Journal of Antimicrobial Chemotherapy 2015-05-01

A combination of new screening assays for prioritization of transmission-blocking antimalarials reveals distinct dynamics of marketed and experimental drugs.

J M Bolscher, K M J Koolen, G J van Gemert, M G van de Vegte-Bolmer, T Bousema, D Leroy, R W Sauerwein, K J Dechering

Index: J. Antimicrob. Chemother. 70 , 1357-66, (2015)

Full Text: HTML

Abstract

The development of drugs to reduce malaria transmission is an important part of malaria eradication plans. We set out to develop and validate a combination of new screening assays for prioritization of transmission-blocking molecules.We developed high-throughput assays for screening compounds against gametocytes, the parasite stages responsible for onward transmission to mosquitoes. An existing gametocyte parasitic lactate dehydrogenase (pLDH) assay was adapted for use in 384-well plates, and a novel homogeneous immunoassay to monitor the functional transition of female gametocytes into gametes was developed. A collection of 48 marketed and experimental antimalarials was screened and subsequently tested for impact on sporogony in Anopheles mosquitoes, to directly quantify the transmission-blocking properties of antimalarials in relation to their effects on gametocyte pLDH activity or gametogenesis.The novel screening assays revealed distinct stage-specific kinetics and dynamics of drug effects. Peroxides showed the most potent transmission-blocking effects, with an intermediate speed of action and IC50 values that were 20-40-fold higher than the IC50s against the asexual stages causing clinical malaria. Finally, the novel synthetic peroxide OZ439 appeared to be a promising drug candidate as it exerted gametocytocidal and transmission-blocking effects at clinically relevant concentrations.© The Author 2015. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.