Changes in susceptibility of to antimalarial drugs in Uganda over time: 2019-2024.

Background: The treatment and control of malaria in Africa is challenged by drug resistance, including transporter, folate pathway, and PfK13 mutations that mediate resistance to aminoquinolines, antifolates, and artemisinins, respectively. Characterization of drug susceptibility informs optimal control strategies.

Methods: We characterized ex vivo susceptibilities to nine drugs of isolates collected from individuals presenting with uncomplicated falciparum malaria in eastern (2019-2024) and northern (2021-2024) Uganda using a growth inhibition assay and the dihydroartemisinin (DHA) ring survival assay (RSA).

susceptibilities to ganaplacide and diversity in potential resistance mediators in Ugandan isolates.

Novel antimalarials are urgently needed to combat rising resistance to available drugs. The imidazolopiperazine ganaplacide is a promising drug candidate, but decreased susceptibility of laboratory strains has been linked to polymorphisms in the cyclic amine resistance locus (PfCARL), acetyl-CoA transporter (PfACT), and UDP-galactose transporter (PfUGT). To characterize parasites causing disease in Africa, we assessed drug susceptibilities to ganaplacide in 750 .

Evolution of Partial Resistance to Artemisinins in Malaria Parasites in Uganda.

Background: Partial resistance of to the artemisinin component of artemisinin-based combination therapies, the most important malaria drugs, emerged in Southeast Asia and now threatens East Africa. Partial resistance, which manifests as delayed clearance after therapy, is mediated principally by mutations in the kelch protein K13 (PfK13). Limited longitudinal data are available on the emergence and spread of artemisinin resistance in Africa.

Susceptibility of Ugandan Plasmodium falciparum Isolates to the Antimalarial Drug Pipeline.

Malaria, especially Plasmodium falciparum infection, remains an enormous problem, and its treatment and control are seriously challenged by drug resistance. New antimalarial drugs are needed. To characterize the Medicines for Malaria Venture pipeline of antimalarials under development, we assessed the drug susceptibilities to 19 compounds targeting or potentially impacted by mutations in P.

Decreased susceptibility of Plasmodium falciparum to both dihydroartemisinin and lumefantrine in northern Uganda.

Artemisinin partial resistance may facilitate selection of Plasmodium falciparum resistant to combination therapy partner drugs. We evaluated 99 P. falciparum isolates collected in 2021 from northern Uganda, where resistance-associated PfK13 C469Y and A675V mutations have emerged, and eastern Uganda, where these mutations are uncommon.

Susceptibilities of Ugandan Plasmodium falciparum Isolates to Proteasome Inhibitors.

The proteasome is a promising target for antimalarial chemotherapy. We assessed susceptibilities of fresh Plasmodium falciparum isolates from eastern Uganda to seven proteasome inhibitors: two asparagine ethylenediamines, two macrocyclic peptides, and three peptide boronates; five had median IC values <100 nM. TDI8304, a macrocylic peptide lead compound with drug-like properties, had a median IC of 16 nM.

The Multistage Antimalarial Compound Calxinin Perturbates Ca Homeostasis by Targeting a Unique Ion Channel.

Malaria elimination urgently needs novel antimalarial therapies that transcend resistance, toxicity, and high costs. Our multicentric international collaborative team focuses on developing multistage antimalarials that exhibit novel mechanisms of action. Here, we describe the design, synthesis, and evaluation of a novel multistage antimalarial compound, 'Calxinin'.

Drug susceptibility of in eastern Uganda: a longitudinal phenotypic and genotypic study.

Background: Treatment and control of malaria depends on artemisinin-based combination therapies (ACTs) and is challenged by drug resistance, but thus far resistance to artemisinins and partner drugs has primarily occurred in southeast Asia. The aim of this study was to characterise antimalarial drug susceptibility of isolates from Tororo and Busia districts in Uganda.

Methods: In this prospective longitudinal study, isolates were collected from patients aged 6 months or older presenting at the Tororo District Hospital (Tororo district, a site with relatively low malaria incidence) or Masafu General Hospital (Busia district, a high-incidence site) in eastern Uganda with clinical symptoms of malaria, a positive Giemsa-stained blood film for , and no signs of severe disease.

Decreased Susceptibility to Dihydrofolate Reductase Inhibitors Associated With Genetic Polymorphisms in Ugandan Plasmodium falciparum Isolates.

Background: The Plasmodium falciparum dihydrofolate reductase (PfDHFR) inhibitors pyrimethamine and cycloguanil (the active metabolite of proguanil) have important roles in malaria chemoprevention, but drug resistance challenges their efficacies. A new compound, P218, was designed to overcome resistance, but drug-susceptibility data for P falciparum field isolates are limited.

