ABSTRACT
We report a series of ß-branched acyclic tritylated deoxyuridine analogues as inhibitors of Plasmodium falciparum deoxyuridine-5'-triphosphate nucleotidohydrolase (PfdUTPase), an enzyme involved in nucleotide metabolism that acts as first line of defence against uracil incorporation into DNA. Compounds were assayed against both PfdUTPase and intact parasites showing a correlation between enzyme inhibition and cellular assays. ß-Branched acyclic uridine analogues described here showed equal or slightly better potency and selectivity compared with previously reported analogues. The best inhibitor gave a K(i) of 0.5 µM against PfdUTPase with selectivity greater than 200-fold compared to the corresponding human enzyme and sub-micromolar growth inhibition of P. falciparum (EC(50) 0.6 µM). A crystal structure of the complex of PfdUTPase with one of the inhibitors shows that this acyclic derivative binds to the active site in a similar manner to that previously reported for a tritylated cyclic deoxyuridine derivative.
Subject(s)
Antimalarials/pharmacology , Deoxyuridine/analogs & derivatives , Enzyme Inhibitors/pharmacology , Plasmodium falciparum/enzymology , Pyrophosphatases/antagonists & inhibitors , Antimalarials/chemistry , Deoxyuridine/chemistry , Deoxyuridine/pharmacology , Enzyme Inhibitors/chemistry , Humans , Models, Molecular , Structure-Activity RelationshipABSTRACT
The ubiquitous enzyme dUTP nucleotidohydrolase (dUTPase) catalyses the hydrolysis of dUTP to dUMP and can be considered as the first line of defence against incorporation of uracil into DNA. Inhibition of this enzyme results in over-incorporation of uracil into DNA, leading to DNA fragmentation and cell death and is therefore lethal. By taking advantage of structural differences between the human and Plasmodium dUTPase, selective inhibitors of the enzyme can be designed and synthesised with the aim of being developed into novel anti-parasitic drugs. Analogue based design was used to target the Plasmodium falciparum dUTPase (PfdUTPase). The structures of previously discovered selective inhibitors of the PfdUTPase were modified by insertion of an amide bond. A series of tritylated uracil acetamide derivatives were synthesised and assessed for inhibition of the enzyme and parasite growth in vitro. These compounds were weak inhibitors of the PfdUTPase.
