A battery of tandem mass spectrometry assays with stable isotope-dilution for the quantification of 15 anti-tuberculosis drugs and two metabolites in patients with susceptible-, multidrug-resistant- and extensively drug-resistant tuberculosis

Objective Anti-tuberculosis (antiTB) drugs are characterized by an important inter-interindividual pharmacokinetic variability poorly predictable from individual patients' characteristics. Therapeutic drug monitoring (TDM) may therefore be beneficial for patients with Mycobacterium tuberculosis infection, especially for the management of multidrug/extensively drug resistant- (MDR/XDR)-TB. Our objective was to develop robust HPLC-MS/MS methods for plasma quantification of 15 antiTB drugs and 2 metabolites, namely rifampicin, isoniazid plus N-acetyl-isoniazid, pyrazinamide, ethambutol (the conventional quadritherapy for susceptible TB) as well as combination of agents against MDR/XDR-TB: bedaquiline, clofazimine, delamanid and its metabolite M1, levofloxacin, linezolid, moxifloxacin, pretomanid, rifabutin, rifapentine, sutezolid, and cycloserine. Methods Plasma protein precipitation was used for all analytes except cycloserine, which was analyzed separately after derivatization with benzoyl chloride. AntiTB quadritherapy drugs (Pool1) were separated by Hydrophilic Interaction Liquid Chromatography (column Xbridge BEH Amide, 2.1 × 150 mm, 2.5 μm, Waters®) while MDR/XDR-TB agents (Pool 2) and cycloserine (as benzoyl derivative) were analyzed by reverse phase chromatography on a column XSelect HSS T3, 2.1 × 75 mm, 3.5 µm (Waters®). All runs last Results The method covers the clinically relevant plasma levels and was extensively validated based on FDA recommendations, with intra- and inter-assay precision (CV) Conclusion Such convenient extraction methods and the use of stable isotope-labelled drugs as internal standards provide an accurate and precise quantification of plasma concentrations of all major clinically-used antiTB drugs regimens and is optimally suited for clinically efficient TDM against tuberculosis.