Antiangiogenic Human Monoclonal Antibody Ramucirumab Radiolabelling: In Vitro Evaluation on VEGFR2-positive Cell Lines
Abstract
Background/Aim: Radiolabelling of monoclonal antibodies (mAbs) could be beneficial in cancer diagnosis and therapy, however it may cause structural changes and consequently deteriorate their immunoreactivity. Materials and Methods: The therapeutic mAb ramucirumab (RAM) was technetium-99m labelled using either a direct or an indirect method with the use of two bifunctional chelating agents (HYNIC, DTPA).
The radiochemical purity was assessed using instant thin-layer chromatography (ITLC) and high-performance liquid chromatography (HPLC) technique. The affinity of radiolabelled RAM was tested on human cancer cell lines.
Results: The radiolabelling provided the following stable compounds: [Tc-99m]RAM, [Tc-99m]HYNIC-RAM and [Tc-99m]DTPA-RAM. Their radiochemical purity was over 95%.
All prepared radiopharmaceuticals showed moderate affinity to the targeted receptor, in vitro. However, their affinity was one order lower compared to that of the natural mAb.
Moreover, directly and DTPA-radiolabelled RAM demonstrated less favourable binding kinetics. Conclusion: Radiolabelling negatively affected the affinity of RAM to its targeted receptor.