Absorption and Disposition of Coproporphyrin I (CPI) in Cynomolgus Monkeys and Mice: Pharmacokinetic Evidence to Support the Use of CPI to Inform the Potential for Organic Anion-Transporting Polypeptide Inhibition.

Despite a recent expansion in the recognition of the potential utility of coproporphyrin (CP) as an endogenous biomarker of organic anion-transporting polypeptide (OATP) 1B activity, there have been few detailed studies of CP's pharmacokinetic behavior and an overall poor understanding of its pharmacokinetic fate from tissues and excretion. Here, we describe the pharmacokinetics of octadeuterium-labeled coproporphyrin I (CPI-d8) in cynomolgus monkeys following oral and intravenous administration. CPI-d8 has a half-life and bioavailability of 7.6 hours and 3.2%, respectively. Cynomolgus monkeys received oral cyclosporin A (CsA) at 4, 20, and 100 mg/kg which yielded maximum blood concentrations ( ) and area under the plasma concentration-time curve (AUC) values of 0.19, 2.5, and 3.8 µM, and 2.7, 10.5, and 26.6 µM·h, respectively. The apparent CsA-dose dependent increase in the AUC ratio of CPI-d8 (1.8, 6.2, and 10.5), CPI (1.1, 1.4, and 4.4), and CPIII (1.1, 1.8, and 4.6) at 4, 20, and 100 mg, respectively. In contrast, the plasma concentrations of CPI and CPIII were generally not affected by intravenous administration of the renal organic anion and cation transporter inhibitors (probenecid and pyrimethamine, respectively). In addition, tritium-labeled coproporphyrin I ([H]CPI) showed specific and rapid distribution to the liver, intestine, and kidney after an intravenous dose in mice using quantitative whole-body autoradiography. Rifampin markedly reduced the liver and intestinal uptake of [H]CPI while increasing the kidney uptake. Taken together, these results suggest that hepatic OATP considerably affects the disposition of CPI in animal models, indicating CPI is a sensitive and selective endogenous biomarker of OATP inhibition. SIGNIFICANCE STATEMENT: This study demonstrated that coproporphyrin I (CPI) has favorable oral absorption, distribution, and elimination profiles in monkeys and mice as an endogenous biomarker. It also demonstrated its sensitivity and selectivity as a probe of organic anion-transporting polypeptide (OATP) 1B activity. The study reports, for the first time, in vivo pharmacokinetics, tissue distribution, sensitivity, and selectivity of CPI as an OATP1B endogenous biomarker in animals. The data provide preclinical support for exploration of its utility as a sensitive and selective circulating OATP biomarker in humans.