Physicochemical evaluation of lyophilized formulation of p-SCN-Bn-DOTA-and p-SCN-Bn-DTPA-rituximab for NHL radioimmunotherapy

Radioimmunotherapy (RIT) of Non-Hodgkin’s lymphoma (NHL) is said to be more advantageous compared to unlabelled therapeutic antibodies. To this date, radiolabelled murine anti-CD20 mAbs, Zevalin® and Bexxar® have been approved for imaging and therapy. A preparation containing rituximab, chimeric mAb radioimmunoconjugate suitable for Lu-177 labeling, could provide better imaging and therapeutic profile at the same time. This study was conducted to evaluate prepared lyophilized formulations of two rituximab immunoconjugates, intended for immediate Lu-177 labeling, for imaging and therapy.
The characterization of the conjugates and demonstration of the integrity of the protein and purity after conjugation and lyophilization was performed by SDS-PAGE, FT-IR and MALDI-TOF-MS. The results showed preserved antibody structure and average of 6.1 p-SCN-Bn-DOTA and 8.8 p-SCN-Bn-DTPA groups per antibody molecule which is suitable for successful labeling. These results support the possibility of developing a “ready-to-label” rituximab immunoconjugates for NHL imaging/therapy.