Radiolabeling of IGF2R-specific mAb

The IGF2R-specific mAb 2G11 and the isotype matching control mAb MOPC-21 were labeled with the radioisotopes ¹¹¹In (¹¹¹In-2G11, ¹¹¹In-MOPC-21), ¹⁷⁷Lu (¹⁷⁷Lu-2G11, ¹⁷⁷Lu-MOPC-21) or ²¹³Bi (²¹³Bi-2G11). The radiolabeling of an antibody-CHXA” conjugate with ¹¹¹In was performed to achieve the specific activity of approximately 5 µCi/µg of the antibody. For example, 600 µCi of ¹¹¹In chloride was added to 10 µL 0.15 M ammonium acetate buffer and added to a microcentrifuge tube containing 120 µg 2G11-CHXA” conjugate in 0.15 M ammonium acetate buffer. The reaction mixture was incubated for 60 min at 37 °C, and then the reaction was quenched by the addition of 3 µL 0.05 M EDTA solution. The percentage of radiolabeling was measured by SG-iTLC using 0.15 M ammonium acetate buffer as the eluent. SG-iTLCs were cut in half and read on a Perkin Elmer 2470 Automatic Gamma Counter (top containing unlabeled ¹¹¹In, bottom containing antibody conjugated ¹¹¹In). ¹⁷⁷Lu labeling was performed with an identical protocol using ¹⁷⁷Lu as the radioisotope, and labeling with ²¹³Bi was carried out as in^{26 (link)}. ¹¹¹In, ¹⁷⁷Lu and ²¹³Bi incorporation was >95%.