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

Background: 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.

Methods: 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.

Results: 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.

Conclusion: [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.