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Boron neutron capture therapy(BNCT) is a promising therapeutic method for malignant tumors and has entered the clinical trials. As a binary cellular accurate therapy, BNCT relies on tumor-targeting boron delivery. It is intriguing for boron delivery design that selective recognization, target, and accumulation are based on specific or differential expression receptors on the tumor cell surface. Several delivery strategies targeting other subcellular organelles have also emerged. Here, we summarized the selection, challenges, and improvement of boron targeting delivery methods in small molecule boron drugs and boron-containing nanoparticles. In the future, new technologies, new methods, and new ideas include target receptors finding via omics, ligands optimization via machine learning, and establishment of modular boron cores based on receptors and ligands libraries, thereby provide great convenience for the development of molecular-targeted boron drugs and multi-targeted boron drugs.

Boron neutron capture therapy (BNCT) is a potential radiation therapy modality for cancer, and tumor-targeted stable boron-10 (10B) delivery agents are an important component of BNCT. Currently, two low-molecular-weight boron-containing compounds, sodium mercaptoundecahydro-closo-dodecaborate (BSH) and boronophenylalanine (BPA), are mainly used in BNCT. Although both have suboptimal tumor selectivity, they have shown some therapeutic benefit in patients with high-grade glioma and several other tumors. To improve the efficacy of BNCT, great efforts have been devoted for the development of new boron delivery agents with better uptake and favorable pharmacokinetic profiles. This article reviews the application and research progress of boron nanomaterials as boron carriers in boron neutron capture therapy and hopes to stimulate people’s interest in nanomaterial-based delivery agents by summarizing various kinds of boron nanomaterial patents disclosed in the past decade.

Abstract Glioblastoma is the most common brain primary malignant tumor with the highest mortality. Boron neutron capture therapy (BNCT) can efficiently kill cancer cells on the cellular scale, with high accuracy, short course and low side-effects, which is regarded as the most promising therapy for malignant brain tumors like glioma. As the keypoint of BNCT, all boron delivery agents currently in clinical use are beset by insufficient tumor uptake, especially in the tumor nucleus, which limits the clinical application of BNCT. In this study, nuclear targeting of boron is achieved by DOX-CB, consisting of doxorubicin (DOX) and carborane (CB) utilizing the nuclear translocation property of DOX. The nucleus of GL261 cells takes up almost three times the concentration of boron required for BNCT. To further kill glioma and inhibit recurrence, a new multifunctional nanoliposome delivery system DOX-CB@lipo-pDNA-iRGD is constructed. It combines DOX-CB with immunotherapy strategy of blocking macrophage immune checkpoint pathway CD47-SIRPα by CRISPR-Cas9 system, coupling BNCT with immunotherapy simultaneously. Compared with clinical drug Borocaptate Sodium (BSH), DOX-CB@lipo-pDNA-iRGD significantly enhances the survival rate of tumor-bearing mice, reduces tumor stemness, and improves the prognosis. The excellent curative effect of this nanoliposome delivery system provides an insight into the combined treatment of BNCT. Graphical Abstract

Multidisciplinary therapy centered on radical surgery for resectable pancreatic cancer is expected to prolong prognosis, but relies on CA19-9 biomarker levels to determine treatment strategy. Boron neutron capture therapy (BNCT) is a chemoradiotherapy using tumor hyperaccumulator boron drugs and neutron irradiation. The purpose of this study is to investigate novel boron drug agents for BNCT for pancreatic cancer. Bioinformatics was used to evaluate the uptake of current boron amino acid (BPA) drugs for BNCT into pancreatic cancer. The expression of the amino acid transporter LAT1, a BPA uptake transporter, was low in pancreatic cancer and even lower in high CA19-9 pancreatic cancer. In contrast, the glucose transporter was high in high CA19-9 pancreatic cancers and inversely correlated with LAT1 expression. Considering the low EPR effect in pancreatic cancer, we synthesized a small molecule Glucose-BSH, which is boron BSH bound to glucose, and confirmed its specific uptake in pancreatic cancer. uptake of Glucose-BSH was confirmed in an environment compatible with the tumor microenvironment. The therapeutic efficacy and safety of Glucose-BSH by therapeutic neutron irradiation were confirmed with BNCT. We report Glucose-BSH boron drug discovery study of a Precision Medicine BNCT with application to high CA19-9 pancreatic cancer. • Boron neutron capture therapy (BNCT) is a chemoradiotherapy using boron agents and neutron irradiation; the cancer accumulation capacity of boron agents is the key to its application in pancreatic cancer. • We successfully developed a boron-based drug targeting a glucose transporter that is highly expressed in pancreatic cancer. • BNCT using the sugar-binding boron drug developed in this study is a novel therapy as BNCT targeting pancreatic cancer with high CA19-9 levels. [ABSTRACT FROM AUTHOR]

