RESUMEN
Several of the enzymes related to the folate cycle are well-known for their role as clinically validated antimalarial targets. Nevertheless for serine hydroxymethyltransferase (SHMT), one of the key enzymes of this cycle, efficient inhibitors have not been described so far. On the basis of plant SHMT inhibitors from an herbicide optimization program, highly potent inhibitors of Plasmodium falciparum (Pf) and Plasmodium vivax (Pv) SHMT with a pyrazolopyran core structure were identified. Cocrystal structures of potent inhibitors with PvSHMT were solved at 2.6 Å resolution. These ligands showed activity (IC50/EC50 values) in the nanomolar range against purified PfSHMT, blood-stage Pf, and liver-stage P. berghei (Pb) cells and a high selectivity when assayed against mammalian cell lines. Pharmacokinetic limitations are the most plausible explanation for lack of significant activity of the inhibitors in the in vivo Pb mouse malaria model.
Asunto(s)
Antimaláricos/química , Antimaláricos/farmacología , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/farmacología , Glicina Hidroximetiltransferasa/antagonistas & inhibidores , Plasmodium falciparum/efectos de los fármacos , Plasmodium vivax/efectos de los fármacos , Administración Oral , Animales , Antimaláricos/administración & dosificación , Antimaláricos/farmacocinética , Técnicas de Química Sintética , Cristalografía por Rayos X , Evaluación Preclínica de Medicamentos/métodos , Resistencia a Medicamentos/efectos de los fármacos , Inhibidores Enzimáticos/síntesis química , Femenino , Glicina Hidroximetiltransferasa/química , Glicina Hidroximetiltransferasa/metabolismo , Células Hep G2/efectos de los fármacos , Humanos , Hígado/metabolismo , Hígado/parasitología , Malaria Falciparum/tratamiento farmacológico , Malaria Falciparum/parasitología , Ratones Endogámicos , Ratones SCID , Microsomas Hepáticos/efectos de los fármacos , Organismos Modificados Genéticamente , Plasmodium berghei/efectos de los fármacos , Plasmodium berghei/patogenicidad , Plasmodium falciparum/enzimología , Plasmodium falciparum/patogenicidad , Plasmodium vivax/enzimología , Plasmodium vivax/patogenicidad , Pirazoles/química , RatasRESUMEN
Enzymes of the non-mevalonate pathway for isoprenoid biosynthesis are therapeutic targets for the treatment of important infectious diseases. Whereas this pathway is absent in humans, it is used by plants, many eubacteria and apicomplexan protozoa, including major human pathogens such as Plasmodium falciparum and Mycobacterium tuberculosis. Herein, we report on the design, preparation and biological evaluation of a new series of ligands for IspE protein, a kinase from this pathway. These inhibitors were developed for the inhibition of IspE from Escherichia coli, using structure-based design approaches. Structure-activity relationships (SARs) and a co-crystal structure of Aquifex aeolicus IspE bound to a representative inhibitor validate the proposed binding mode. The crystal structure shows that the ligand binds in the substrate-rather than the adenosine 5'-triphosphate (ATP)-binding pocket. As predicted, a cyclopropyl substituent occupies a small cavity not used by the substrate. The optimal volume occupancy of this cavity is explored in detail. In the co-crystal structure, a diphosphate anion binds to the Gly-rich loop, which normally accepts the triphosphate moiety of ATP. This structure provides useful insights for future structure-based developments of inhibitors for the parasite enzymes.