Labeling of Anti-SAS1B with Zirconium-89 as a Novel Immune-PET Probe for Uterine Cancer Imaging

Overexpression of Sperm Acrosomal SLLP1 Binding protein (SAS1B) in various cancer types, including uterine cancer cells, was discovered a few years ago, and different monoclonal antibodies (anti-SAS1B) that specifically bind to SAS1B antigens were developed. Labeling of these antibodies with radionuclides can provide an opportunity for imaging and radioimmunotherapy. The objective of this study was to label anti-SAS1B (SB5) with Zirconium-89 (89Zr) for PET imaging and determine its biodistribution. Anti-SAS1B (SB5) antibody was labeled with 89Zr indirectly using the chelator desferrioxamine B (DFO), which is currently a best linker for 89Zr. The antibody, SB5, was first conjugated to DFO with a ratio of 1:5 and then labeled with 250 μCi of 89Zr. Results of PET imaging in mouse-bearing uterine cancer tumor showed a limited uptake. The bio-distribution study matched the PET imaging and confirmed the uptake by the tumor, and the accumulation in bones. In conclusion, labeling of anti-SAS1B could provide an effective way of uterine cancer detection and treatment progression.