Preclinical Aspects of [⁸⁹Zr]Zr-DFO-Rituximab: A High Potential Agent for Immuno-PET Imaging

An early diagnosis of cancer can lead to choosing more effective treatment and increase the number of cancer survivors. In this study, the preparation and preclinical aspects of [⁸⁹Zr]Zr-DFO-Rituximab, a high-potential agent for PET imaging of Non- Hodgkin Lymphoma (NHL), were evaluated.

DFO was conjugated to rituximab monoclonal antibody (mAb), and DFO-rituximab was successfully labeled with zirconium-89 (⁸⁹Zr) at optimized conditions. The stability of the complex was assessed in human blood serum and PBS buffer. Radioimmunoreactivity (RIA) of the radioimmunoconjugate (RIC) was evaluated on CD20-overexpressing Raji cell line and CHO cells. The biodistribution of the radiolabeled mAb was studied in normal and tumorbearing rodents. Finally, the absorbed dose in human organs was estimated.

The radiolabeled compound was prepared with radiochemical purity (RCP) >99% (RTLC) and a specific activity of 180±1.8 GBq/g. The RCP of the final complex PBS buffer and human blood serum was higher than 95%, even after 48 h post incubation. The RIA assay demonstrated that more than 63% of the radiolabeled compound (40 ng/ml, 0.5 mL) was bound to 5×10⁶ Raji cells. The biodistribution of the final product in tumor-bearing mice showed a high accumulation of the RIC in the tumor site in all intervals post-injection. Tumor/non-target ratios were increased over time, and longer imaging time was suggested. The dosimetry data indicated that the liver received the most absorbed dose after the complex injection.

[⁸⁹Zr]Zr-DFO-Rituximab represents a significant advancement in the field of oncological imaging and offers a robust platform for both diagnostic and therapeutic applications in the management of B-cell malignancies.