokinetics, and pharmacodynamics of artefenomel and DSM265 administered in combination to healthy subjects in a volunteer infection study using the Plasmodium falciparum-induced blood-stage malaria model. Thirteen subjects were inoculated with parasite-infected erythrocytes on day 0 and received a single oral dose of artefenomel and DSM265 on day 7. Cohort 1 (n = 8) received 200 mg artefenomel plus 100 mg DSM265, and cohort 2 (n = 5) received 200 mg artefenomel plus 50 mg DSM265. Blood samples were collected to measure parasitemia, gametocytemia, and artefenomel-DSM265 plasma concentrations. There were no treatment-related adverse events. The pharmacokinetic profiles of artefenomel and DSM265 were similar to those of the compounds when administered as monotherapy, suggesting no pharmacokinetic interactions. A reduction in parasitemia occurred in all subjects following treatment (log10 parasite reduction ratios over 48 h [PRR48] of 2.80 for cohort 1 and 2.71 for cohort 2; parasite clearance half-lives of 5.17 h for cohort 1 and 5.33 h for cohort 2). Recrudescence occurred in 5/8 subjects in cohort 1 between days 19 and 28 and in 5/5 subjects in cohort 2 between days 15 and 22. Low-level gametocytemia (1 to 330 female gametocytes/ml) was detected in all subjects from day 14. The results of this single-dosing combination study support the further clinical development of the use of artefenomel and DSM265 in combination as a treatment for falciparum malaria. (This study has been registered at ClinicalTrials.gov under identifier NCT02389348.)

Download Full-text

Protein Prenylation and Hsp40 in Thermotolerance of Plasmodium falciparum Malaria Parasites

mBio ◽

10.1128/mbio.00760-21 ◽

2021 ◽

Author(s):

Emily S. Mathews ◽

Andrew J. Jezewski ◽

Audrey R. Odom John

Keyword(s):

Plasmodium Falciparum ◽

Life Cycle ◽

Heat Shock ◽

Heat Shock Protein ◽

Malaria Parasite ◽

Plasmodium Falciparum Malaria ◽

Complex Life Cycle ◽

Large Temperature ◽

Protein Prenylation ◽

Content Type

During its complex life cycle, the malaria parasite survives dramatic environmental stresses, including large temperature shifts. Protein prenylation is required during asexual replication of Plasmodium falciparum , and the canonical heat shock protein 40 protein (HSP40; PF3D7_1437900) is posttranslationally modified with a 15-carbon farnesyl isoprenyl group.

Download Full-text

Plasmodium falciparum K13 mutations in Africa and Asia present varying degrees of artemisinin resistance and an elevated fitness cost in African parasites

10.1101/2021.01.05.425445 ◽

2021 ◽

Author(s):

Barbara H. Stokes ◽

Kelly Rubiano ◽

Satish K. Dhingra ◽

Sachel Mok ◽

Judith Straimer ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Southeast Asia ◽

Survival Rates ◽

Point Mutations ◽

Artemisinin Resistance ◽

Parasite Clearance ◽

Definitive Evidence ◽

The Impact

AbstractThe emergence of artemisinin (ART) resistance in Plasmodium falciparum parasites has led to increasing rates of treatment failure with first-line ART-based combination therapies (ACTs) in Southeast Asia. In this region, select mutations in K13 can result in delayed parasite clearance rates in vivo and enhanced survival in the ring-stage survival assay (RSA) in vitro. Our genotyping of 3,299 P. falciparum isolates across 11 sub-Saharan countries reveals the continuing dominance of wild-type K13 and confirms the emergence of a K13 R561H variant in Rwanda. Using gene editing, we provide definitive evidence that this mutation, along with M579I and C580Y, can confer variable degrees of in vitro ART resistance in African P. falciparum strains. C580Y and M579I were both associated with substantial fitness costs in African parasites, which may counter-select against their dissemination in high-transmission settings. We also report the impact of multiple K13 mutations, including the predominant variant C580Y, on RSA survival rates and fitness in multiple Southeast Asian strains. No change in ART susceptibility was observed upon editing point mutations in ferrodoxin or mdr2, earlier associated with ART resistance in Southeast Asia. These data point to the lack of an evident biological barrier to mutant K13 mediating ART resistance in Africa, while identifying their detrimental impact on parasite growth.

Download Full-text

The Development of Novel Compounds Against Malaria: Quinolines, Triazolpyridines, Pyrazolopyridines and Pyrazolopyrimidines

Molecules ◽

10.3390/molecules24224095 ◽

2019 ◽

Vol 24 (22) ◽

pp. 4095 ◽

Cited By ~ 11

Author(s):

Luiz C. S. Pinheiro ◽

Lívia M. Feitosa ◽

Marilia O. Gandi ◽

Flávia F. Silveira ◽

Nubia Boechat

Keyword(s):

