Discovery, identification and mitigation of isobaric sulfate metabolite interference to a phosphate prodrug in LC–MS/MS bioanalysis: Critical role of method development in ensuring assay quality

2020 White Paper on Recent Issues in Bioanalysis: BAV Guidance, CLSI H62, Biotherapeutics Stability, Parallelism Testing, CyTOF and Regulatory Feedback ( Part 2A –Recommendations on Biotherapeutics Stability, PK LBA Regulated Bioanalysis, Biomarkers Assays, Cytometry Validation & Innovation Part 2B –Regulatory Agencies’ Inputs on Bioanalysis, Biomarkers, Immunogenicity, Gene & Cell Therapy and Vaccine)

“…OTR's bioanalytical program team performed a literature review to evaluate the potential risk of metabolite interference in LCMS and used four case studies to show how metabolite(s) can affect the quantitation of parent drug. The first case study is the quantitation of raltegravir in plasma using two methods which were all fully validated according to the EMA guidance but generated different results [95]; the second case study is the identification and mitigation of an isobaric sulfate metabolite to a phosphate prodrug [96]; the third case study illustrates two examples of isobaric metabolites with almost identical MS/MS profiles as parent drugs [97,98]; the last case study is about potentially new isobaric metabolite of fluvastatin observed by LCMS during incurred sample analysis in a BE study [99]. The last case study was very important since it is generally believed that metabolite(s) interfering was more likely to happen at discovery stage.…”