Eliminating malaria transmission requires targeting immature and mature gametocytes through lipoidal uptake of antimalarials.

Novel antimalarial compounds targeting both the pathogenic and transmissible stages of the human malaria parasite, Plasmodium falciparum, would greatly benefit malaria elimination strategies. However, most compounds affecting asexual blood stage parasites show severely reduced activity against gametocytes. The impact of this activity loss on a compound's transmission-blocking activity is unclear.

Barcoded Asaia bacteria enable mosquito in vivo screens and identify novel systemic insecticides and inhibitors of malaria transmission.

This work addresses the need for new chemical matter in product development for control of pest insects and vector-borne diseases. We present a barcoding strategy that enables phenotypic screens of blood-feeding insects against small molecules in microtiter plate-based arrays and apply this to discovery of novel systemic insecticides and compounds that block malaria parasite development in the mosquito vector. Encoding of the blood meals was achieved through recombinant DNA-tagged Asaia bacteria that successfully colonised Aedes and Anopheles mosquitoes.

The antimalarial efficacy and mechanism of resistance of the novel chemotype DDD01034957.

New antimalarial therapeutics are needed to ensure that malaria cases continue to be driven down, as both emerging parasite resistance to frontline chemotherapies and mosquito resistance to current insecticides threaten control programmes. Plasmodium, the apicomplexan parasite responsible for malaria, causes disease pathology through repeated cycles of invasion and replication within host erythrocytes (the asexual cycle). Antimalarial drugs primarily target this cycle, seeking to reduce parasite burden within the host as fast as possible and to supress recrudescence for as long as possible.

A novel class of fast-acting antimalarial agents: Substituted 15-membered azalides.

Background And Purpose: Efficacy of current antimalarial treatments is declining as a result of increasing antimalarial drug resistance, so new and potent antimalarial drugs are urgently needed. Azithromycin, an azalide antibiotic, was found useful in malaria therapy, but its efficacy in humans is low.

Experimental Approach: Four compounds belonging to structurally different azalide classes were tested and their activities compared to azithromycin and chloroquine.

A high throughput screen for next-generation leads targeting malaria parasite transmission.

Spread of parasite resistance to artemisinin threatens current frontline antimalarial therapies, highlighting the need for new drugs with alternative modes of action. Since only 0.2-1% of asexual parasites differentiate into sexual, transmission-competent forms, targeting this natural bottleneck provides a tangible route to interrupt disease transmission and mitigate resistance selection.

Gametocytes from K13 Propeller Mutant Plasmodium falciparum Clinical Isolates Demonstrate Reduced Susceptibility to Dihydroartemisinin in the Male Gamete Exflagellation Inhibition Assay.

Mutations in the kelch propeller domain (K13 propeller) of parasites from Southeast Asia are associated with reduced susceptibility to artemisinin. We exposed -cultured stage V gametocytes from Cambodian K13 propeller mutant parasites to dihydroartemisinin and evaluated the inhibition of male gamete formation in an exflagellation inhibition assay (EIA). Gametocytes with the R539T and C580Y K13 propeller alleles were less susceptible to dihydroartemisinin and had significantly higher 50% inhibitory concentrations (ICs) than did gametocytes with wild-type alleles.

UCT943, a Next-Generation Plasmodium falciparum PI4K Inhibitor Preclinical Candidate for the Treatment of Malaria.

The 2-aminopyridine MMV048 was the first drug candidate inhibiting phosphatidylinositol 4-kinase (PI4K), a novel drug target for malaria, to enter clinical development. In an effort to identify the next generation of PI4K inhibitors, the series was optimized to improve properties such as solubility and antiplasmodial potency across the parasite life cycle, leading to the 2-aminopyrazine UCT943. The compound displayed higher asexual blood stage, transmission-blocking, and liver stage activities than MMV048 and was more potent against resistant and clinical isolates.

Synthesis and Structure-Activity Relationships of the Novel Antimalarials 5-Pyridinyl-4(1 H)-Pyridones.