Plasmodium Falciparum ◽

Mouse Model ◽

Infected Mouse ◽

Plasmodium Berghei ◽

Medicinal Chemistry ◽

Quinoline Derivatives ◽

Dihydroorotate Dehydrogenase ◽

New Compounds

Based on medicinal chemistry tools, new compounds for malaria treatment were designed. The scaffolds of the drugs used to treat malaria, such as chloroquine, primaquine, amodiaquine, mefloquine and sulfadoxine, were used as inspiration. We demonstrated the importance of quinoline and non-quinoline derivatives in vitro with activity against the W2 chloroquine-resistant (CQR) Plasmodium falciparum clone strain and in vivo against Plasmodium berghei-infected mouse model. Among the quinoline derivatives, new hybrids between chloroquine and sulfadoxine were designed, which gave rise to an important prototype that was more active than both chloroquine and sulfadoxine. Hybrids between chloroquine–atorvastatin and primaquine–atorvastatin were also synthesized and shown to be more potent than the parent drugs alone. Additionally, among the quinoline derivatives, new mefloquine derivatives were synthesized. Among the non-quinoline derivatives, we obtained excellent results with the triazolopyrimidine nucleus, which gave us prototype I that inspired the synthesis of new heterocycles. The pyrazolopyrimidine derivatives stood out as non-quinoline derivatives that are potent inhibitors of the P. falciparum dihydroorotate dehydrogenase (PfDHODH) enzyme. We also examined the pyrazolopyridine and pyrazolopyrimidine nuclei.

Download Full-text

Synergistic Effect of Colistin Combined with PFK-158 against Colistin-Resistant Enterobacteriaceae

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00271-19 ◽

2019 ◽

Vol 63 (7) ◽

Cited By ~ 3

Author(s):

Youwen Zhang ◽

Xiukun Wang ◽

Xue Li ◽

Limin Dong ◽

Xinxin Hu ◽

...

Keyword(s):

Synergistic Effect ◽

Synergistic Effects ◽

Survival Rates ◽

New Combination ◽

Resistant Bacteria ◽

Content Type ◽

Checkerboard Assay ◽

High Level ◽

Time Kill

ABSTRACT As increasing numbers of colistin-resistant bacteria emerge, new therapies are urgently needed to treat infections caused by these pathogens. The discovery of new combination therapies is one important way to solve such problems. Here, we report that the antitumor drug PFK-158 and its analogs PFK-015 and 3PO can exert synergistic effects with colistin against colistin-resistant Enterobacteriaceae, including mcr-1-positive or high-level-colistin-resistant (HLCR) isolates, as shown by a checkerboard assay. The results of a time-kill assay revealed that colistin combined with PFK-158 continuously eliminated colistin-resistant Escherichia coli 13-43, Klebsiella pneumoniae H04, and Enterobacter cloacae D01 in 24 h. Images from scanning electron microscopy (SEM) at 5 h postinoculation confirmed the killing effect of the combination. Finally, in vivo treatment showed that PFK-158 had a better synergistic effect than its analogs. Compared to the corresponding rates after colistin monotherapy, the survival rates of systemically infected mice were significantly increased 30% or 60% when the mice received an intravenous injection of colistin in combination with 15 mg/kg of body weight PFK-158. These results have important implications for repurposing PFK-158 to combat colistin resistance.

Download Full-text

The Mu Subunit of Plasmodium falciparum Clathrin-Associated Adaptor Protein 2 ModulatesIn VitroParasite Response to Artemisinin and Quinine

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.04067-14 ◽

2015 ◽

Vol 59 (5) ◽

pp. 2540-2547 ◽

Cited By ~ 26

Author(s):

Gisela Henriques ◽

Donelly A. van Schalkwyk ◽

Rebekah Burrow ◽

David C. Warhurst ◽

Eloise Thompson ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Adaptor Protein ◽

Content Type ◽

Artemisinin Derivatives ◽

Combination Treatments ◽

Antimalarial Resistance ◽

Transgenic Parasites ◽

Multiple Drugs

ABSTRACTThe emergence of drug-resistant parasites is a serious threat faced by malaria control programs. Understanding the genetic basis of resistance is critical to the success of treatment and intervention strategies. A novel locus associated with antimalarial resistance,ap2-mu(encoding the mu chain of the adaptor protein 2 [AP2] complex), was recently identified in studies on the rodent malaria parasitePlasmodium chabaudi(pcap2-mu). Furthermore, analysis in Kenyan malaria patients of polymorphisms in thePlasmodium falciparumap2-muhomologue,pfap2-mu, found evidence that differences in the amino acid encoded by codon 160 are associated with enhanced parasite survivalin vivofollowing combination treatments which included artemisinin derivatives. Here, we characterize the role ofpfap2-muin mediating thein vitroantimalarial drug response ofP. falciparumby generating transgenic parasites constitutively expressing codon 160 encoding either the wild-type Ser (Ser160) or the Asn mutant (160Asn) form ofpfap2-mu. Transgenic parasites carrying thepfap2-mu160Asn allele were significantly less sensitive to dihydroartemisinin using a standard 48-hin vitrotest, providing direct evidence of an altered parasite response to artemisinin. Our data also provide evidence thatpfap2-muvariants can modulate parasite sensitivity to quinine. No evidence was found thatpfap2-muvariants contribute to the slow-clearance phenotype exhibited byP. falciparumin Cambodian patients treated with artesunate monotherapy. These findings provide compelling evidence thatpfap2-mucan modulateP. falciparumresponses to multiple drugs. We propose that this gene should be evaluated further as a potential molecular marker of antimalarial resistance.

Download Full-text