Stabilizing formulations for inhalable powders of an adenovirus 35-vectored tuberculosis (TB) vaccine (AERAS-402)

A powder vaccine intended for aerosol delivery was formulated by spray drying the Ad35-vectored tuberculosis (TB) AERAS-402 vaccine with mannitol-based stabilizers. Thermodynamic properties, water absorption, particle size distribution and morphology of the powders were evaluated. Virus survival during spray drying and storage was determined by medium Tissue Culture Infectious Dose (TCID50). A mannitol-based powder (mannitol–cyclodextrin–trehalose–dextran, MCTD) had a narrow size distribution with a median volume diameter around 3.2–3.5 μm (suitable for pulmonary vaccination of humans) and good aerosolization characteristics. The spray dry powders generated from mannitol-based formulations were hydrophobic, which benefits virus survival during both production and storage at 4 °C, 25 °C and 37 °C as compared to the hygroscopic formulations (trehalose, sucrose, dextran, PVP, leucine). In conclusion, this study demonstrates that it is possible to produce in a one-step spray drying process a stable dry powder formulation of a TB vaccine suitable for mass vaccination.