DOTA chelation through click chemistry enables favorable biodistribution of89Zr-radiolabeled antibodies: A comparison with DFO chelation

Currently, the DFO chelator is commonly used to conjugate monoclonal antibodies (mAbs) and 89 Zr, whereas the DOTA chelator is commonly used to conjugate mAbs and alpha- and beta-emitting metal radionuclides. However, if the degradation of [ 89 Zr]Zr-DFO-mAb is not negligible, the in vivo biodistribution of 89 Zr might not reflect that of metal radionuclides conjugated with DOTA-mAb. We hypothesized that [ 89 Zr]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 [ 89 Zr]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 89 Zr. Methods We prepared [ 89 Zr]Zr-DOTA-trastuzumab from DOTA-tetrazine conjugates (DOTA-Tz) and transcyclooctene-trastuzumab conjugates (TCO-trastuzumab). We first radiolabeled DOTA-Tz with 89 Zr in a reaction solution of MeOH and HEPES buffer and then used a click reaction to obtain [ 89 Zr]Zr-DOTA-Tz/TCO-trastuzumab. We performed biodistribution studies and PET imaging with [ 89 Zr]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 [ 89 Zr]Zr-DFO-trastuzumab. Results TCO-trastuzumab was radiolabeled with [ 89 Zr]Zr-DOTA-Tz in the two-step reaction in good radiochemical yield (57.8 ± 17.6%). HER2-positive tumors were clearly visualized with [ 89 Zr]Zr-DOTA-trastuzumab in PET imaging studies. The temporal profile changes of 89 Zr radioactivity in SKOV3 tumors and bone marrow were sufficiently different between [ 89 Zr]Zr-DOTA-trastuzumab and [ 89 Zr]Zr-DFO-trastuzumab (P < 0.05). Conclusion: [ 89 Zr]Zr-DOTA-trastuzumab can be produced by the two-step radiolabeling reaction based on the Tz/TCO click reaction. Presumably, 89 Zr released from DFO is not negligible. In contrast, [ 89 Zr]Zr-DOTA-mAb would better predict the biodistribution of [ 177 Lu]Lu- or [ 225 Ac]Ac-DOTA-mAb than [ 89 Zr]Zr-DFO-mAb, thus avoiding the use of different chelator for 89 Zr at the expense of the click chemistry step. Graphical Abstract