Effect of Microencapsulation Shear Stress on the Structural Integrity and Biological Activity of a Model Monoclonal Antibody, Trastuzumab

The aim of the present study was to investigate the influence of process shear stressors on the stability of a model monoclonal antibody, trastuzumab. Trastuzumab, at concentrations of 0.4–4.0 mg/mL, was subjected to sonication, freeze-thaw, lyophilisation, spray drying and was encapsulated into micro- and nanoparticles. The stressed samples were analysed for structural integrity by gel electrophoresis, SDS-PAGE, and size exclusion chromatography (SEC), while the conformational integrity was analysed by circular dichroism (CD). Biological activity of the stressed trastuzumab was investigated by measuring the inhibition of cell proliferation of HER-2 expressing cell lines. Results show that trastuzumab was resistant to the process shear stresses applied and to microencapsulation processes. At the lowest concentration of 0.4 mg/mL, a low percent (<9%) of soluble/reversible aggregates may have been formed. No loss of structural integrity, conformation was observed and no significant change in the biological activity of trastuzumab was observed (ANOVA; p > 0.05). The results of this study conclude that trastuzumab may be resistant to various processing stresses. These findings have important implications with respect to pharmaceutical processing of monoclonal antibodies.