Development of a Rapid and Simple LC-MS/MS Method for the Quantitation of Baricitinib in Human Plasma and Aqueous Humor

Abstract

BACKGROUND: Increasing evidence supports the off-label use of Janus kinase inhibitors for the treatment of noninfectious uveitis. Although several bioanalytical methods for determining baricitinib concentrations have been reported, no methods are currently available for monitoring concentrations at or near noninfectious uveitis lesions. This article aims to develop a rapid, sensitive, and reliable LC-MS/MS method for determining baricitinib concentrations in both plasma and aqueous humor, facilitating future clinical pharmacology research and improving therapeutic management. METHODS: After single-step protein precipitation and centrifugation, the samples were subjected to direct analysis. Optimal chromatographic performance was achieved using an Ultimate XB-C₁₈ column with a mobile phase of 10 mM of ammonium formate and a mixture of methanol, acetonitrile, and isopropanol (0.2% formic acid). RESULTS: The authors validated the method for the limits of detection and quantification, linearity, accuracy, precision, selectivity, matrix effects, stability, and recovery, with all results meeting guidelines. This method has been successfully applied to monitor baricitinib concentrations in adult patients with noninfectious uveitis, revealing substantial variability in plasma concentrations and unsynchronized pharmacokinetic changes between plasma and aqueous humor. CONCLUSION: This robust method can be a valuable tool for future clinical pharmacology research and improving therapeutic management.