Radiopharmaceuticals are radioactive medicines used for imaging and/or therapeutic purposes, consisting of radionuclidic and pharmaceutical parts. While PET and SPECT methods are used for imaging purposes, immuno-PET imaging method has gained popularity, recently. Immuno-PET imaging method, is a combination of PET radionuclides and biomolecules, especially monoclonal antibodies (mAb), proteins, peptides, are frequently used for the imaging of different types of cancer. Radionuclides with long half-lives are generally used in immuno-PET imaging. Long biological half-lives of mAbs is the most important reason to be preferred for immuno-PET imaging. Today, Zirconium-89 (Zr-89), Iodine-124 (I-124) with long half-lives and Copper-64 (Cu-64) and Yttrium-86 (Y-86) radionuclides with relatively long half-lives are preferred in immuno-PET imaging. In this article, studies on Zr-89, Cu-64, I-124 and Y-86-labeled mAbs with long half-life and clinical and preclinical studies were reviewed. Also, comparison of these 4 radionuclides, which are frequently used in the labelling of biomolecules (particularly mAbs) with is included.

Obinutuzumab (Obi) is a clinically approved a next-generation monoclonal antibody (mAb), showing specific binding to the CD20 B-cell surface markers which is a key target for B-cell malignancies. In this study, 89Zr-labelling Obi was optimised and the binding of the labelled agent was validated in an in-vitro model. Obi was radiolabelled with 89Zr with several different ratios to optimise the (mAb: DFO-Bz-NCS:89Zr) ratio with a small amount of it. The reason to employ the antibody as low quantity as possible in radiolabelling studies was the very high cost of antibodies. The radiolabelling studies were followed by in-vitro studies that would demonstrate the affinity of the formulations to the cells of CD20(+). Proving the specificity of 89Zr-Obi may be beneficial in diagnosing and monitoring CD20(+) tumours. Obi’s long half-life and high sensitivity to CD20 are important in this area.Graphical Abstract