Optimization and characterization of spray-dried IgG formulations: a design of experiment approach

Background: The purpose of the present study is to optimize a spray-dried formulation as a model antibody regarding stability and aerodynamic property for further aerosol therapy of this group of macromolecules. Method: A three-factor, three-level, Box-Behnken design was employed milligrams of Cysteine (X-1), Trehalose (X-2), and Tween 20 (X-3) as independent variables. The dependent variables were quantified and the optimized formulation was prepared accordingly. SEC-HPLC and FTIR-spectroscopy were conducted to evaluate the molecular and structural status of spray-dried preparations. Particle characterization of optimized sample was performed with the aid of DSC, SEM, and TSI examinations. Results: Experimental responses of a total of 17 formulations resulted in yield values, (Y-1), ranging from 21.1 +/- 0.2 to 40.2 +/- 0.1 (%); beta-sheet content, (Y-2), from 66.22 +/- 0.19 to 73.78 +/- 0.26 (%); amount of aggregation following process, (Y-3), ranging from 0.11 +/- 0.03 to 0.95 +/- 0.03 (%); and amount of aggregation upon storage, (Y-4), from 0.81 +/- 0.01 to 3. 13 +/- 0.64 (%) as dependent variables. Results-except for those of the beta sheet content-were fitted to quadratic models describing the inherent relationship between main factors. Conclusion: Co-application of Cysteine and Tween 20 preserved antibody molecules from molecular degradation and improved immediate and accelerated stability of spry-dried antibodies. Validation of the optimization study indicated high degree of prognostic ability of response surface methodology in preparation of stable spray-dried IgG.