Project description:The increasing spread of drug-resistant malaria strains underscores the need for new antimalarial agents with novel modes of action (MOAs). Here, we describe a compound representative of a new class of antimalarials. This molecule, ACT-213615, potently inhibits in vitro erythrocytic growth of all tested Plasmodium falciparum strains, irrespective of their drug resistance properties, with IC(50) values in the low single-digit nanomolar range. Like the clinically used artemisinins, the compound equally and very rapidly affects all three asexual erythrocytic parasite stages. In contrast, microarray studies suggest that the MOA of ACT-213615 is different from that of the artemisinins and other known antimalarials. ACT-213615 is orally bioavailable in mice, exhibits activity in the murine P. berghei model and efficacy comparable to that of the reference drug chloroquine in the recently established P. falciparum SCID mouse model.ACT-213615 represents a new class of potent antimalarials that merits further investigation for its clinical potential. Histone deacetylase (HDACs) inhibitors are being intensively pursued as potential new antimalarial drugs, and are also emerging as valuable tools for investigating transcriptional control in malaria parasites. In this study, the genome-wide transcriptional effects of three structurally related hydroxamate HDAC inhibitors were profiled in Plasmodium falciparum, the most lethal of the malaria parasite species that infects humans. Trophozoite-stage P. falciparum cells were treated with ACT-213615 for increasing amount of time at IC50 concentration and cells were harvested in parralled with DMSO treated controls for microarray-based transcriptional profiling.
Project description:The increasing spread of drug-resistant malaria strains underscores the need for new antimalarial agents with novel modes of action (MOAs). Here, we describe a compound representative of a new class of antimalarials. This molecule, ACT-213615, potently inhibits in vitro erythrocytic growth of all tested Plasmodium falciparum strains, irrespective of their drug resistance properties, with IC(50) values in the low single-digit nanomolar range. Like the clinically used artemisinins, the compound equally and very rapidly affects all three asexual erythrocytic parasite stages. In contrast, microarray studies suggest that the MOA of ACT-213615 is different from that of the artemisinins and other known antimalarials. ACT-213615 is orally bioavailable in mice, exhibits activity in the murine P. berghei model and efficacy comparable to that of the reference drug chloroquine in the recently established P. falciparum SCID mouse model.ACT-213615 represents a new class of potent antimalarials that merits further investigation for its clinical potential. Histone deacetylase (HDACs) inhibitors are being intensively pursued as potential new antimalarial drugs, and are also emerging as valuable tools for investigating transcriptional control in malaria parasites. In this study, the genome-wide transcriptional effects of three structurally related hydroxamate HDAC inhibitors were profiled in Plasmodium falciparum, the most lethal of the malaria parasite species that infects humans.
Project description:Plasmodium falciparum causes the most lethal form of malaria. The frontline treatments for this severe disease are combination therapies based on semisynthetic peroxide antimalarials, known as artemisinins. There is growing resistance to artemisinins and new drugs with novel mechanisms of action are urgently required. Synthetic peroxide antimalarials, known as ozonides, exhibit potent antimalarial activity both in vitro and in vivo. Here, we used chemical proteomics to investigate the protein alkylation targets of clickable artemisinin and ozonide probes, including an analogue of the ozonide clinical candidate, OZ439. We greatly expanded the list of protein targets for peroxide antimalarials and identified redox processes as being significantly enriched from the list of protein targets for both artemisinins and ozonides. Disrupted redox homeostasis was confirmed with the use of a genetically encoded fluorescence-based biosensor comprising a redox-sensitive GFP (roGFP) fused to human glutaredoxin 1. This facilitated specific and dynamic live imaging of the glutathione redox potential in the cytosol of peroxide-treated infected red blood cells with high sensitivity and temporal resolution. We also used a targeted LC-MS based thiol metabolomics assay to accurately measure relative changes in cellular thiol levels (including thiol metabolites, glutathione precursors and oxidised and reduced glutathione) within peroxide-treated P. falciparum-infected red blood cells. This work shows that peroxide antimalarials disproportionately alkylate proteins involved in redox homeostasis and that disrupted redox processes are involved in the mechanism of action of these important antimalarials.
