LC–MS/MS method for the quantitation of OCT1 biomarker isobutyrylcarnitine in human plasma with clinical sample analysis: supplementary data

Aim: Isobutyrylcarnitine (IBC) is a possible biomarker for hepatic OCT1, as IBC plasma concentrations are

reduced when OCT1 is inhibited. An accessible, characterized assay is needed to quantitate IBC in human

plasma. Materials & methods: A triple quadrupole MS surrogate matrix assay for the quantitation of

IBC was characterized to support a first-in-human study. Results: An assay for IBC quantitation was fully

characterized for accuracy, precision, selectivity and parallelism. IBC was measured in a clinical study and

the data were correlated to the in vitro model prediction. Conclusion: A triple quadrupole-based assay

for IBC should broaden the monitoring of IBC for OCT1 inhibition in early clinical trials, generating the

data needed to establish IBC as a valid biomarker.