Methods: We studied ex vivo PfDHFR inhibitor susceptibilities of 559 isolates from Tororo and Busia districts, Uganda, from 2016 to 2020, sequenced 383 isolates, and assessed associations between genotypes and drug-susceptibility phenotypes.

Associations between Varied Susceptibilities to PfATP4 Inhibitors and Genotypes in Ugandan Plasmodium falciparum Isolates.

Among novel compounds under recent investigation as potential new antimalarial drugs are three independently developed inhibitors of the Plasmodium falciparum P-type ATPase (PfATP4): KAE609 (cipargamin), PA92, and SJ733. We assessed susceptibilities to these compounds of 374 fresh P. falciparum isolates collected in Tororo and Busia districts, Uganda, from 2016 to 2019.

Balanced impacts of fitness and drug pressure on the evolution of PfMDR1 polymorphisms in Plasmodium falciparum.

Background: Anti-malarial drug resistance may be limited by decreased fitness in resistant parasites. Important contributors to resistance are mutations in the Plasmodium falciparum putative drug transporter PfMDR1.

Methods: Impacts on in vitro fitness of two common PfMDR1 polymorphisms, N86Y, which is associated with sensitivity to multiple drugs, and Y184F, which has no clear impact on drug sensitivity, were evaluated to study associations between resistance mediators and parasite fitness, measured as relative growth in competitive culture experiments.

Changing Prevalence of Potential Mediators of Aminoquinoline, Antifolate, and Artemisinin Resistance Across Uganda.

Background: In Uganda, artemether-lumefantrine is recommended for malaria treatment and sulfadoxine-pyrimethamine for chemoprevention during pregnancy, but drug resistance may limit efficacies.

Methods: Genetic polymorphisms associated with sensitivities to key drugs were characterized in samples collected from 16 sites across Uganda in 2018 and 2019 by ligase detection reaction fluorescent microsphere, molecular inversion probe, dideoxy sequencing, and quantitative polymerase chain reaction assays.

Results: Considering transporter polymorphisms associated with resistance to aminoquinolines, the prevalence of Plasmodium falciparum chloroquine resistance transporter (PfCRT) 76T decreased, but varied markedly between sites (0-46% in 2018; 0-23% in 2019); additional PfCRT polymorphisms and plasmepsin-2/3 amplifications associated elsewhere with resistance to piperaquine were not seen.

Antimalarial Trioxolanes with Superior Drug-Like Properties and In Vivo Efficacy.

The emergence of artemisinin resistance, combined with certain suboptimal properties of ozonide agents arterolane and artefenomel, has necessitated the search for new drug candidates in the endoperoxide class. Our group has focused on trioxolane analogues with substitution patterns not previously explored. Here, we describe the enantioselective synthesis of analogues bearing a -3″ carbamate side chain and find these to be superior, both in vitro and in vivo, to the previously reported amides.

Falcipain Inhibitors Based on the Natural Product Gallinamide A Are Potent in Vitro and in Vivo Antimalarials.

A library of analogues of the cyanobacterium-derived depsipeptide natural product gallinamide A were designed and prepared using a highly efficient and convergent synthetic route. Analogues were shown to exhibit potent inhibitory activity against the Plasmodium falciparum cysteine proteases falcipain 2 and falcipain 3 and against cultured chloroquine-sensitive (3D7) and chloroquine-resistant (W2) strains of P. falciparum.

Changing Molecular Markers of Antimalarial Drug Sensitivity across Uganda.

The potential spread of antimalarial drug resistance to Africa, in particular for artemisinins and key partner drugs, is a major concern. We surveyed genetic markers associated with drug sensitivity on 3 occasions at ∼6-month intervals in 2016 and 2017 at 10 sites representing a range of epidemiological settings in Uganda. For putative drug transporters, we found continued evolution toward wild-type sequences associated with increased sensitivity to chloroquine.

Modeling Prevention of Malaria and Selection of Drug Resistance with Different Dosing Schedules of Dihydroartemisinin-Piperaquine Preventive Therapy during Pregnancy in Uganda.

Dihydroartemisinin-piperaquine (DHA-PQ) is under study for intermittent preventive treatment during pregnancy (IPTp), but it may accelerate selection for drug resistance. Understanding the relationships between piperaquine concentration, prevention of parasitemia, and selection for decreased drug sensitivity can inform control policies and optimization of DHA-PQ dosing. Piperaquine concentrations, measures of parasitemia, and genotypes associated with decreased aminoquinoline sensitivity in Africa ( 86Y, 76T) were obtained from pregnant Ugandan women randomized to IPTp with sulfadoxine-pyrimethamine (SP) or DHA-PQ.

