Adventures in poisoning parasites : chemical and biochemical investigations into the mode of action of novel anti-parasitic compounds against the kinetoplastid parasites

Abstract

A library series of analogues of the natural product fumagillin suitable for photoaffinity labelling were prepared by Rodrigo Pierre and subjected to photoaffinity labelling studies by Dr Tulloch and myself against Trypanosoma brucei. These identified Methionine aminopeptidase 2 and another, as yet unknown molecular target. Investigations were undertaken to validate if this target was 3-methylglutaconyl coenzyme A hydratase (3-MGCoA-H) as suggested by immobilised drug affinity chromatography. These investigations involved the generation of an overexpression cell line and the recombinant expression and purification of the protein. A series of N⁴-benzyl, N²-Phenyl quinazoline diamines were designed and synthesised to uncover structure activity relationships to inform the design of photoaffinity labelling probes. These compounds were found to be potent and selective in Leishmania major. A photoaffinity labelling probe and controls were designed and synthesised from the original SAR. Owing to a significant loss of potency against L. major, initial photoaffinity labelling studies were undertaken in Trypanosoma brucei, revealing several potential target proteins. A library of triphenylphosphonium and tributylphosphonium salts were assessed for their activity against Trypanosoma brucei, Trypanosoma cruzi and Leishmania major. A significant quantity of these compounds were found be potent or very potent against T. brucei and selective with respect to HeLa. The compounds were subjected to synergy studies and phenotypic screening of the KN morphologies and mitochondrial staining.