Full Library

New antifungal drugs that act via novel mechanisms are urgently needed to combat the high mortality of invasive fungal disease and the emergence of resistance to existing therapies. We describe the discovery, structure, activity, and mechanism of action of F901318, a new antifungal agent. A member of a novel class of antifungals, the orotomides, F901318 acts via inhibition of dihydroorotate dehydrogenase, an enzyme of de novo pyrimidine biosynthesis. F901318 is currently in clinical development for the treatment of invasive aspergillosis., There is an important medical need for new antifungal agents with novel mechanisms of action to treat the increasing number of patients with life-threatening systemic fungal disease and to overcome the growing problem of resistance to current therapies. F901318, the leading representative of a novel class of drug, the orotomides, is an antifungal drug in clinical development that demonstrates excellent potency against a broad range of dimorphic and filamentous fungi. In vitro susceptibility testing of F901318 against more than 100 strains from the four main pathogenic Aspergillus spp. revealed minimal inhibitory concentrations of ≤0.06 µg/mL—greater potency than the leading antifungal classes. An investigation into the mechanism of action of F901318 found that it acts via inhibition of the pyrimidine biosynthesis enzyme dihydroorotate dehydrogenase (DHODH) in a fungal-specific manner. Homology modeling of Aspergillus fumigatus DHODH has identified a predicted binding mode of the inhibitor and important interacting amino acid residues. In a murine pulmonary model of aspergillosis, F901318 displays in vivo efficacy against a strain of A. fumigatus sensitive to the azole class of antifungals and a strain displaying an azole-resistant phenotype. F901318 is currently in late Phase 1 clinical trials, offering hope that the antifungal armamentarium can be expanded to include a class of agent with a mechanism of action distinct from currently marketed antifungals.

PMID: 27791100 PMCID: PMC5111691