Cytochrome P450 (CYP) induction by a drug can accelerate the metabolism of a co-administered victim drug significantly, causing serious drug-drug interactions.
To date induction of CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, and CYP3A4 have been described. Whilst CYP1A2 induction involves the Aryl hydrocarbon receptor (AhR) and induction of CYP2B6 is mediated by the constitutive androstane receptor (CAR), the CYP2C isoforms and CYP3A4 are co-induced via the pregnane X receptor (PXR). Therefore, the current FDA guidelines suggest to investigate induction of CYP1A2, CYP2B6 and CYP3A4.
Traditionally, CYP induction has been measured via the assessment of enzyme activity in human hepatocytes. In order to address inter-individual variability, hepatocyte preparations from at least three donors had to be used.
HepaRG is an immortalised human hepatic cell line highly rated by scientist for its hepatocyte-like phenotype, e.g. its expression of drug-metabolising enzymes drug transporters and transcription factors.
Therefore, HepaRG provide an excellent, highly reproducible and cost-efficient system to study CYP induction during drug discovery or during the early phases of drug development.
Determination of mRNA levels by quantitative revers-transcription polymerase chain reaction (qRT-PCR) has proven superior over enzyme activity, because the latter could lead to false negative results when CYP induction was masked by simultaneous inhibition.
The XenoGesis CYP induction protocol
|CYPs isoforms||CYP1A2, CYP2B6, CYP3A4|
|Positive control inducers||Omeprazole, Phenobarbital, Rifampicin|
|Incubation time||24 hours|
|Test compound concentrations||0.32, 1.0,3.2, 10, 32 and 100 µM (others available)|
|Typical turnaround time||3 weeks|
Note: Assay conditions can be tailored to client requirements.
Chu V et al. (2009) In Vitro and in Vivo Induction of Cytochrome P450: A Survey of the Current Practices and Recommendations: A Pharmaceutical Research and Manufacturers of America Perspective. Drug Metabolism and Disposition 37(7): 1339-45