Design, synthesis, and characterization of a dual modality positron emission tomography and fluorescence Imaging agent for monoclonal antibody tumor-targeted imaging

A novel lysine-based trifunctional chelate 3 was designed, synthesized, and characterized and bears both a chelating moiety (CHX-A '') for sequestering radiometals (Y-86 or In-111) and the near-infrared dye Cy5.5 for dual modality PET (or SPECT) and fluorescence imaging, respectively. Successful conjugation of 3 to the monoclonal antibody trastuzumab (Herceptin) was achieved by efficient thiol-maleimide chemistry, thereby yielding immunoconjugate 2. Analysis of 2 by flow cytometry and competitive binding assay demonstrates that immunoconjugate 2 binds to SKOV3 tumor cells comparably to native trastuzumab and, thus, may be used as a tumor-targeted monoclonal antibody probe for multimodality imaging.