Development and validation of a sensitive LC-MS/MS assay for determination of upadacitinib in human plasma and its application in patients with inflammatory bowel disease.

Background: Upadacitinib is a selective Janus kinase (JAK) 1 inhibitor approved by the Food and Drug Administration for the treatment of moderate-to-severe inflammatory bowel disease (IBD). We aimed to establish and validate a method for determining Upadacitinib in patients with IBD by liquid chromatography-tandem mass spectrometry (LC-MS/MS) method.

Methods: The mobile phase was 0.