Toward the Optimization of Click-Mediated Pretargeted Radioimmunotherapy

Pretargeted radioimmunotherapy (PRIT) based on the inverse electron demand Diels–Alder reaction has shown promise in murine models of disease, yet the radiation dosimetry of this approach must be optimized to make it a viable clinical option. To this end, we have leveraged two recent developments in pretargeted imaging—dendritic scaffolds and masking agents—to improve the dosimetric profile of a proof-of-concept PRIT system that is based on the huA33 antibody, a 177Lu-labeled tetrazine radioligand ([177Lu]Lu-DOTA-PEG7-Tz), and a mouse model of A33 antigen-expressing colorectal carcinoma. Pretargeting using an huA33 immunoconjugate bearing a trans-cyclooctene-decorated dendritic scaffold (sshuA33-DEN-TCO) produced significantly higher tumoral activity concentrations at 120 h post-injection (23.0 ± 2.2 %ID/g) than those achieved with an analogous, dendrimer-lacking immunoconjugate (12.7 ± 2.6 %ID/g). However, pretargeting using sshuA33-DEN-TCO also resulted in increased activity concentrations in the blood ...