Despite reports indicating the potential impact of post-translational modifications on the activity of a monoclonal anti-body, their prediction or monitoring post-administration remains a challenge. In addition, with the expiration of patents concerning the early generation of mAbs, the production of biosimilars is constantly increasing. Structural differences of biosimilars compared to the innovator product are commonly evaluated for the formulated product in the context of bio-similarity assessment. However, estimating their structural outcome after administration is particularly difficult. Due to the complexity of in vivo studies, there is a need to develop analytical strategies to predict PTMs consequently to their admin-istration and their impact on mAbs potency. Here, we identified and evaluated the modification kinetics of 4 asparagine deamidations and 2 aspartate isomerizations of infliximab innovator product (Remicade®) and two biosimilars (Inflectra® and Remsima®) in vitro using serum incubation at 37°C. The methodology was based on a bottom-up approach with capil-lary electrophoresis hyphenated with mass spectrometry analysis for an unequivocal assignment of modified and unmodi-fied forms. 2 asparagines demonstrated a gradual deamidation correlated with incubation time. The specific extraction efficiency was evaluated to determine possible changes in the antigen binding affinity of infliximab with the incubation. Results showed the possibility to achieve an additional aspect concerning biosimilarity assessment, oriented on the study of the structural stability after administration.