Bioanalysis of tucatinib and metabolite, and a five-way cross-validation to support clinical pharmacokinetic analysis.

Tucatinib, a tyrosine kinase inhibitor of HER2, is approved in multiple regions for metastatic breast cancer and is being evaluated in metastatic colorectal and gastric cancers. During clinical development, quantification of tucatinib plasma concentrations for pharmacokinetic analysis was performed using MS/MS analysis by three laboratories using five different methods. Cross-validation was required to confirm data across laboratories were comparable. A five-way cross-validation procedure was developed where bioanalysis performed by one laboratory and method was used as a 'base' against which the other methods were validated. This cross-validation method provides an alternative to multiple head-to-head comparisons between two methods, and enabled combination of data from multiple tucatinib clinical trials for a single population pharmacokinetic analysis.