DEVELOPMENT AND VALIDATION OF AN LC-MS/MS ASSAY FOR THE QUANTIFICATION OF FEDRATINIB IN HUMAN PLASMA AND DRIED BLOOD SPOT MATRICES

Objectives: The objective of the study was to develop and validate a highly sensitive and robust LC-MS/MS method for the quantification of fedratinib (FRB), a selective Janus kinase 2 inhibitor used in the treatment of myelofibrosis, in both human plasma and dried blood spot (DBS) samples as per ICH M10 guidelines. Methods: Quantification was performed using a liquid chromatography-tandem mass spectrometry system equipped with electrospray ionization and multiple reaction monitoring. DBS samples were prepared using Whatman 903 cards, with FRB extracted efficiently to enable low-volume, stable, and decentralized sampling. Calibration was established over the range of 36–3,600 ng/mL. Results: The method demonstrated excellent selectivity, precision, and accuracy, with recoveries of 63.1% (plasma) and 77.1% (DBS) for FRB, and 60.9% (plasma), and 87.4% (DBS) for the internal standard. Stability assessments confirmed robustness under bench-top, auto sampler, and long-term conditions. Comparative analysis of plasma and DBS matrices showed strong agreement: Passing-Bablok regression indicated a slope close to 1 with negligible intercept, and Bland-Altman analysis revealed a mean bias of approximately −2%, well within the bioanalytical acceptance limits (