Validation and clinical application of an LC-MS/MS method designed to simultaneously measure seven second-line TB drugs and two metabolites in human lung tissue.

We developed and validated a novel bioanalytical method for the simultaneous quantification of levofloxacin, linezolid, moxifloxacin, delamanid, bedaquiline, clofazimine, and pretomanid, along with the metabolites of delamanid (DM-6705) and bedaquiline (N-desmethyl-bedaquiline, M2), in human lung tissue samples. Following homogenization by bead beating and extraction by protein precipitation, the analytes were separated on an Agilent 1260 Infinity II HPLC system using a Poroshell 120 C18 EC (2.1 mm×50 mm, 2.7 µm) column with gradient elution, applying a mobile phase consisting of 0.1 % formic acid in water and 0.1 % formic acid in a mixture of acetonitrile and methanol. Detection and quantification of the analytes and their stable isotope labelled internal standards were performed on a Sciex API 5500 QTrap mass spectrometer using positive electrospray ionization and multiple reaction monitoring. Validation according to the guidelines of the FDA and EMA proved the method to be precise, accurate, and robust with no significant influence of matrix components. The application of the method to the analysis of clinical samples demonstrated the feasibility of quantifying the second-line anti-tuberculosis drugs in human lung tissue and the potential to provide insights into the drug distribution across the infection sites in the lung.