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

Celia Miguel-Blanco,María S Martínez-Martínez,Esperanza Herreros,Beatriz Díaz,Jake Baum,Michael J Delves,Gonzalo Colmenarejo,Laura De Las Heras,Esther Fernández,Robert E Sinden,Carolina González,Irene Molina,Sonia Lozano,Ana I Bardera,Sara Viera,Janneth Rodrigues,Andrea Ruecker

doi:10.1038/ncomms15160

Abstract

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. We identify over 400 compounds with activities <2 μM, chemically classified into 57 clusters and 33 singletons. Up to 68% of the hits are chemotypes described for the first time as late-stage gametocyte-targeting molecules. In addition, the biological profile of 90 compounds representing the chemical diversity is assessed. We confirm in vitro transmission-blocking activity of four of the six selected molecules belonging to three distinct scaffold clusters. Overall, this TCAMS gametocyte screen provides 276 promising antimalarial molecules with dual asexual/sexual activity, representing starting points for target identification and candidate selection.

Highlights

Plasmodium falciparum stage V gametocytes are responsible for parasite transmission, and drugs targeting this stage are needed to support malaria elimination
The P. falciparum female gametocyte activation assay (Pf FGAA) was the first to be scaled to 384-well format and validated for HTS28
To the best of our knowledge, this paper reports the largest screening effort performed to date using an assay that utilizes P. falciparum gamete formation as the endpoint

Summary

Introduction

Plasmodium falciparum stage V gametocytes are responsible for parasite transmission, and drugs targeting this stage are needed to support malaria elimination. Drugs with gametocytocidal activity have been detected using diverse readouts, such as metabolic parameters (ATP, pLDH, oxidoreduction)[17,18,19] or mitochondrial damage and luciferase reporters to track different gametocyte stages[20,21] Most of these assays are amenable to high throughput screening (HTS) of large compound libraries[20,22,23]. The 13.5 K compounds in the TCAMS are screened against stage V gametocytes in the Pf FGAA28 to identify molecules effective against female gamete formation As both female and male gametes are required for the development of mosquito stages, the parasite lifecycle may be interrupted by solely targeting one of them. The objective of this study is the discovery of new chemical diversity with activity against both asexual blood stages and stage V (female) gametocytes that may treat clinical symptoms and block malaria transmission

Objectives

Methods

Results

Conclusion