Evaluation of Icotinib as a Potent and Selective Inhibitor of Aldehyde Oxidase for Reaction Phenotyping in Human Hepatocytes

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

“…On the contrary, the EGFR inhibitor erlotinib was reported to elicit potent direct inhibition of AO at clinically-relevant in vivo concentrations (Tan et al, 2020). Our group extended that previous work by showing that in addition to the direct inhibition of AO, erlotinib could also engender potent time-dependent inhibition with inactivation kinetic constants in the same order of magnitude as its unbound steady-state plasma concentrations (Hidalgo et al, 2001;Liu et al, 2024;Tang et al, 2024). All things equal, time-dependent inhibition is usually more pertinent from a DDI perspective due to the irreparable loss of enzymatic activity.…”

“…Estimation of f m,AO . Estimation of the f m,AO in human hepatocytes using the AO inactivator icotinib has been previously described by our laboratory (Tang et al, 2024). Briefly, the CL int,app of OSI-930 from substrate depletion experiments in human hepatocytes was derived using Equations 3 -5…”

“…In the above equations, K i is the reversible (direct) inhibition constant; k inact and K I is the maximal inactivation rate and time-dependent inhibition constant, respectively. As it was determined that erlotinib competitively inhibits AO (Tan et al, 2020), K i values were estimated from our previously derived erlotinib IC 50 values against human liver cytosolic AOconducted at ~KM substrate concentrationby dividing by two (i.e., K i = IC 50 /2) (Cheng and Prusoff, 1973;Tang et al, 2024). The inactivation kinetic parameters for erlotinib against human liver cytosolic AO have also been experimentally determined in our previous study (Tang et al, 2024).…”

“…As it was determined that erlotinib competitively inhibits AO (Tan et al, 2020), K i values were estimated from our previously derived erlotinib IC 50 values against human liver cytosolic AOconducted at ~KM substrate concentrationby dividing by two (i.e., K i = IC 50 /2) (Cheng and Prusoff, 1973;Tang et al, 2024). The inactivation kinetic parameters for erlotinib against human liver cytosolic AO have also been experimentally determined in our previous study (Tang et al, 2024). Both the K i and K I were transformed to their corresponding unbound values (i.e., K i,u and K I,u ) by correcting for the cytosolic free fraction (f u,cytosol ) of erlotinib.…”

“…Taken together, this suggests that AO can be a target of metabolic DDI and that clinical inhibitors of AO which are more potent than cimetidine are likely to generate a more profound interaction with a victim drug that has a moderate to high fraction metabolized by AO (f m,AO ). At this juncture, our group recently characterized the potent direct and time-dependent inhibition of human AO by the epidermal growth factor receptor (EGFR) inhibitor erlotinib (Liu et al, 2024;Tang et al, 2024). Notably, our previous study also suggested that the inhibition of AO by erlotinib could be clinically relevant as the AO inhibition kinetic constants derived were in the same order of magnitude as its unbound steady-state plasma concentrations (Hidalgo et al, 2001;Fiala et al, 2017).…”