Aim: 4-pyridoxic acid (PDA) has been proposed as an endogenous biomarker for renal organic anion transporter 1/3 (OAT1/3) inhibition. Clinical data are needed to support the proposal. Materials & methods: A hydrophilic interaction chromatography (HILIC)–LC/MS/MS assay was developed and characterized to support clinical drug–drug interaction (DDI) studies. Results: A HILIC–LC/MS/MS assay was successfully developed. PDA was measured in two clinical DDI studies; one where no significant OAT1/3 inhibition was observed and a second where a known inhibitor of the transporter was dosed. In both clinical studies, PDA plasma concentrations correlate to OAT1/3 function. Conclusion: The analysis of study samples from two clinical DDI studies using a HILIC–LC/MS/MS assay contributes further evidence that PDA is an endogenous biomarker for OAT1/3 inhibition.
Keywords:
- 4-pyridoxic acid (PDA)
- biomarkers
- characterization
- HILIC
- OAT1/3