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. This strategy has the potential to support companion diagnostic development and precision stratification in ongoing and future BNCT clinical trials.
Translational Relevance: Malignancies with elevated CA19-9 expression, such as pancreatic, biliary, and ovarian cancers, are associated with poor prognosis and limited response to current therapies. This study presents a tumor marker–guided strategy for boron neutron capture therapy (BNCT) by leveraging CA19-9 glycan biology to enable selective tumor targeting via fucose-BSH, a novel boron compound. Through transcriptomic data mining and preclinical validation, fucose-BSH demonstrated LAT1-independent boron delivery, potent BNCT-mediated cytotoxicity, and tumor-specific accumulation in CA19-9–positive models. These findings support a precision chemoradiation approach that addresses a critical gap in BNCT applicability, offering a clinically actionable pathway for patient stratification and therapeutic development in CA19-9–expressing cancers.