Process to Remove the Size Variants Contained in the Antibody–Chelator Complex PCTA-NCAB001 for Radiolabeling with Copper-64

Abstract

Understanding the physicochemical properties of antibody–drug conjugates is critical to assess their quality at manufacturing and monitor them during subsequent storage. For radiometal–antibody complexes, it is important to control the properties of the antibody–chelator conjugate to maintain the quality of the final product. We have been developing 64Cu-labeled anti-epidermal growth factor receptor antibody NCAB001 (64Cu-NCAB001) for the early diagnosis and therapy of pancreatic cancer with positron-emission tomography. Here, we characterized the larger size variants contained in the antibody–chelator conjugate PCTA-NCAB001 by multi-angle light scattering coupled with size-exclusion chromatography. Secondly, we developed a chromatographic method to remove these size variants. Lastly, we demonstrated the stability of PCTA-NCAB001 after the removal of size variants. Dimer and oligomers were identified in PCTA-NCAB001. These larger size variants, together with some smaller size variants, could be removed by hydrophobic interaction chromatography. The PCTA-NCAB001 product, after the removal of these size variants, could be stored at 4 °C for six months. The methods developed here can be applied to assure the quality of PCTA-NCAB001 and other antibody–drug conjugates to facilitate the development of antibody–radiometal conjugates for positron-emission tomography and radioimmunotherapy of malignant cancers.