Tumor Marker–Guided Precision BNCT for CA19-9–Positive Cancers: A New Paradigm in Molecularly Targeted Chemoradiation Therapy

Background Boron neutron capture therapy (BNCT) is a molecularly targeted chemoradiation modality that relies on boron delivery agents such as p-borophenylalanine (BPA), which require LAT1 (L-type amino acid transporter 1) for tumor uptake. However, the limited efficacy of BPA in LAT1-low tumors restricts its therapeutic scope. To address this limitation, we developed a tumor marker–guided BNCT strategy targeting cancers overexpressing the clinically validated glycan biomarker CA19-9. Methods We conducted transcriptomic analyses using The Cancer Genome Atlas (TCGA) datasets to identify LAT1-low cancers with high CA19-9 expression. These analyses revealed elevated expression of fucosyltransferase 3 (FUT3), which underlies CA19-9 biosynthesis, in pancreatic, biliary, and ovarian malignancies. Based on this, we synthesized a novel boron compound, fucose-BSH, designed to selectively accumulate in CA19-9–positive tumors. We evaluated its physicochemical properties, pharmacokinetics, biodistribution, and antitumor efficacy in cell lines and xenograft models, comparing its performance to that of BPA. Results Fucose-BSH demonstrated significantly greater boron uptake in CA19-9–positive cell lines (AsPC-1, Panc 04.03, HuCCT-1, HSKTC, OVISE) compared to CA19-9–negative PANC-1. In HuCCT-1 xenografts, boron accumulation reached 36.2 ppm with a tumor/normal tissue ratio of 2.1, outperforming BPA. Upon neutron irradiation, fucose-BSH–mediated BNCT achieved > 80% tumor growth inhibition. Notably, fucose-BSH retained therapeutic efficacy in LAT1-deficient models where BPA was ineffective, confirming LAT1-independent targeting. Conclusions This study establishes a novel precision BNCT approach by leveraging CA19-9 as a tumor-selective glycan marker for boron delivery. Fucose-BSH offers a promising platform for expanding BNCT to previously inaccessible LAT1-low malignancies, including pancreatic, biliary, and ovarian cancers. These findings provide a clinically actionable strategy for tumor marker–driven chemoradiation and lay the foundation for translational application in BNCT.