DOTA chelation through click chemistry enables favorable biodistribution of 89Zr-radiolabeled antibodies: A comparison with DFO chelation

Currently, the DFO chelator is commonly used to conjugate monoclonal antibodies (mAbs) and 89Zr, whereas the DOTA chelator is commonly used to conjugate mAbs and alpha- and beta-emitting metal radionuclides. However, if the degradation of [89Zr]Zr-DFO-mAb is not negligible, the in vivo biodistribution of 89Zr might not reflect that of metal radionuclides conjugated with DOTA-mAb. We hypothesized that [89Zr]Zr-DOTA-mAb as a new imaging counterpart would accurately predict the biodistribution of therapeutic metal radionuclides delivered by DOTA-mAb. In this study, we prepared [89Zr]Zr-DOTA-trastuzumab for the first time by a two-step reaction using click chemistry and then investigated the differences in biodistribution profiles between two chelating approaches for 89Zr. Methods We prepared [89Zr]Zr-DOTA-trastuzumab from DOTA-tetrazine conjugates (DOTA-Tz) and transcyclooctene-trastuzumab conjugates (TCO-trastuzumab). We first radiolabeled DOTA-Tz with 89Zr in a reaction solution of MeOH and HEPES buffer and then used a click reaction to obtain [89Zr]Zr-DOTA-Tz/TCO-trastuzumab. We performed biodistribution studies and PET imaging with [89Zr]Zr-DOTA-trastuzumab in a mouse model of HER2-positive ovarian cancer, SKOV3 xenograft mice at 24, 72, and 144 hours post-injection and compared these data with those of [89Zr]Zr-DFO-trastuzumab. Results TCO-trastuzumab was radiolabeled with [89Zr]Zr-DOTA-Tz in the two-step reaction in good radiochemical yield (57.8 ± 17.6%). HER2-positive tumors were clearly visualized with [89Zr]Zr-DOTA-trastuzumab in PET imaging studies. The temporal profile changes of 89Zr radioactivity in SKOV3 tumors and bone marrow were sufficiently different between [89Zr]Zr-DOTA-trastuzumab and [89Zr]Zr-DFO-trastuzumab (P < 0.05). Conclusion: [89Zr]Zr-DOTA-trastuzumab can be produced by the two-step radiolabeling reaction based on the Tz/TCO click reaction. Presumably, 89Zr released from DFO is not negligible. In contrast, [89Zr]Zr-DOTA-mAb would better predict the biodistribution of [177Lu]Lu- or [225Ac]Ac-DOTA-mAb than [89Zr]Zr-DFO-mAb, thus avoiding the use of different chelator for 89Zr at the expense of the click chemistry step. ![Figure][1] ### Competing Interest Statement Ryota Imura and Hiroyuki Ida are employees of JFE Engineering Corporation. This research was partially conducted with research funds of the JFE Engineering Corporation. * DOTA : 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid DFO : deferoxamine B [1]: pending:yes