Sterilization of Mycobacterium tuberculosis infected samples using methanol preserves anti-tuberculosis drugs for subsequent pharmacological testing studies

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.

Preclinical Evaluation of Inhalational Spectinamide-1599 Therapy against Tuberculosis

The lengthy treatment time for tuberculosis (TB) is a primary cause for the emergence of multidrug resistant tuberculosis (MDR-TB). One approach to improve TB therapy is to develop an inhalational TB therapy that when administered in combination with oral TB drugs eases and shortens treatment. Spectinamides are new semisynthetic analogues of spectinomycin with excellent activity against Mycobacterium tuberculosis (Mtb), including MDR and XDR Mtb strains. Spectinamide-1599 was chosen as a promising candidate for development of inhalational therapy. Using the murine TB model and intrapulmonary aerosol delivery of spectinamide-1599, we characterized the pharmacokinetics and efficacy of this therapy in BALB/c and C3HeB/FeJ mice infected with the Mtb Erdman strain. As expected, spectinamide-1599 exhibited dose-dependent exposure in plasma, lungs, and ELF, but exposure ratios between lung and plasma were 12-40 times higher for intrapulmonary compared to intravenous or subcutaneous administration. In chronically infected BALB/c mice, low doses (10 mg/kg) of spectinamide-1599 when administered thrice weekly for two months provide efficacy similar to that of higher doses (50-100 mg/kg) after one month of therapy. In the C3HeB/FeJ TB model, intrapulmonary aerosol delivery of spectinamide-1599 (50 mg/kg) or oral pyrazinamide (150 mg/kg) had limited or no efficacy in monotherapy, but when both drugs were given in combination, a synergistic effect with superior bacterial reduction of >1.8 log₁₀ CFU was observed. Throughout the up to eight-week treatment period, intrapulmonary therapy was well-tolerated without any overt toxicity. Overall, these results strongly support the further development of intrapulmonary spectinamide-1599 as a combination partner for anti-TB therapy.