Project description:Drug resistance to nearly all antimalarials following their rollout underscores the need for novel chemotypes with novel mode of action to replenish the antimalarial drug-development pipeline. We identified a novel class of compounds in the antimalarial armory. Compound 31, characterized by a hydroxybenzamide scaffold, displays potent activity against blood-stage and late sexual stages of Plasmodium falciparum and no toxicity in human cells. Resistance selection studies with 31 identified a novel point mutation in the P. falciparum multidrug-resistance protein 1 (pfmdr1) gene, which was confirmed by CRISPR/Cas9-based gene editing as the primary mediator of resistance. Despite this, no cross-resistance towards first-line antimalarials were identified. Proteomics studies indicated that the primary mode of action of 31 is through direct binding to cytosolic ribosomal subunits, thereby inhibiting protein synthesis in the parasite. Taken together, compound 31 is a promising starting point for the development of a next-generation antimalarial.
Project description:Optimize SNP genotyping probes and demonstrate a new P. falciparum microarray platform that includes CGH and resequencing probes on the same chip
Project description:Transcriptional profiling of P. falciparum cultures treated with cyclohexylamine over time (18, 25 and 30 hours post invasion) A control experiment was also set up in which P. falciparum was not treated with cyclohexylamine, and samples were taken at 18, 25 and 30 h post invasion). Background Plasmodium falciparum, the causative agent of severe human malaria, has evolved to become resistant to previously successful antimalarial chemotherapies, most notably chloroquine and the antifolates. The prevalence of resistant strains has necessitated the discovery and development of new chemical entities with novel modes-of-action. Although much effort has been invested in the creation of analogues based on existing drugs and the screening of chemical and natural compound libraries, a crucial shortcoming in current Plasmodial drug discovery efforts remains the lack of an extensive set of novel, validated drug targets. A requirement of these targets (or the pathways in which they function) is that they prove essential for parasite survival. The polyamine biosynthetic pathway, responsible for the metabolism of highly abundant amines crucial for parasite growth, proliferation and differentiation, is currently under investigation as an antimalarial target. Chemotherapeutic strategies targeting this pathway have been successfully utilized for the treatment of Trypanosomes causing West African sleeping sickness. In order to further evaluate polyamine depletion as possible antimalarial intervention, the consequences of inhibiting P. falciparum spermidine synthase (PfSpdSyn) were examined on a morphological, transcriptomic, proteomic and metabolic level. Results Morphological analysis of P. falciparum 3D7 following application of the PfSpdSyn inhibitor cyclohexylamine confirmed that parasite development was completely arrested at the early trophozoite stage. This is in contrast to untreated parasites which progressed to late trophozoites at comparable time points. Global gene expression analyses confirmed a transcriptional arrest in the parasite. Several of the differentially expressed genes mapped to the polyamine biosynthetic and associated metabolic pathways. Differential expression of corresponding parasite proteins involved in polyamine biosynthesis was also observed. Most notably, uridine phosphorylase, adenosine deaminase, lysine decarboxylase (LDC) and S-adenosylmethionine synthetase were differentially expressed at the transcript and/or protein level. Several genes in associated metabolic pathways (purine metabolism and various methyltransferases) were also affected. The specific nature of the perturbation was additionally reflected by changes in polyamine metabolite levels. Conclusions This study details the malaria parasite’s response to PfSpdSyn inhibition on the transcriptomic, proteomic and metabolic levels. The results corroborate and significantly expand previous functional genomics studies relating to polyamine depletion in this parasite. Moreover, they confirm the role of transcriptional regulation in P. falciparum, particularly in this pathway. The findings promote this essential pathway as a target for antimalarial chemotherapeutic intervention strategies. Keywords: Time course experiment in response to a drug treatment
Project description:The objective of this study is to characterize gene expression signatures associated with in vivo artemisinin resistance phenotype and its transcriptional response to Artemisinin Combination Therapy (ACT) treatment . RNA-seq was applied to establish the global gene expression profiles for 196 and 180 isolates sampled from patients prior to and post to ACT treatment.