Malaria is still one of the most prevalent parasitic infections in the world, with half of the world's population at risk for malaria. The effectiveness of current antimalarial therapies, even that of the most recent class of antimalarial drugs (artemisinin-combination therapies, ACTs), is under continuous threat by the spread of resistant Plasmodium strains. As a consequence, there is still an urgent requirement for new antimalarial drugs.

Potent Plasmodium falciparum gametocytocidal compounds identified by exploring the kinase inhibitor chemical space for dual active antimalarials.

Objectives: Novel chemical tools to eliminate malaria should ideally target both the asexual parasites and transmissible gametocytes. Several imidazopyridazines (IMPs) and 2-aminopyridines (2-APs) have been described as potent antimalarial candidates targeting lipid kinases. However, these have not been extensively explored for stage-specific inhibition of gametocytes in Plasmodium falciparum parasites.

A tetraoxane-based antimalarial drug candidate that overcomes PfK13-C580Y dependent artemisinin resistance.

K13 gene mutations are a primary marker of artemisinin resistance in Plasmodium falciparum malaria that threatens the long-term clinical utility of artemisinin-based combination therapies, the cornerstone of modern day malaria treatment. Here we describe a multinational drug discovery programme that has delivered a synthetic tetraoxane-based molecule, E209, which meets key requirements of the Medicines for Malaria Venture drug candidate profiles. E209 has potent nanomolar inhibitory activity against multiple strains of P.

Hundreds of dual-stage antimalarial molecules discovered by a functional gametocyte screen.

Plasmodium falciparum stage V gametocytes are responsible for parasite transmission, and drugs targeting this stage are needed to support malaria elimination. We here screen the Tres Cantos Antimalarial Set (TCAMS) using the previously developed P. falciparum female gametocyte activation assay (Pf FGAA), which assesses stage V female gametocyte viability and functionality using Pfs25 expression.

A novel validated assay to support the discovery of new anti-malarial gametocytocidal agents.

Background: Drugs that kill or inhibit Plasmodium gametocytes in the human host could potentially synergize the impact of other chemotherapeutic interventions by blocking transmission. To develop such agents, reliable methods are needed to study the in vitro activity of compounds against gametocytes. This study describes a novel assay for characterizing the activity of anti-malarial drugs against the later stages of Plasmodium falciparum gametocyte development using real-time PCR (qPCR).

Transmission-Blocking Potential of MEFAS, a Hybrid Compound Derived from Artesunate and Mefloquine.

Most antimalarial drugs target asexual parasites without reducing gametocyte formation or development. Drugs with dual roles, i.e.

A New Set of Chemical Starting Points with Plasmodium falciparum Transmission-Blocking Potential for Antimalarial Drug Discovery.

The discovery of new antimalarials with transmission blocking activity remains a key issue in efforts to control malaria and eventually eradicate the disease. Recently, high-throughput screening (HTS) assays have been successfully applied to Plasmodium falciparum asexual stages to screen millions of compounds, with the identification of thousands of new active molecules, some of which are already in clinical phases. The same approach has now been applied to identify compounds that are active against P.

Imaging-based high-throughput screening assay to identify new molecules with transmission-blocking potential against Plasmodium falciparum female gamete formation.

In response to a call for the global eradication of malaria, drug discovery has recently been extended to identify compounds that prevent the onward transmission of the parasite, which is mediated by Plasmodium falciparum stage V gametocytes. Lately, metabolic activity has been used in vitro as a surrogate for gametocyte viability; however, as gametocytes remain relatively quiescent at this stage, their ability to undergo onward development (gamete formation) may be a better measure of their functional viability. During gamete formation, female gametocytes undergo profound morphological changes and express translationally repressed mRNA.

Red blood cells derived from peripheral blood and bone marrow CD34⁺ human haematopoietic stem cells are permissive to Plasmodium parasites infection.

