Development and Characterization of a Dry Powder Formulation for Anti-Tuberculosis Drug Spectinamide 1599.

PURPOSE: Human tuberculosis (TB) is a global health problem that causes nearly 2 million deaths per year. Anti-TB therapy exists, but it needs to be administered as a cocktail of antibiotics for six months. This lengthy therapy results in low patient compliance and is the main reason attributable to the emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains of Mycobacterium tuberculosis. METHODS: One alternative approach is to combine anti-TB multidrug therapy with inhalational TB therapy. The aim of this work was to develop and characterize dry powder formulations of spectinamide 1599 and ensure in vitro and in vivo delivered dose reproducibility using custom dosators. RESULTS: Amorphous dry powders of spectinamide 1599 were successfully spray dried with mass median aerodynamic diameter (MMAD) = 2.32 ± 0.05 µm. The addition of L-leucine resulted in minor changes to the MMAD (1.69 ± 0.35 µm) but significantly improved the inhalable portion of spectinamide 1599 while maintaining amorphous qualities. Additionally, we were able to demonstrate reproducibility of dry powder administration in vitro and in vivo in mice. CONCLUSIONS: The corresponding systemic drug exposure data indicates dose-dependent exposure in vivo in mice after dry powder intrapulmonary aerosol delivery in the dose range 15.4 - 32.8 mg/kg.

Inhaled Pyrazinoic Acid Esters for the Treatment of Tuberculosis.

PURPOSE: Analog development of existing drugs and direct drug delivery to the lungs by inhalation as treatments for multiple and extensively drug resistant (MDR and XDR) tuberculosis (TB) represent new therapeutic strategies. Pyrazinamide (PZA) is critical to drug sensitive TB therapy and is included in regimens for MDR TB. However, PZA-resistant Mycobacterium tuberculosis (Mtb) strains threaten its use. Pyrazinoic acid esters (PAEs) are PZA analogs effective against Mtb in vitro, including against the most common PZA resistant strains. However, PAEs require testing for TB efficacy in animal models. METHODS: PAEs were delivered daily as aqueous dispersions from a vibrating mesh nebulizer to Mtb infected guinea pigs for 4 weeks in a regimen including orally administered first-line TB drugs. RESULTS: PAEs tested as a supplement to oral therapy significantly reduced the organ bacterial burden in comparison to infected, untreated control animals. Thus, PAE aerosol therapy is a potentially significant addition to the regimen for PZA resistant MDR-TB and XDR-TB treatment. Interestingly, low dose oral PZA treatment combined with standard therapy also reduced bacterial burden. This observation may be important for PZA susceptible disease treatment. CONCLUSION: The present study justifies further evaluation of PZA analogs and their lung delivery to treat TB.

Disposable Dosators for Pulmonary Insufflation of Therapeutic Agents to Small Animals.

Development of new therapeutic products requires efficacy testing in an animal model. The pulmonary route of administration can be utilized to deliver drugs locally and systemically. Evaluation of dry powder aerosols necessitates an efficient dispersion mechanism to maintain high concentrations in an exposure chamber or for direct endotracheal administration. While solutions exist to expose animals by passive inhalation to dry powder aerosols, most require masses of powder in large excess of the dose delivered. This precludes conducting early feasibility studies as insufficient drug is available at the research or early development stage to support the dose delivery requirements for conventional aerosol delivery systems. When designing an aerosol drug product, aerodynamic performance can relate directly to delivery efficiency and efficacy. Dispersion of powder into an aerosol requires energy input sufficient to overcome interparticulate forces, and particle engineering approaches can substantially improve aerosol performance. We have developed a dispersion system (dosator) which can aerosolize engineered dry powder aerosols efficiently for the purpose of direct pulmonary insufflation, dispersion into an exposure system or generation for analytical purposes.

Filtration improves the performance of a high-throughput screen for anti-mycobacterial compounds.

The tendency for mycobacteria to aggregate poses a challenge for their use in microplate based assays. Good dispersions have been difficult to achieve in high-throughput screening (HTS) assays used in the search for novel antibacterial drugs to treat tuberculosis and other related diseases. Here we describe a method using filtration to overcome the problem of variability resulting from aggregation of mycobacteria. This method consistently yielded higher reproducibility and lower variability than conventional methods, such as settling under gravity and vortexing.