Development and validation of an LC–MS/MS method to quantify kynurenic acid in human plasma: supplementary data

Background: Monitoring levels of endogenous biomarkers has become an alternative approach to
assess transporter-mediated drug–drug interactions in clinical trials. Among the biomarkers of interest,
kynurenic acid is effective for the human organic anion transporters OAT1 and OAT3. Here, a simple
and robust bioanalytical method was developed using LC–MS/MS to quantify kynurenic acid in human
plasma. Results: This method achieved a LLOQ of 10 nm with acceptable signal-to-noise ratio (S/N >5).
In addition, an interfering agent, tryptophan, was identified and separated chromatographically. A full
method validation was performed in the spirit of GLP. Conclusion: This method can serve as a tool readily
available to assess potential drug–drug interactions mediated by inhibition of OAT1 and OAT3 activities.