A novel approach to monitoring Cyp3a induction and inhibition by bioluminescent urinalysis.

Background: Adverse drug-drug interactions (DDI) may occur when one drug accelerates or slows a second drug's metabolism by, respectively, inducing or inhibiting a cytochrome P450 (CYP) that metabolizes that second drug. We developed an method employing urinalysis to complement CYP induction and inhibition measurements widely used to predict DDIs.

Research Design And Methods: Focusing on Cyp3a enzymes, the major mammalian drug metabolizers, we applied luciferin-IPA, a selective Cyp3a probe substrate to mice after Cyp3a inducers and inhibitor treatments. Cyp3a converts the probe to a metabolite that is eliminated in urine and drives light output when mixed with a luciferase reaction mixture. We hypothesized that urine from an initial renal elimination phase would, respectively, drive elevated or reduced light output as a reflection of Cyp3a induction or inhibition.

Results: Luciferase mixed with urine from Cyp3a-induced mice showed enhanced signals, while a Cyp3a inhibitor diminished induced and basal signals versus vehicle.

Conclusions: A Cyp3a-selective luminogenic probe substrate enables rapid urinalysis-based testing for detecting Cyp3a induction and inhibition and predicting Cyp3a-dependent DDIs. The study serves as a proof of concept for using caged luciferins for enzyme activity tests with a readily accessible sample type.