Investigation of an OATP1B inhibitory effect by a cyclic peptide using the endogenous biomarker coproporphyrin-I in...

Peptide drugs are expected to be a new modality that will replace traditional small molecule drugs. As the number of approved peptide drugs increases, they are being co-administered with various drugs, but there is a limited number of reports on their drug-drug interaction (DDI) in both in vitro and in vivo (clinical) studies. In this study, we investigated the transporter inhibitory potential of Compound A, a macrocyclic peptide (3.5 kDa) for the treatment of pain. We found that Compound A exhibited a strong inhibitory effect on the organic anion transporting polypeptide (OATP) 1B in an in vitro study. To assess the in vivo OATP1B inhibitory potential, Compound A was intravenously or subcutaneously administered to monkeys, and the plasma concentration of coproporphyrin-I (CP-I), an endogenous biomarker of OATP1B, was determined. Compound A markedly increased the CP-I concentration in monkeys. A semi-mechanistic pharmacokinetic model analysis using the CP-I concentration revealed that Compound A is a highly potent in vivo OATP1B inhibitor (in vivo K_{i, OATP1B}: 59.9 ng/mL as total plasma concentration). Our findings suggest that even peptides with a large molecular weight can cause DDI. These results offer valuable information for the further development of DDI guidelines for peptides.