Clinical Investigation of Coproporphyrins as Sensitive Biomarkers to Predict Mild to Strong OATP1B-Mediated Drug-Drug Interactions.

INTRODUCTION: Coproporphyrin (CP) I and III have recently been proposed as endogenous clinical biomarkers to predict organic anion-transporting polypeptide 1B (OATP1B)-mediated drug-drug interactions (DDIs). In the present study, we first investigated the in vitro selectivity of CPI and CPIII towards drug uptake and efflux transporters. We then assessed the in vivo biomarker sensitivity towards OATP1B inhibition.
METHODS: To assess transporter selectivity, incubations with CPI and CPIII were performed in vitro, using single transporter-expressing and control systems. Furthermore, CPI and CPIII plasma concentrations were determined from participants of three independent clinical trials who were administered with either a strong, moderate, or mild clinical OATP1B inhibitor.
RESULTS: Our results show that CPI and CPIII are substrates of OATP1B1, OATP1B3, the multidrug resistance-associated protein (MRP) 2, and MRP3. No substrate interaction was shown for other prominent drug transporters that have been associated with clinical DDIs. Results from clinical studies demonstrated that changes in CPI and CPIII plasma levels were predictive for moderate (two to threefold area under the concentration-time curve [AUC] increase) and strong (≥ fivefold increases) clinical OATP1B inhibition. Furthermore, CPI, but not CPIII, concentration changes were predictive for a mild clinically observed DDI where CPI AUC increases of 1.4-fold were comparable with those observed for pitavastatin as victim drug (AUC increases of 1.5-fold).
CONCLUSION: Our results demonstrate the selectivity of CPI and CPIII towards the OATP1B/MRP pathway, and the herein reported data further underline the potential of CPI and CPIII as selective and sensitive clinical biomarkers to quantify OATP1B-mediated DDIs.