Impact of Intermittent Preventive Treatment During Pregnancy on Plasmodium falciparum Drug Resistance-Mediating Polymorphisms in Uganda.

Background: In a recent trial of intermittent preventive treatment in pregnancy (IPTp) in Uganda, dihydroartemisinin-piperaquine (DP) was superior to sulfadoxine-pyrimethamine (SP) in preventing maternal and placental malaria.

Methods: We compared genotypes using sequencing, fluorescent microsphere, and quantitative polymerase chain reaction assays at loci associated with drug resistance in Plasmodium falciparum isolated from subjects receiving DP or SP.

Results: Considering aminoquinoline resistance, DP was associated with increased prevalences of mutations at pfmdr1 N86Y, pfmdr1 Y184F, and pfcrt K76T compared to SP (64.

Altered Plasmodium falciparum Sensitivity to the Antiretroviral Protease Inhibitor Lopinavir Associated with Polymorphisms in pfmdr1.

The HIV protease inhibitor lopinavir inhibits Plasmodium falciparum aspartic proteases (plasmepsins) and parasite development, and children receiving lopinavir-ritonavir experienced fewer episodes of malaria than those receiving other antiretroviral regimens. Resistance to lopinavir was selected in vitro over ∼9 months, with ∼4-fold decreased sensitivity. Whole-genome sequencing of resistant parasites showed a mutation and increased copy number in pfmdr1 and a mutation in a protein of unknown function, but no polymorphisms in plasmepsin genes.

Intermittent Preventive Treatment with Dihydroartemisinin-Piperaquine in Ugandan Schoolchildren Selects for Plasmodium falciparum Transporter Polymorphisms That Modify Drug Sensitivity.

Dihydroartemisinin-piperaquine (DP) offers prolonged protection against malaria, but its impact on Plasmodium falciparum drug sensitivity is uncertain. In a trial of intermittent preventive treatment in schoolchildren in Tororo, Uganda, in 2011 to 2012, monthly DP for 1 year decreased the incidence of malaria by 96% compared to placebo; DP once per school term offered protection primarily during the first month after therapy. To assess the impact of DP on selection of drug resistance, we compared the prevalence of key polymorphisms in isolates that emerged at different intervals after treatment with DP.

Antimalarial Benzoxaboroles Target Plasmodium falciparum Leucyl-tRNA Synthetase.

There is a need for new antimalarials, ideally with novel mechanisms of action. Benzoxaboroles have been shown to be active against bacteria, fungi, and trypanosomes. Therefore, we investigated the antimalarial activity and mechanism of action of 3-aminomethyl benzoxaboroles against Plasmodium falciparum Two 3-aminomethyl compounds, AN6426 and AN8432, demonstrated good potency against cultured multidrug-resistant (W2 strain) P.

Extracts from L. and L. (Annonaceae) Potently and Selectively Inhibit .

The aim of this work was to screen extracts from and against . Crude ethanolic extracts, methylene chloride fractions, aqueous fractions, subfractions and isolated compounds (stigmasterol-3--β-d-glucopyranoside, lichexanthone, gallic acid and β-sitosterol-3--β-d-glucopyranoside) were tested for cytotoxicity on erythrocytes and Human Foreskin Fibroblasts cells and against the W2 strain of in culture. Results indicated that none of the extracts was cytotoxic at concentrations up to 10 µg/mL.

Impact of antimalarial treatment and chemoprevention on the drug sensitivity of malaria parasites isolated from ugandan children.

Changing treatment practices may be selecting for changes in the drug sensitivity of malaria parasites. We characterized ex vivo drug sensitivity and parasite polymorphisms associated with sensitivity in 459 Plasmodium falciparum samples obtained from subjects enrolled in two clinical trials in Tororo, Uganda, from 2010 to 2013. Sensitivities to chloroquine and monodesethylamodiaquine varied widely; sensitivities to quinine, dihydroartemisinin, lumefantrine, and piperaquine were generally good.

Synthesis of gallinamide A analogues as potent falcipain inhibitors and antimalarials.

Analogues of the natural product gallinamide A were prepared to elucidate novel inhibitors of the falcipain cysteine proteases. Analogues exhibited potent inhibition of falcipain-2 (FP-2) and falcipain-3 (FP-3) and of the development of Plasmodium falciparum in vitro. Several compounds were equipotent to chloroquine as inhibitors of the 3D7 strain of P.