Malaria is a preventable and treatable disease, but to this date it causes considerable threat to individuals in tropical regions. Difficulties in managing malaria are associated with emerging resistance to antimalarial drugs in current usage. The World Health Organisation currently recommends the artemisinin-based combination therapies (ACTs) as frontline treatment for uncomplicated Plasmodium falciparum malaria in all endemic areas. However, the emergence of artemisinin resistant parasites threatens regional malaria control and elimination goals. Therefore there is a desperate need for the generation of novel antimalarials with unique modes of action to combat this devastating disease. Novel triazine compounds have been discovered with low nanomolar activity against P. falciparum parasites and low toxicity, offering a promising starting point for new drug discovery. However, the precise mode of action of triazines is currently unknown. This study investigated the mode of action of triazine antimalarial compounds using untargeted and targeted metabolomics.
LC-MS based untargeted metabolomics analysis revealed the triazine compounds to have some similarities to clinically-used quinoline drugs. In particular, the triazines, chloroquine and piperaquine specifically induced increased levels of dimethyl-arginine (DMA) compared to untreated controls. Furthermore, DMA accumulation was not observed with other antimalarials such as artemisinins or atovaquone.
DMA metabolism has not been thoroughly investigated in P. falciparum, but two isomers of DMA (symmetric and asymmetric) are known to exist in other organisms, and ADMA is a toxic metabolite. To further probe the changes in DMA levels following drug treatment, a targeted LC-MS method was developed to quantitatively measure ADMA and SDMA, and determine whether the ratio of SDMA:ADMA isomers is associated with the mechanism of action of triazine and quinoline antimalarials.