Inhaleable spray dried 4-helix bundle protein powders having minimized aggregation

A method for preparing an inhaleable 4-α helix bundle protein powder having superior aerosolizability and protein stability upon spray drying, said method comprising:

• (a) dissolving a 4-alpha helix bundle protein in an aqueous solvent in the absence of surfactant to form a solution, and
• (b) spray drying said solution under conditions effective to produce a powder characterized by (i) an emitted dose of at least about 65%, and (ii) a total protein aggregate content of less than 10%

A spray-dried, inhaleable human growth hormone powder having superior aerosolizability and protein stability, comprising human growth hormone,

• wherein said powder is free from surfactant and characterized by (i) an emitted dose of at least about 65%, and (ii) a total protein aggregate content of less than 10%.