Development of a Bioanalytical Assay for the Selective RET Inhibitor Pralsetinib in Plasma Samples Utilizing Liquid Chromatography-Tandem Mass Spectrometry

Pralsetinib is a potent and specific tyrosine kinase inhibitor targeting the RET receptor, used in treating various cancers. This study developed and validated a bioanalytical assay for pralsetinib in plasma using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The internal standard was erlotinib, and protein precipitation with acetonitrile was used for sample preparation. The analytes were separated on an Ultimate® XB-C18 column using gradient elution with ammonium acetate in water and methanol. Both are acidified with 0.1% formic acid. Detection was performed using positive electrospray ionization in the chosen reaction monitoring mode. The assay was validated over a linear range of 2 to 2000 ng/mL, achieving accuracies greater than 90% and precision values below 2%. The method was stable under all tested conditions without significant matrix effects or extraction losses.