Mechanically-induced aggregation of the monoclonal antibody cetuximab.

This study focuses on the mechanically-induced aggregation of the anticancer monoclonal antibody cetuximab and its mechanism by comparing two commercially-available formulations (old formulation [OF]: 2mg/ml in phosphate buffer; new formulation [NF]: 5mg/ml in citrate buffer with polysorbate 80 and glycine). Cetuximab aggregation under stirring was followed during a 24h period and several methods were used to describe the aggregation kinetics (turbidimetry, size-exclusion high performance liquid chromatography, cation-exchange chromatography, dynamic light scattering and peptide mapping). Depending on the formulation, the aggregation process followed different kinetics: biexponential for the OF and mono-exponential for the NF. The percentage of aggregation after 24h stirring-period was about 25% for the OF but was only 2% for the NF corresponding to a ten-fold improvement, demonstrating a strong protecting effect of polysorbate and glycine. The aggregates are mainly due to an increased exposure of antibody molecules to air/liquid interface and are formed without chemical alteration of the antibody structure. This improvement of cetuximab stability by a new formulation seems linked to the stabilisation of cetuximab under dimeric form by a higher protein concentration and the presence of stabilizing excipients.