A proof-of-concept study on bioorthogonal-based pretargeting and signal amplify radiotheranostic strategy.

ABSTRACT

BACKGROUND: Radiotheranostics differs from the vast majority of other cancer therapies in its capacity for simultaneous imaging and therapy, and it is becoming more widely implemented. A balance between diagnostic and treatment requirements is essential for achieving effective radiotheranostics. Herein, we propose a proof-of-concept strategy aiming to address the profound differences in the specific requirements of the diagnosis and treatment of radiotheranostics. RESULTS: To validate the concept, we designed an s-tetrazine (Tz) conjugated prostate-specific membrane antigen (PSMA) ligand (DOTA-PSMA-Tz) for 68Ga or 177Lu radiolabeling and tumor radiotheranostics, a trans-cyclooctene (TCO) modified Pd@Au nanoplates (Pd@Au-PEG-TCO) for signal amplification, respectively. We then demonstrated this radiotheranostic strategy in the tumor-bearing mice with the following three-step procedures (1) i.v. injection of the [68Ga]Ga-PSMA-Tz for diagnosis; (2) i.v. injection of the signal amplification module Pd@Au-PEG-TCO; (3) i.v. injection of the [177Lu]Lu-PSMA-Tz for therapy. Firstly, this strategy was demonstrated in 22Rv1 tumor-bearing mice via positron emission tomography (PET) imaging with [68Ga]Ga-PSMA-Tz. We observed significantly higher tumor uptake (11.5 ± 0.8%ID/g) with the injection of Pd@Au-PEG-TCO than with the injection [68Ga]Ga-PSMA-Tz alone (5.5 ± 0.9%ID/g). Furthermore, we validated this strategy through biodistribution studies of [177Lu]Lu-PSMA-Tz, with the injection of the signal amplification module, approximately five-fold higher tumor uptake of [177Lu]Lu-PSMA-Tz (24.33 ± 2.53% ID/g) was obtained when compared to [177Lu]Lu-PSMA-Tz alone (5.19 ± 0.26%ID/g) at 48 h post-injection. CONCLUSION: In summary, the proposed strategy has the potential to expand the toolbox of pretargeted radiotherapy in the field of theranostics.