Biopharmaceutical optimization of antibiotic therapy for the treatment of Mycobacterium abscessus pulmonary infections : interest of nebulization and antibiotic combinations

Mycobacterium abscessus is rapidly growing non-tuberculous mycobacteria responsible for difficult-to-treat pulmonary infections in humans. Current recommended treatment is associated with high treatment failure and emergence of resistance to most of the antibiotics. Also, with only a few new antibiotic drugs active against multidrug-resistant bacteria approved every year, it is important to optimize the use of already existing antibiotics using biopharmaceutical approach like Pharmacokinetic/pharmacodynamic (PK/PD). In pulmonary infections, direct administration of low permeability drugs such as cefoxitin (FOX) and amikacin (AMK) into lungs as therapeutic aerosols should increase their efficiency and minimize whole body exposure responsible for adverse effects, particularly in the case of prolonged treatments. Moreover, the use of antibiotics in combination may reduce the risk of resistance. Several points have been addressed in this thesis: 1.Biopharmaceutical studies of AMK and FOX: It was shown that after nebulization of AMK and FOX, pulmonary concentrations were almost 1000-fold higher than after intravenous administration for both antibiotics, making them a good candidate for nebulization. 2.Pharmacokinetic/pharmacodynamic (PK/PD) study of cefoxitin: a semi-mechanistic PK/PD model was developed from in vitro time kill-kinetics assay data, enabling identification of concentration-effect relationships for two bacterial sub-populations while taking into account the unstability degradation of cefoxitin.3.PK/PD study of bi-combination: Using a mechanism-based mathematical model and data obtained from time kill-kinetics study, it was shown that the combined effect of AMK and FOX was additive to synergistic at different concentration.4.Bi-or tri-combinations: several tri-combinations including AMK, FOX and a 3rd antibiotic (including clarithromycin, linezolid, clofazimine, ciprofloxacin, moxifloxacin, rifampicin and rifabutin) were tested against reference strain, clarithromycin resistance-clinical isolate (Ma1611) and multidrug-resistance-clinical isolate (T28). All tri-combinations were active against reference strain. Similar observation was made with Ma1611 except combination with clofazimine and clarithromycin. Any combination was active against T28. Bi-combinations with highest concentrations of FOX and rifamycins were effective against T28. The synergy between FOX and fluoroquinolones or rifamycins suggests a potent role of these combinations that may warrant further optimization of treatment regimen for the treatment of M. abscessus pulmonary infections. 5.Tri-combination including AMK, FOX and moxifloxacin (MXF) up to 21 days against clarithromycin-resistance clinical isolate has shown no importance of using MXF as tri-combination was not more effective than the bi-combination of AMK and FOX.