The production of fully functional human red cells in vitro from haematopoietic stem cells (hHSCs) has been successfully achieved. Recently, the use of hHSCs from cord blood represented a major improvement to develop the continuous culture system for Plasmodium vivax. Here, we demonstrated that CD34⁺ hHSCs from peripheral blood and bone marrow can be expanded and differentiated to reticulocytes using a novel stromal cell.

Male and female Plasmodium falciparum mature gametocytes show different responses to antimalarial drugs.

It is the mature gametocytes of Plasmodium that are solely responsible for parasite transmission from the mammalian host to the mosquito. They are therefore a logical target for transmission-blocking antimalarial interventions, which aim to break the cycle of reinfection and reduce the prevalence of malaria cases. Gametocytes, however, are not a homogeneous cell population.

Quinolone-3-diarylethers: a new class of antimalarial drug.

The goal for developing new antimalarial drugs is to find a molecule that can target multiple stages of the parasite's life cycle, thus impacting prevention, treatment, and transmission of the disease. The 4(1H)-quinolone-3-diarylethers are selective potent inhibitors of the parasite's mitochondrial cytochrome bc1 complex. These compounds are highly active against the human malaria parasites Plasmodium falciparum and Plasmodium vivax.

Exploration of 4(1H)-pyridones as a novel family of potent antimalarial inhibitors of the plasmodial cytochrome bc1.

A novel family of antimalarials based on the 4(1H)-pyridone scaffold is described. The compounds display potent antimalarial activity against Plasmodium falciparum in vitro and in vivo. Like atovaquone, 4(1H)-pyridones exert their antimalarial action by inhibiting selectively the electron-transport chain in P.

Comparison and Optimization of Different Methods for the In Vitro Production of Plasmodium falciparum Gametocytes.

The generation of sexually committed parasites (gametocytogenesis) is poorly understood in malaria. If the mechanisms regulating this process were elucidated, new opportunities for blocking malaria transmission could be revealed. Here we compare several methods described previously for the in vitro production of Plasmodium falciparum gametocytes.

Activity of clinically relevant antimalarial drugs on Plasmodium falciparum mature gametocytes in an ATP bioluminescence "transmission blocking" assay.

Background: Current anti-malarial drugs have been selected on the basis of their activity against the symptom-causing asexual blood stage of the parasite. Which of these drugs also target gametocytes, in the sexual stage responsible for disease transmission, remains unknown. Blocking transmission is one of the main strategies in the eradication agenda and requires the identification of new molecules that are active against gametocytes.

Design, synthesis, and in vitro activity of novel 2'-O-substituted 15-membered azalides.

Malaria remains one of the most widespread human infectious diseases, and its eradication will largely depend on antimalarial drug discovery. Here, we present a novel approach to the development of the azalide class of antimalarials by describing the design, synthesis, and characterization of novel 2'-O-substituted-9-deoxo-9a-methyl-9a-aza-9a-homoerythromycin A derivatives consisting of different quinoline moieties covalently liked to a 15-membered azalide scaffold at position 2'. By multistep straightforward synthesis, 19 new, stable, and soluble compounds were created and biologically profiled.

Novel hybrid molecules based on 15-membered azalide as potential antimalarial agents.

Malaria remains the most prevalent tropical disease, and due to the spread of resistant parasites novel therapeutics are urgently needed. Azithromycin has shown potential in malaria treatment so we designed hybrid azalide molecules with the aim to improve activity against and selectivity for the malaria parasite. Novel hybrid molecules comprising 4-aminoquinoline moiety covalently liked to 15-membered azalide scaffold at position C-3' were synthesized and biologically evaluated.

Cyclopropyl carboxamides, a chemically novel class of antimalarial agents identified in a phenotypic screen.

Malaria is one of the deadliest infectious diseases in the world, with the eukaryotic parasite Plasmodium falciparum causing the most severe form of the disease. Discovery of new classes of antimalarial drugs has become an urgent task to counteract the increasing problem of drug resistance. Screening directly for compounds able to inhibit parasite growth in vitro is one of the main approaches the malaria research community is now pursuing for the identification of novel antimalarial drug leads.