IN VITRO ASSESSMENT OF REVERSIBLE AND METABOLISM-DEPENDENT INHIBITORY EFFECTS OF PROPOXAZEPAM ON CYP2C8 ACTIVITY.

Abstract

Background: In oncology, drug-drug interactions (DDIs) are particularly relevant due to the complex medication regimens of cancer patients. These patients often require multiple drugs to manage both their disease and treatment-related side effects. Evaluating potential DDIs via the inhibition of CYP enzymes is crucial in drug discovery. This study aimed to assess the effect of propoxazepam on CYP2C8 activity in vitro by amodiaquine N-deethylation in human liver microsomes and to predict the likelihood of DDI through CYP activity reduction.

Materials and methods: Amodiaquine Ndeethylation was used as a marker of CYP2C8 activity. The positive controls included montelukast (1 μM) for rever sible inhibition and gemfibrozil O-glucuronide (40 μM) for metabolism-dependent inhibition. Propoxazepam was tested in both reversible and metabolism-dependent inhibition conditions being added with the substrate or pre-incubated with microsomes and NADPH, respectively. The metabolite formation was quantified by LC-MS/MS in a multiple reaction monitoring mode using the electrospray ionization technique.

Results: Propoxazepam inhibited CYP2C8 activity in a concentration-dependent manner, with IC50 values of 20.5 ± 2.2 μM for reversible inhibition and 23.1 ± 3.2 μM for metabolism-dependent inhibition. Positive controls montelukast and gemfibrozil O-glucuronide showed expected inhibition (4.4% and 12.2% of control, respectively). Propoxazepam showed low binding to microsomal protein under the experimental conditions.

Conclusion: Based on the indicators used (Ki, IC50, IC50 shift, and [I]/Ki ratios), propoxazepam is not expected to be a significant CYP2C8 inhibitor in vitro.