Glioblastoma is the most common brain primary malignant tumor with the highest mortality. Boron neutron capture therapy (BNCT) can efficiently kill cancer cells on the cellular scale, with high accuracy, short course and low side-effects, which is regarded as the most promising therapy for malignant brain tumors like glioma. As the keypoint of BNCT, all boron delivery agents currently in clinical use are beset by insufficient tumor uptake, especially in the tumor nucleus, which limits the clinical application of BNCT. In this study, nuclear targeting of boron is achieved by DOX-CB, consisting of doxorubicin (DOX) and carborane (CB) utilizing the nuclear translocation property of DOX. The nucleus of GL261 cells takes up almost three times the concentration of boron required for BNCT. To further kill glioma and inhibit recurrence, a new multifunctional nanoliposome delivery system DOX-CB@lipo-pDNA-iRGD is constructed. It combines DOX-CB with immunotherapy strategy of blocking macrophage immune checkpoint pathway CD47-SIRPα by CRISPR-Cas9 system, coupling BNCT with immunotherapy simultaneously. Compared with clinical drug Borocaptate Sodium (BSH), DOX-CB@lipo-pDNA-iRGD significantly enhances the survival rate of tumor-bearing mice, reduces tumor stemness, and improves the prognosis. The excellent curative effect of this nanoliposome delivery system provides an insight into the combined treatment of BNCT. [ABSTRACT FROM AUTHOR]

[Display omitted] Boron neutron capture therapy (BNCT), as an innovative radiotherapy technology, has demonstrated remarkable outcomes when compared to conventional treatments in the management of recurrent and refractory brain tumors. However, in BNCT of brain tumors, the blood–brain barrier is a main stumbling block for restricting the transport of boron drugs to brain tumors, while the tumor targeting and retention of boron drugs also affect the BNCT effect. This review focuses on the recent development of strategies for delivering boron drugs crossing the blood–brain barrier and targeting brain tumors, providing new insights for the development of efficient boron drugs for the treatment of brain tumors. [ABSTRACT FROM AUTHOR]

• BNCT has more potential to effectively target multicentric deposits of tumors. • This review focuses on tumor-targeting boron delivery agents developed recently. • This review provides a summary and critical perspective of boron delivery agents. Boron neutron capture therapy (BNCT) is a potential cancer radiotherapeutic modality, which takes advantage of the neutron capture response that occurs when boron (10B) is struck by low-energy thermal neutrons, triggering a nuclear fission reaction that ultimately causes cell death. Because the fatal radiation is restricted to approximately a single cell diameter, only cells with significant boron accumulation that are in the neutron field will be destroyed. Tumor-targeted 10B delivery agents are an essential component of BNCT. Currently, two low molecular weight boron-containing compounds, sodium mercaptoundecahydro-closo-dodecaborate (BSH) and borylphenylalanine (BPA), are mainly used in BNCT. Although both have suboptimal tumor selectivity, they have shown some therapeutic effect in patients with high-grade gliomas and several other kinds of tumors. In order to improve the efficacy of BNCT, significant effort has been devoted to developing new boron delivery agents that possess better uptake and favorable pharmacokinetic characteristics for clinical use. This review focuses on various boron delivery agents that have been developed over the past 40 years, including boron-containing amino acids, boron-containing compound conjugated-nucleosides, porphyrin derivatives, peptides, monoclonal antibodies, and different types of nanomaterials for 10B delivery. The principles underlying BNCT and the clinical trials with BNCT are briefly introduced in the first part of this review. In the second part, we provide a detailed overview of various boron delivery agents and discuss their merits and limitations. Additionally, the preclinical outcomes of these agents are included in this review and the most promising delivery agents are highlighted and compared. In summary, this article provides an overview of boron delivery agents, and critically analyzes their clinical prospects, from the view of medicinal chemists and nuclear medicine physicians. [ABSTRACT FROM AUTHOR]