Olorofim, a potential novel drug candidate against Helicobacter pylori infection.

Helicobacter pylori infection is widely prevalent and can lead to peptic ulcer disease and gastric cancer. Treatment is challenged by a growing rate of antibiotic resistance. In this study, we evaluated the efficacy of olorofim (F901318), a DHODH inhibitor against Aspergillus fumigatus, in targeting H. pylori. The minimum inhibitory concentration (MIC) of olorofim against H. pylori reference and three multiple drug-resistant strains was determined. The nature of its growth inhibitory effect was assessed using liquid and solid bacterial culture. The general toxicity of olorofim was assessed against other bacteria and reassessed against eukaryotic cells. The effect of olorofim on DHODH activity was tested using a substrate reduction assay. Pairwise sequence alignment was carried out on H. pylori and A. fumigatus DHODH amino acid sequences. The MIC of olorofim against H. pylori reference strain and three MDR strains ranged from 0.075 to 0.625 µg mL. The growth-inhibitory effect was demonstrated to be bactericidal. Olorofim showed no general toxicity against other tested bacteria and was further confirmed to be non-toxic to eukaryotic cells. However, olorofim did not inhibit the activity of the recombinant H. pylori DHODH enzyme. Accordingly, sequence alignment revealed that four of the critical olorofim-binding residues in A. fumigatus DHODH differ in H. pylori. Olorofim demonstrated a strong bactericidal effect against H. pylori, making it a promising drug candidate for treating antibiotic-resistant cases. However, both our experimental findings and sequence analysis suggest that the DHODH enzyme in H. pylori is unlikely to be the molecular target of this drug candidate.