Development of a Theranostic Agent for Bone Metastases: Integration of Nuclear Medicine Imaging and Boron Neutron Capture Therapy (BNCT).

Boron neutron capture therapy (BNCT) is one of the promising cancer treatment methods with 10B-labeled compounds and neutron irradiation. The 10B(n,α)7Li reaction produces a 7Li nucleus and an α-particle with high linear energy transfer, which are responsible for the therapeutic effects. We hypothesized that BNCT could effectively treat bone metastases by selectively accumulating 10B at metastatic lesion sites. In this study, we designed, synthesized, and evaluated [nat/67Ga]Ga-DOTA-K(ε-closo-dodecaborate)D11 ([nat/67Ga]6), a compound integrating closo-dodecaborate for BNCT, a [nat/67Ga]Ga-DOTA derivative for nuclear imaging, and D11, an aspartic acid peptide, for bone targeting. [67Ga]6 and its precursor 5, which lacks gallium coordination, showed comparable biodistribution in normal mice, with high bone uptake and minimal off-target accumulation. These results support the potential of [nat/67/68Ga]6 as an effective theranostic agent for bone metastases.