Astatine-211 labeled anti-HER2 5F7 single domain antibody fragment conjugates: radiolabeling and preliminary evaluation

Derived from heavy chain only camelid antibodies, ~ 15-kDa single-domain antibody fragments (sdAbs) are an attractive platform for developing molecularly specific imaging probes and targeted radiotherapeutics. The rapid tumor accumulation and normal tissue clearance of sdAbs might be ideal for use with ²¹¹At, a 7.2-h half-life α-emitter, if appropriate labeling chemistry can be devised to trap ²¹¹At in cancer cells after sdAb binding. This study evaluated two reagents, [²¹¹At]SAGMB and iso-[²¹¹At]SAGMB, for this purpose.