Title: A Comprehensive Review on Classifying Fast-acting and Slow-acting Antimalarial Agents Based on Time of Action and Target Organelle of Plasmodium sp

Transmission-Blocking Strategies for Malaria Eradication: Recent Advances in Small-Molecule Drug Development

Malaria drug research and development efforts have resurged in the last decade following the decelerating rate of mortality and malaria cases in endemic regions. The inefficiency of malaria interventions is largely driven by the spreading resistance of the Plasmodium falciparum parasite to current drug regimens and that of the malaria vector, the Anopheles mosquito, to insecticides. In response to the new eradication agenda, drugs that act by breaking the malaria transmission cycle (transmission-blocking drugs), which has been recognized as an important and additional target for intervention, are being developed. These drugs take advantage of the susceptibility of Plasmodium during population bottlenecks before transmission (gametocytes) and in the mosquito vector (gametes, zygotes, ookinetes, oocysts, sporozoites). To date, compounds targeting stage V gametocytes predominate in the chemical library of transmission-blocking drugs, and some of them have entered clinical trials. The targeting of Plasmodium mosquito stages has recently renewed interest in the development of innovative malaria control tools, which hold promise for the application of compounds effective at these stages. In this review, we highlight the major achievements and provide an update on the research of transmission-blocking drugs, with a particular focus on their chemical scaffolds, antiplasmodial activity, and transmission-blocking potential.

Identifying Fast and Slow-Acting Antimalarial Compounds of Pandemic Response Box Against Blood-Stage Culture of Plasmodium falciparum 3D7

The evolving clinical resistance in Plasmodium falciparum and the spike in malarial cases after the COVID-19 outbreak has triggered a search for new antimalarials effective against multi-drug-resistant P. falciparum strains. In this study, we assessed the timing of action, either fast or slow-acting of 13 potent compounds of Pandemic Response Box (PRB) against blood-stage Pf3D7 strain by SYBR Green-I assay. The asynchronous culture of Pf3D7 was exposed to varying concentrations of 13 compounds, and IC50 values were determined at 12, 24, 48, 72, and 96 h. We identified four fast-acting compounds (MMV000008, MMV1593541, MMV020752, MMV396785) with rapid-growth inhibitory activity having IC50 values ≤ 0.3 µM at 12 and 24 h. Similarly, we determined nine slow-acting compounds (MMV159340, MMV1634492, MMV1581558, MMV689758, MMV1593540, MMV394033, MMV019724, MMV000725, MMV1557856) having IC50 values ≤ 0.5 µM at 72 and 96 h. Furthermore, the stage-specific action of the two most potent fast-acting compounds (MMV1593541 and MMV020752) against rings, trophozoites, and schizonts at 48 h of exposure revealed that ring-stage parasites showed reduced IC50 values compared to mature stage forms. Therefore, our study demonstrates for the first time the identification of the most potent fast and slow-acting compounds from PRB against blood-stage infection, suggesting its utility in clinics and considering it as a partner drug in combination therapies.

Diarylpentanoids, the privileged scaffolds in antimalarial and anti-infectives drug discovery: A review

Asia is a hotspot for infectious diseases, including malaria, dengue fever, tuberculosis, and the pandemic COVID-19. Emerging infectious diseases have taken a heavy toll on public health and the economy and have been recognized as a major cause of morbidity and mortality, particularly in Southeast Asia. Infectious disease control is a major challenge, but many surveillance systems and control strategies have been developed and implemented. These include vector control, combination therapies, vaccine development, and the development of new anti-infectives. Numerous newly discovered agents with pharmacological anti-infective potential are being actively and extensively studied for their bioactivity, toxicity, selectivity, and mode of action, but many molecules lose their efficacy over time due to resistance developments. These facts justify the great importance of the search for new, effective, and safe anti-infectives. Diarylpentanoids, a curcumin derivative, have been developed as an alternative with better bioavailability and metabolism as a therapeutic agent. In this review, the mechanisms of action and potential targets of antimalarial drugs as well as the classes of antimalarial drugs are presented. The bioactivity of diarylpentanoids as a potential scaffold for a new class of anti-infectives and their structure-activity relationships are also discussed in detail.