Myoviridae bacteriophages were processed into a dry powder inhalable dosage form using a low-temperature spray-drying process. The phages were incorporated into microparticles consisting of trehalose, leucine, and optionally a third excipient (either a surfactant or casein sodium salt). The particles were designed to have high dispersibility and a respirable particle size, and to preserve the phages during processing. Bacteriophages KS4- M, KS14, and cocktails of phages ΦKZ/D3 and ΦKZ/D3/KS4-M were spray-dried with a processing loss ranging from 0.4 to 0.8 log pfu. The aerosol performance of the resulting dry powders as delivered from an Aerolizer® dry powder inhaler (DPI) exceeded the performance of commercially available DPIs; the emitted mass and the in vitro total lung mass of the lead formulation were 82.7% and 69.7% of filled capsule mass, respectively. The total lung mass had a mass median aerodynamic diameter of 2.5-2.8 µm. The total in vitro lung doses of the phages, delivered from a single actuation of the inhaler, ranged from 10(7) to 10(8) pfu, levels that are expected to be efficacious in vivo. Spray drying of bacteriophages into a respirable dry powder was found to be feasible.
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