Preclinical evaluation of 89Zr/177Lu/161Tb-labeled anti-CD228 monoclonal antibody for theranostics in skin cutaneous melanoma.

This study aimed to develop 89Zr/177Lu/161Tb-labeled anti-CD228 monoclonal antibody (42C10HZ11) for immuno-positron emission tomography/computed tomography (immuno-PET/CT) and radioimmunotherapy (RIT) in skin cutaneous melanoma (SKCM). Anti-CD228 antibodies were conjugated with p-SCN-Bn-DFO or p-SCN-Bn-DOTA, followed by radiolabeling with 89Zr/177Lu/161Tb. The biological properties of the conjugates were assessed using radioligand cell binding, blocking, and internalization assays. Two cell line-derived xenograft preclinical models were established: CD228-high-expressing SK-MEL28 and CD228-low-expressing A375 models. Immuno-PET, biodistribution experiments, and RIT were performed. [89Zr]Zr-DFO-CD228, [177Lu]Lu-DOTA-CD228, and [161Tb]Tb-DOTA-CD228 showed high radiochemical purity (>95%) and good in vitro stability. For immuno-PET/CT, the mean standardized uptake value of SK-MEL28 model tumors at 96 h post-injection was 4.24 ± 0.32 (n = 3), significantly higher than that in SK-MEL28 blocking group and A375 group (P < 0.001). Ex vivo biodistribution studies demonstrated that tumor dose uptake increased over time and remained at a high level, while non-target organs showed rapid clearance. Both 11.1 MBq [177Lu]Lu-DOTA-CD228 and 11.1 MBq [161Tb]Tb-DOTA-CD228 significantly inhibited tumor growth, prolonged survival, and showed low toxicity. Notably, [161Tb]Tb-DOTA-CD228 demonstrated stronger anti-tumor efficacy than [177Lu]Lu-DOTA-CD228. We demonstrated that immuno-PET/CT with [89Zr]Zr-DFO-CD228 enables specific and precise non-invasive assessment of CD228 expression in SKCM models. [161Tb]Tb-DOTA-CD228 inhibited tumor growth more potently than [177Lu]Lu-DOTA-CD228 at the same administered activity, with preliminary mechanistic analyses suggesting that differential DNA damage, vascular responses, and immune modulation may account for the distinct anti-tumor effects of 161Tb and 177Lu, although further investigation is warranted. These findings provide preclinical evidence for CD228-targeted theranostics in SKCM.