Radiolabelling rituximab with (99m)Tc in three steps procedure.

Area of Science:

• Hematologic Oncology
• Radiopharmaceutical Chemistry
• Molecular Imaging

Background:

• Non-Hodgkin's lymphomas (NHL) are common hematologic malignancies, with over 90% of tumor cells expressing CD 20.
• Current remission evaluation using PET/CT with [(18)F]FDG lacks specificity, failing to differentiate residual tumor from inflammation.
• There is a critical need for specific imaging agents to detect residual CD 20-positive lymphoma.

Purpose of the Study:

• To develop and validate a specific radiotracer for targeting CD 20-positive NHL cells.
• To create a method for radiolabeling rituximab, an anti-CD 20 antibody, for clinical use.
• To assess the efficacy of the developed radiotracer in detecting residual lymphoma.

Main Methods:

• Developed a novel radiolabeling technique using a (99m)Tc-tricarbonyl compound with Isolink®.
• Rituximab was radiolabeled in a three-step procedure without antibody reduction, preserving protein integrity.
• Evaluated radiolabeling yield (>97%), in vitro antibody integrity, and in vivo tumor targeting using SPECT/CT.

Main Results:

• The radiolabeling process achieved high yields (>97%) and maintained rituximab integrity.
• In vivo SPECT/CT demonstrated significant tumor targeting of the radiotracer 24 hours post-injection.
• The developed immunoradiolabeling method successfully detected residual disease in preclinical models.

Conclusions:

• A novel, specific radiotracer for CD 20-positive NHL has been successfully developed.
• The method is fast, reproducible, gentle, and compliant with Good Manufacturing Practices.
• This immunoradiotracer offers a promising tool for specific detection of residual lymphoma post-therapy.