Bioanalysis of INCB000928 in human saliva: nonspecific binding and inhomogeneous concentration.

To develop a bioanalytical method for quantifying INCB000928 in human saliva. Human centrifuged saliva and human whole saliva were compared for matrix selection. Protein precipitation extraction and HPLC-MS/MS was used for analysis. Nonspecific binding of INCB000928 was reduced in whole versus centrifuged saliva. Whole saliva was a preferred matrix for INCB000928 bioanalytical method validation. Incurred sample reanalysis (ISR) using a successfully validated method failed in a healthy volunteer study because of inhomogeneous INCB000928 concentration across sample tube depths. Individual mixing of sample tubes followed by immediate aliquoting corrected the ISR failure, with 97.2% of repeats passing versus 41.7% for the same ISR samples.