Powder aerosol formulation of Pseudomonas aeruginosa bacteriophage for pulmonary delivery

The purpose of this study was to develop Pseudomonas aeruginosa bacteriophage 95 (ATCC 14211-B1) as a stable and aerosolizable dry powder formulation. We specifically investigated the effects of different excipients (e.g. trehalose, lactose, leucine, mannitol, gelatin and hydrolyzed gelatin) on the aerosol performance and stabilization of spray dried bacteriophage powder formulations. Our data demonstrated that hydrolyzed gelatin was the most effective bacteriophage stabilizer during spray drying, showing a titer reduction of only 0.6 log. When stored at 4 °C, hydrolyzed gelatin and gelatin showed the best stability with negligible bacteriophage titer reduction for 12 weeks. The in vitro aerosol performance of spray dried formulations was assessed using a multistage liquid impinger coupled with a low-resistance RS01 inhaler device.The hydrolyzed gelatin formulation showed an emitted dose (ED) of 60 % and fine particle fraction (FPF) of 77 %. The inclusion of leucine and trileucine at 5 % w/w significantly improved the aerosol performance of the hydrolyzed gelatin-bacteriophage formulation to an ED of 90 % and an FPF of 80-86 %; both were amorphous matrix that showed low bacteriophage titer reduction (0.7 log). This is the first study to report that a composite spray dried matrix of hydrolyzed gelatin (as a stabilizer) with leucine or trileucine (as dispersion enhancers) provides both high bacteriophage stability and excellent aerosol performance, making it a promising dry powder formulation for treating pulmonary bacterial infections.