Characterization and aerodynamic evaluation of spray dried recombinant human growth hormone using protein stabilizing agents.

The effect of the protein stabilizers on the stability and aerosol performance of spray dried recombinant human growth hormone (SD rhGH) was investigated. rhGH solution was spray dried alone, with polysorbate 20 (at three concentrations of 0.05%, 0.01%, and 0.005%), Zn(2+) (by Zn(2+):rhGH molar ratio of 2:1 and 4:1), and/or lactose (by lactose:rhGH weight ratio of 2:1). Size exclusion chromatography (SEC) analysis of spray dried powders demonstrated that of all the potential protein stabilizers, the combination of polysorbate 20 (0.05%), Zn(2+) (Zn(2+):rhGH molar ratio of 2:1) and lactose (lactose:rhGH weight ratio of 2:1) was the most effective at protecting rhGH against aggregation during spray drying. The results of circular dichroism (CD) analysis revealed that using of polysorbate 20 (in all concentrations) and Zn(2+) (by Zn(2+):rhGH molar ratio of 2:1) together in the formulations would preserve rhGH conformational stability during the process. The particle size distribution data obtained by laser diffraction method showed all SD rhGH formulations had volume median diameter and mean diameter below 5mum. The characterization of the aerosol performance of the spray dried powders by Andersen cascade impactor (ACI) showed that by increasing the concentration of polysorbate 20 in the formulations the aerodynamic efficiency of the resultant particles was reduced. In conclusion, the optimum amounts of polysorbate 20, Zn(2+) and lactose satisfied both physical stability during spray drying process (2.37% aggregation) and good aerosol performance (fine particle fraction; FPF=38.52%).