Progressing the global antimalarial portfolio: finding drugs which target multiple Plasmodium life stages

The number of novel antimalarial candidates entering preclinical development has seen an increase over the last several years. Most of these drug candidates were originally identified as hits coming from screening large chemical libraries specifically targeting the asexual blood stages of Plasmodium falciparum. Indeed, a large proportion of the current antimalarial arsenal has mainly targeted the asexual blood stage which is responsible for clinical symptoms of the disease. However, as part of the eradication agenda and to address resistance, any next-generation antimalarial should have additional activity on at least one other parasite life stage, i.e. gametocytocidal and/or tissue schizonticidal activity. We have applied this approach by screening compounds with intrinsic activity on asexual blood stages in assays against sexual and liver stages and identified two new antimalarial chemotypes with activity on multiple parasite life stages. This strategy can be expanded to identify other chemical classes of molecules with similar activity profiles for the next generation antimalarials. The following review summarizes the discovery of the spiroindolones and imidazolopiperazine classes of antimalarials developed by the NGBS consortium (Novartis Institute for Tropical Diseases, Genomic Institute of the Novartis Research Foundation, Biomedical Primate Research Center, and the Swiss Tropical and Public Health Institute) currently in clinical trials.