OBJECTIVE To investigate the change of the human interferon α2b(hIFN α2b) solution in inhalability and bioactivity following storage under accelerated and long-term stability testing conditions. And to evaluate the suitability for pulmonary delivery of hIFN α2b through nebulization, specifically for treating lower respiratory tract infections caused by respiratory syncytial virus in children within the product’s shelf life.

METHODS The real-time droplet size and distribution of the nebulized hIFN α2b were evaluated using a laser diffraction, while the aerodynamic particle size distribution(APSD) was analyzed with the next generation pharmaceutical impactor(NGI). The respirable drug delivery rate and total delivered dose were determined under a breathing simulator(BRS). Additionally, the bioactivity of hIFN α2b in aerosol was measured with a cytopathic-effect inhibition assay.

RESULTS The droplet size distribution analysis revealed a Dx(50) of 3.57 μm when utilizing a jet nebulizer. Aerodynamically, the aerosol exhibited a fine particle fraction(FPF) of 76.9% and a mass median aerodynamic diameter(MMAD) of 3.31 μm, with a geometric standard deviation(GSD) of 1.94. The delivery rate and total delivered dose under a child breathing pattern were 0.68×10⁵ IU·min⁻¹ and 5.31×10⁵ IU, respectively. Results showed that no significant change was observed in the droplet size distribution, aerodynamic parameters, delivery efficiency and the bioactivity of aerosol after storage under accelerated stability testing conditions for 6 months and long-term stability testing conditions for 24 months. All relative standard deviation(RSD) values were <6%.

CONCLUSION The droplet size of hIFN α2b aerosol is suitable for delivering to the lower respiratory tract after nebulization with a jet nebulizer. Furthermore, no significant change is found in the inhalability or bioactivity of the nebulized hIFN α2b under accelerated stability testing conditions for 6 months and long-term stability testing conditions for 24 months.