Targeting Pantothenate Kinase as an Effective Strategy for Antifungal Drug Development.

Fungal infections affect over one billion people worldwide each year and are the leading cause of mortality by eukaryotic pathogens with an estimated 150 million severe life-threatening cases and 1.7 million deaths reported annually. The rapid increase in the number of clinical cases and the emergence of multidrug resistant pathogens such as Candida auris emphasize the urgent need for new strategies to develop more effective, selective and safe antifungals. Coenzyme A (CoA) plays a central role in key cellular processes including the citric acid cycle, lipid metabolism, and ergosterol biosynthesis. The first step in the CoA biosynthesis pathway is catalyzed by a pantothenate kinase (PanK), which phosphorylates pantothenic acid (PA, or vitamin B5) to form phosphopantothenate. In fungi, this enzyme is encoded by a single copy PanK gene, which plays an essential role in cell viability. Here, we report the first crystal structure of the S. cerevisiae PanK enzyme, Cab1, at 1.8Å resolution. Cab1 was crystallized alone and in the presence of three lead high-affinity inhibitors identified in a high-throughput chemical screen of a library of 156,593 small molecules. Structure-guided mutagenesis together with functional complementation assays in yeast identified key residues in Cab1 that are essential for catalysis, substrate binding and dimerization. Structure activity relationship and biological assays identified a lead inhibitor YU385599, with excellent activity against the human pathogens Candida albicans, C. glabrata, and C. parapsilosis. Together, our data validate PanK activity as a novel drug target and identify a novel class of small molecules for the treatment of fungal diseases.