A highly selective and sensitive LC–MS/HRMS assay for quantifying coproporphyrins as organic anion-transporting peptide biomarkers

Aim: Coproporphyrin-I (CP-I) and coproporphyrin-III (CP-III) in plasma and urine have been proposed as biomarkers for assessing drug–drug interactions involving hepatic drug transporters such as organic anion-transporting peptides (OATP), 1B1 and 1B3. Materials & methods: Plasma and urine extracts were analyzed for CP-I/CP-III using a TripleTOF API6600 mass spectrometer. Results: Previously unreported, CP-I/CP-III doubly charged ions (m/z 328.14) were used as precursor ions to improve the assay sensitivity and selectivity over the singly charged precursor ions (m/z 655.28). Levels of CP-I and CP-III measured ranged 0.45–1.1 and 0.050–0.50 ng/ml in plasma and 5–35 and 1–35 ng/ml in urine, respectively. Conclusion: The described highly selective and...