The Drug-Drug Interaction between Erlotinib and OSI-930 Is Mediated through Aldehyde Oxidase Inhibition

The propensity for aldehyde oxidase (AO) substrates to be implicated in drug-drug interactions (DDI) is not well-understood due to the dearth of potent inhibitors that elicit in vivo inhibition of AO. While there is only one reported instance of DDI that has been ascribed to the inhibition of AO to-date, the supporting evidence for this clinical interaction is rather tenuous and its veracity has been called into question. Our group recently reported that the epidermal growth factor receptor inhibitor erlotinib engendered potent time-dependent inhibition of AO with inactivation kinetic constants in the same order of magnitude as its free circulating plasma concentrations. At the same time, it was previously reported that the concomitant administration of erlotinib with the investigational drug OSI-930 culminated in a similar to 2-fold increase in its systemic exposure. Although the basis underpinning this interaction remains unclear, the structure of OSI-930 contains a quinoline motif which is amenable to oxidation at the electrophilic carbon adjacent to the nitrogen atom by molybdenum-containing hydroxylases like AO. In this study, we conducted metabolite identification which revealed that OSI-930 undergoes AO metabolism to a mono-oxygenated 2-oxo metabolite and assessed its formation kinetics in human liver cytosol. Additionally, reaction phenotyping in human hepatocytes revealed that AO contributes nearly similar to 50% to the overall metabolism of OSI-930. Finally, modelling the interaction between erlotinib and OSI-930 using a mechanistic static model projected an similar to 1.85-fold increase in the systemic exposure of OSI-930 - which accurately recapitulated clinical observations. SIGNIFICANCE STATEMENT In this study, we delineate an AO metabolic pathway in the investigational drug OSI-930 for the first time and confirmed that it represented a major route of metabolism through reaction phenotyping in human hepatocytes. Our study provided compelling mechanistic and modelling evidence for the first instance of an AO-mediated clinical DDI stemming from the in vivo inhibition of the AO-mediated quinoline 2-oxidation pathway in OSI-930 by erlotinib.