Patients are often treated with multiple simultaneous medications, which generates a risk for significant drug-drug interactions that may affect the efficacy of one or several drugs and even lead to hospitalizations. Hence, it is required that DDI risks are evaluated while developing new therapies. To manage the risk of the drug development program facing significant DDI risk related challenges, it is recommendable to screen for the DDI potential early on, during hit-to-lead stage. Our team at Admescope has long-standing expertise in screening discovery stage compounds for their DDI profiles covering a range of enzyme inhibitions and inductions.
CYP inhibition is typically investigated with liver microsomes utilizing a cost-effective cocktail approach, where all the seven major CYPs are investigated in a single incubation to address reversible and time dependent inhibition. The assay can be tailored to deliver full IC50/IC50 shift evaluation for regulatory purposes or used for a more streamlined approach with fewer test concentrations for screening. CYP inhibition can also be evaluated using pooled hepatocytes, for more comprehensive analysis with non-CYP hepatic enzymes that may be present.
CYP induction can be screened reliably and cost-efficiently using pooled hepatocytes. Induction of the three major CYPs, CYP1A2, CYP2B6 and CYP3A4, are most reliably evaluated with mRNA endpoint. In addition, it is recommended to couple the assay with cytotoxicity evaluation, which helps interpretation of the results. An alternative approach for induction screening is to evaluate human PXR nuclear receptor activation, a transcription factor leading to CYP3A4 and CYP2C induction.
Besides CYP enzymes, for some compounds it’s necessary to look at other enzymes, too. Clinical examples exist for UGT DDIs and thus, it is recommended to also investigate UGT inhibition, utilizing recombinant enzymes. UGT induction can also be investigated in hepatocytes with the mRNA endpoint. There are numerous other non-CYPs enzymes, a comprehensive list can be found on our website.
For regulatory compliant DDI evaluation, the testing concentrations for the test article are chosen to represent clinically relevant or predicted concentrations. Testing concentrations may also be limited based on in vitro solubility or cytotoxicity. For evaluating these factors, several pre-tests can be included, such as free fraction in the in vitro incubation conditions or plasma, kinetic solubility, or cytotoxicity before proceeding to the actual study.
In addition to the enzyme inhibition and induction assays, our service portfolio covers assays for evaluating transporter mediated DDI, among the comprehensive panel of in vitro metabolism assays.
Would you like to learn more about the topic of drug-drug interactions in general? You’ll find much more material on the Admescope website, containing free e-books for download.
