Enzyme Kinetics, Pharmacokinetics, and Inhibition of Aldehyde Oxidase

Area of Science:

• Biochemistry
• Pharmacology
• Drug Metabolism

Background:

• Aldehyde oxidase (AO) is an increasingly recognized drug-metabolizing enzyme.
• Preclinical species often underestimate human AO activity, leading to clinical trial failures.
• Significant differences exist in AO activity across species, with dogs lacking functional AO.

Purpose of the Study:

• To review the multifaceted roles of aldehyde oxidase in drug metabolism.
• To highlight the implications of AO-catalyzed oxidation and reduction on drug clearance and toxicity.
• To discuss the challenges and opportunities in studying AO, including drug-drug interactions (DDIs) and computational predictions.

Main Methods:

• Literature review of aldehyde oxidase (AO) metabolism.
• Analysis of AO-catalyzed oxidation and reduction pathways.
• Examination of species-specific differences in AO activity.
• Discussion of implications for drug development and DDI assessment.

Main Results:

• AO catalyzes both oxidative and reductive metabolic transformations.
• Oxidative metabolism yields generally non-reactive products with low solubility.
• Reductive metabolism can produce reactive metabolites, leading to toxicity, and involves substrates like nitro-compounds and N-oxides.
• AO can reduce oxygen to reactive oxygen species (ROS) and nitrite to nitric oxide.

Conclusions:

• Aldehyde oxidase plays a complex role in drug metabolism, influencing both clearance and toxicity.
• Species differences in AO activity necessitate careful consideration in preclinical drug development.
• Complex inhibition kinetics require multiple probe substrates for accurate DDI assessment.
• Computational prediction of AO regioselectivity and reaction rates shows promise for virtual screening.