Simultaneous Quantification of Vedolizumab, Ustekinumab, and Infliximab in Human Serum by LC-MS/MS: Application to Therapeutic Drug Monitoring in Inflammatory Bowel Disease

Purpose

With the expanding use of therapeutic monoclonal antibodies (mAbs) in inflammatory bowel disease (IBD), there is a critical need for robust, multiplex analytical tools to support therapeutic drug monitoring (TDM) and pharmacokinetic studies. This study aimed to develop and validate a rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous quantification of infliximab (IFX), vedolizumab (VDZ), and ustekinumab (UST) in human serum. Patients and methods: A universal immunocapture strategy utilizing Protein G magnetic beads was used to enrich total IgG from human serum. Samples were subjected to tryptic digestion and analyzed in multiple reaction monitoring (MRM) mode, with rituximab as a full-process internal standard. Method validation was performed in accordance with regulatory guidelines, evaluating linearity, precision, accuracy, selectivity, recovery, matrix effect, and stability. The validated method was subsequently applied to residual serum samples from IBD patients undergoing treatment.