Faustine Ravon1,2, Elena Menchi1, Myriam Remmelink3, Selma Chraibi1, Véronique Fontaine2 & Nathalie Wauthoz1
1Unit of Pharmaceutics and Biopharmaceutics, Faculty of Pharmacy, Université Libre de Bruxelles, Boulevard du Triomphe, Brussels, 1050, Belgium
2Unit of Microbiology, Bioorganic and Macromolecular Chemistry, Faculty of Pharmacy, Université Libre de Bruxelles, Boulevard du Triomphe, Brussels, 1050, Belgium
3Department of Pathology, Hôpital Erasme, Université Libre de Bruxelles, Route de Lennik 808, Brussels, 1070, Belgium
Summary
A drug combination, vancomycin (VAN) plus tetrahydrolipstatin (THL), has demonstrated an effective synergistic action in vitro against Mycobacterium tuberculosis (Mtb), inhibiting the growth of the bacilli as well as its resistant forms. Given the poor oral bioavailability of VAN and THL, and the tropism of tuberculosis for lungs, this combination is more suitable for administration by inhalation. To evaluate the local tolerability of this combination, bronchial cells, alveolar cells, and monocytes were exposed to different concentrations around the combination’s minimal inhibitory concentration (MIC) of the drugs (i.e., 10 mg/mL for VAN and 1 mg/mL for THL). The VAN-treated group never reached the half MIC (IC50), even at a concentration 80 times higher than the combination MIC. However, for THL-treated and VAN/THL-treated groups, the IC50 measured 30 to 50 times the combination MIC, due to the action of THL. It was demonstrated, using a lactate dehydrogenase assay, that this effect was related to a cytostatic and not a cytotoxic action. Subsequently, an in vivo experiment was performed at a concentration of 50 times the combination MIC, administered 3 times a week for 3 weeks on different groups of healthy mice, using an endotracheal device. Pro-inflammatory biomarkers (i.e., IL-1β, IL-6, and TNF-α) in bronchoalveolar lavage fluid remained insignificant vs. the negative control group, and lung histopathology did not show significant tissue damage. The VAN/THL combination at doses up to 50 times the combination MIC seems very well tolerated in vitro and in vivo; a promising result which encourages us to continue the development of an inhalation form of this combination to fight Mtb.
Key Message
The present work shows local tolerance of a potential anti-tuberculosis drug combination in vitro and in vivo. To date, this represents the first tetrahydrolipstatin study with administration by inhalation that provides the absence of cytotoxic activity and leads to multiple possibilities of use.