Charman, S. A. | Search bioRxiv

bioRxiv2023

On-target, dual aminopeptidase inhibition provides cross-species antimalarial activity.

To combat the global burden of malaria, development of new drugs to replace or complement current therapies are urgently required. As drug resistance to existing treatments and clinical failures continue to rise, compounds targeting multiple life cycle stages and species need to be developed as a high priority. Here we show that the compound MMV1557817 is a nanomolar inhibitor of both Plasmodium falciparum and Plasmodium vivax aminopeptidases M1 and M17, leading to inhibition of end stage haemoglobin digestion in asexual parasites. Multi-stage analysis confirmed that MMV1557817 can also kill sexual stage P. falciparum, while cross-resistance studies confirmed the compound targets a mechanism of action distinct to current drug resistance mechanisms. Analysis of cross reactivity to homologous human enzymes shows the compound exhibits a high level of selectivity, whilst safety as well as druggability was confirmed in the murine model P. berghei. MMV1557817-resistant P. falciparum parasites displayed only low-level resistance (<3-fold) and exhibited a slow growth rate that was quickly outcompeted by wild type parasites. MMV1557817-resistant parasites digest significantly more haemoglobin and possess a mutation in PfA-M17 that induces partial destabilisation of the PfA-M17 homohexamer, resulting in high-level resistance to specific PfA-M17 inhibition, but enhanced sensitivity to specific PfA-M1 inhibition, and importantly, these parasites were highly sensitive to artemisinin. Overall, these results confirm MMV1557817 as a potential lead compound for further drug development and highlight the potential of dual inhibition of M1 and M17 as an effective multi-species drug targeting strategy.

microbiology↗

bioRxiv2020

System-wide biochemical analysis reveals ozonide antimalarials initially act by disrupting Plasmodium falciparum haemoglobin digestion

Ozonide antimalarials, OZ277 (arterolane) and OZ439 (artefenomel), are synthetic peroxide-based antimalarials with potent activity against the deadliest malaria parasite, Plasmodium falciparum. Here we used a "multi-omics" workflow, in combination with activity-based protein profiling (ABPP), to demonstrate that peroxide antimalarials initially target the haemoglobin (Hb) digestion pathway to kill malaria parasites. Time-dependent metabolomic profiling of ozonide-treated P. falciparum infected red blood cells revealed a rapid depletion of short Hb-derived peptides followed by subsequent alterations in lipid and nucleotide metabolism, while untargeted peptidomics showed accumulation of longer Hb-derived peptides. Quantitative proteomics and ABPP assays demonstrated that Hb-digesting proteases were increased in abundance and activity following treatment, respectively. The association between ozonide activity and Hb catabolism was also confirmed in a K13-mutant artemisinin resistant parasite line. To demonstrate that compromised Hb catabolism may be a primary mechanism involved in ozonide antimalarial activity, we showed that parasites forced to rely solely on Hb digestion for amino acids became hypersensitive to short ozonide exposures. Quantitative proteomics analysis also revealed parasite proteins involved in translation and the ubiquitin-proteasome system were enriched following drug treatment, suggestive of the parasite engaging a stress response to mitigate ozonide-induced damage. Taken together, these data point to a mechanism of action involving initial impairment of Hb catabolism, and indicate that the parasite regulates protein turnover to manage ozonide-induced damage. Author SummaryThe ozonides are a novel class of fully synthetic antimalarial drugs with potent activity against all parasite species that cause malaria, including the deadliest, Plasmodium falciparum. With the emergence of resistance to current frontline artemisinin-based antimalarials, new drugs are urgently needed and a clear understanding of their mechanism of action is essential so that they can be optimally deployed in the field. Here, we studied the biochemical effects of two ozonides, OZ277 (marketed in India in combination with piperaquine) and OZ439 (in Phase IIb clinical trials) in P. falciparum parasites using an untargeted multi-omics approach consisting of proteomics, peptidomics and time-dependent metabolomics, along with activity-based protease profiling. We found that the ozonides initially disrupt haemoglobin metabolism and that they likely engage the parasite proteostatic stress response. Furthermore, when the duration of ozonide exposure was extended beyond 3 hours to reflect clinically-relevant exposure periods, additional parasite biochemical pathways were perturbed. This comprehensive analysis provides new insight into the antimalarial mode of action of ozonides and provides new opportunities for interventions to enhance their antimalarial efficacy.

microbiology↗