Structure-Based Design, Synthesis, and Characterization of Inhibitors of Human and Plasmodium falciparum Dihydroorotate Dehydrogenases

Pyrimidine biosynthesis is an attractive drug target in a variety of organisms, including humans and the malaria parasite Plasmodium falciparum. Dihydroorotate dehydrogenase, an enzyme catalyzing the only redox reaction of the pyrimidine biosynthesis pathway, is a well-characterized target for chemotherapeutical intervention. In this study, we have applied SPROUT-LeadOpt, a software package for structure-based drug discovery and lead optimization, to improve the binding of the active metabolite of the anti-inflammatory drug leflunomide to the target cavities of the P. falciparum and human dihydroorotate dehydrogenases. Following synthesis of a library of compounds based upon the SPROUT-optimized molecular scaffolds, a series of inhibitors generally showing good inhibitory activity was obtained, in keeping with the SPROUT-LeadOpt predictions. Furthermore, cocrystal structures of five of these SPROUT-designed inhibitors bound in the ubiquinone binding cavity of the human dihydroorotate dehydrogenase are also analyzed.