Respirable Clofazimine Particles Produced by Air Jet Milling Technique Are Efficacious in Treatment of BALB/c Mice with Chronic Mycobacterium Tuberculosis Infection

Tuberculosis (TB) remains a major cause of morbidity and mortality, particularly in low- and middle-income countries where access to health care workers, cold-chain storage, and sterile water sources may be limited. Inhaled drug delivery is a promising alternative to systemic delivery of antimycobacterial drugs, as it enables rapid achievement of high infection-site drug concentrations. The off-patent drug clofazimine (CFZ) may be particularly suitable for this route, given its known systemic toxicities. In this study, micronized CFZ particles produced by air jet milling were assessed for shelf-stability, pharmacokinetics, and anti-TB efficacy by the oral and pulmonary routes in BALB/c mice. Intratracheal instillation of micronized CFZ particles produced several-fold higher lung concentrations after a single 30 mg/kg dose compared to delivery via oral gavage, and faster onset of bactericidal activity was observed in lungs of mice with chronic Mycobacterium tuberculosis infection compared to the oral route. Both infection status and administration route affected the multidose pharmacokinetics (PK) of micronized CFZ. Increased lung and spleen accumulation of the drug after pulmonary administration was noted in infected mice compared to naive mice, while the opposite trend was noted in the oral dosing groups. The infection-dependent PK of inhaled micronized CFZ may point to a role of macrophage trafficking in drug distribution, given the intracellular-targeting nature of the formulation. Lastly, air jet milled CFZ exhibited robustness to storage-induced chemical degradation and changes in aerosol performance, thereby indicating the suitability of the formulation for treatment of TB in regions with limited cold chain supply.