Three spectroscopic techniques evaluated as a tool to study the effects of iodination of monoclonal antibodies, exemplified by rituximab.

Radioiodinated monoclonal antibodies have been used for radioimmunotherapeutic and radiodiagnostic purposes. Radioiodination of monoclonal antibodies may lead to deterioration of the immunoreactivity of the monoclonal antibody. Methods for the determination of the immunoreactivity, however, do not provide information about any structural changes of the radioconjugate which may influence the binding properties of the protein to the target antigen. Within this study we demonstrated the potential role of three alternative spectroscopic analytical techniques to characterize the structural changes emerging after iodination of rituximab. We conclude that techniques as liquid chromatography coupled to mass spectrometry, fluorescence emission spectrophotometry, and circular dichroism can provide valuable information about structural changes of a radiolabeled compound, e.g. during pharmaceutical development and for quality control.