Use of Fc-Engineered Antibodies as Clearing Agents to Increase Contrast During PET.

UNLABELLED Despite promise for the use of antibodies as molecular imaging agents in PET, their long in vivo half-lives result in poor contrast and radiation damage to normal tissue. This study describes an approach to overcome these limitations. METHODS Mice bearing human epidermal growth factor receptor type 2 (HER2)-overexpressing tumors were injected with radiolabeled ((124)I, (125)I) HER2-specific antibody (pertuzumab). Pertuzumab injection was followed 8 h later by the delivery of an engineered, antibody-based inhibitor of the receptor, FcRn. Biodistribution analyses and PET were performed at 24 and 48 h after pertuzumab injection. RESULTS The delivery of the engineered, antibody-based FcRn inhibitor (or Abdeg, for antibody that enhances IgG degradation) results in improved tumor-to-blood ratios, reduced systemic exposure to radiolabel, and increased contrast during PET. CONCLUSION Abdegs have considerable potential as agents to stringently regulate antibody dynamics in vivo, resulting in increased contrast during molecular imaging with PET.