Oral Presentation 15th Lorne Infection and Immunity 2025

Uncovering the mechanism of action of novel antimalarials from the Janssen Jumpstarter library (#28)

Madeline G. Dans 1 2 , William Nguyen 1 2 , Coralie Boulet 3 , Jon Kyle Awalt 1 2 , Wenyin Su 1 2 , Anna Ngo 1 2 , Jocelyn Penington 1 2 , Cindy Evelyn 1 2 , Niall D. Geoghegan 1 2 , Kate E. Jarman 1 2 , Alexander G. Maier 1 2 , Giel G. van Dooren 4 , Tony Papenfuss 1 2 , Adele M. Lehane 4 , David F. Fidock 5 6 , Sergio Wittlin 7 8 , Stephen Brand 9 , Kym N. Lowes 1 2 , Kelly L. Rogers 1 2 , Paul R. Gilson 2 3 , Paul F. Jackson 10 , Alan F. Cowman 1 2 , Brad E. Sleebs 1 2
  1. The Walter and Eliza Hall Institute, Parkville, VIC, Australia
  2. The University of Melbourne, Parkville, VIC, Australia
  3. Burnet Institute, Melbourne, VIC, Australia
  4. Research School of Biology, The Australian National University, Canberra, ACT, Australia
  5. Department of Microbiology & Immunology , Columbia University, Irving Medical Center, New York, United States
  6. Center for Malaria Therapeutics and Antimicrobial Resistance, Division of Infectious Diseases, Department of Medicine, Columbia University, Irving Medical Center, New York, United States
  7. Swiss Tropical and Public Health Institute, Kreuzstrasse , Allschwil, Switzerland
  8. University of Basel, Basel, Switzerland
  9. Medicines for Malaria Venture, ICC, Route de Pré-Bois, Geneva, Switzerland
  10. Global Public Health, Janssen R&D LLC, La Jolla, California, United States

New classes of molecules to target Plasmodium falciparum are required to combat the spread of clinical resistance to current antimalarials. To discover new antimalarial chemotypes for development, we screened the Janssen Jumpstarter library of 80,000 drug-like compounds against asexual stage parasites using a lactate dehydrogenase (LDH) assay. Hit compounds were confirmed in a dose-response assay and a counterscreen and cytotoxic assays were carried out to further triage compounds. This culminated in a total of 85 hits from 8 novel compound classes.

We have conducted in-depth mechanism of action (MoA) studies to deconvolve the parasite targets of these 8 novel classes. We employed forward genetics to select resistant parasites against our hit compounds. By pairing this approach with whole genome sequencing, we identified genetic variants in our hit series revealing targets that include P. falciparum ATPase 4 (PfATP4), a StAR-related lipid transfer 1 protein (PfSTART1) and cytochrome bc1 complex (PfCytB). To validate these targets, we have conducted a series of phenotypic assays to assess Na+ efflux (PfATP4 inhibitor), live cell imaging (PfSTART1 inhibitor) and mitochondrion consumption (PfCytB inhibitor). Additionally, we have carried out profiling of our hits against clinically resistant parasites lines, demonstrating they remain susceptible to our novel chemotypes.

Complementing the MoA studies, we have also conducted extensive structure activity relationship studies on the novel hit classes to improve potency and selectivity against the parasite. Across all series, we achieved low nanomolar potency, comparable to that of current antimalarials in clinical use. We were able to achieve robust metabolic stability in three series with further improvement in aqueous stability being the next goal.

Overall, we have extensively characterised novel chemotypes against the malaria parasite that can be further developed into antimalarial compounds. Additionally, these compounds will serve as valuable biological tools for studying essential processes in the malaria parasite.