Proposal of recommended experimental protocols for in vitro and in vivo evaluation methods of boron agents for neutron capture therapy

Boron neutron capture therapy with pteroyl-closo-dodecaborate-conjugated 4-(p-iodophenyl)butyric acid (PBC-IP) for a head and neck squamous cell carcinoma (SAS) model mice

Boron neutron capture therapy (BNCT) is an attractive therapeutic approach for treating refractory cancers. Currently, 4-borono-L-phenylalanine (BPA) is the only boron carrier approved for BNCT, specifically for unresectable, locally advanced, or recurrent head and neck cancers in Japan. However, efficacy of BPA relies on the L-type amino acid transporter (LAT1), which is highly expressed in many cancers, limiting its broader application. In this study, we investigated the potential of a novel boron carrier, pteroyl-closo-dodecaborate-conjugated 4-(p-iodophenyl)butyric acid (PBC-IP), designed to the folate receptors (FRs), as an alternative for BNCT in head and neck cancers. PBC-IP was injected into human head and neck squamous cell carcinoma SAS xenograft mice to assess its biodistribution and therapeutic efficacy compared to BPA. Our results showed that PBC-IP achieved selective tumor accumulation, although the boron concentration in tumors was lower than that of BPA (5 μg [10B]/g vs. 15 μg [10B]/g, respectively). PBC-IP underwent significant hepatic metabolism. BNCT treatment with PBC-IP suppressed tumor growth in mice, whereas BPA showed superior efficacy, nearly eliminating tumors. Importantly, no significant toxicity was observed in either group. These findings suggest that while PBC-IP exhibits some potential for BNCT targeting FR-expressing tumors, BPA remains the more effective option for head and neck cancer.

Comparison of Radionuclide Drug Conjugates With Boron Neutron Capture Therapy: An Overview of Targeted Charged Particle Radiation Therapy

Targeted charged alpha- and beta-particle therapies are currently being used in clinical radiation treatments as newly developed methods for either killing or controlling tumor cell growth. The alpha particles can be generated either through a nuclear decay reaction or in situ by a nuclear fission reaction such as the boron neutron capture reaction. Different strategies have been employed to improve the selectivity and delivery of radiation dose to tumor cells based on the source of the clinically used alpha particles. As a result, the side effects of the treatment can be minimized. The increasing attention and research efforts on targeted alpha-particle therapy have been fueled by exciting results of both academic research and clinical trials. It is highly anticipated that alpha-particle therapy will improve the efficacy of treating malignant tumors. In this overview, we compare radionuclide drug conjugates (RDC) with boron neutron capture therapy (BNCT) to present recent developments in targeted alpha-particle therapy.

Boron Nanocomposites for Boron Neutron Capture Therapy and in Biomedicine: Evolvement and Challenges

Cancer remains a major concern for human health worldwide. To fight the curse of cancer, boron neutron capture therapy is an incredibly advantageous modality in the treatment of cancer as compared to other radiotherapies. Due to tortuous vasculature in and around tumor regions, boron (10B) compounds preferentially house into tumor cells, creating a large dose gradient between the highly mingled cancer cells and normal cells. Epithermal or thermal neutron bombardment leads to tumor-cell-selective killing due to the generation of heavy particles yielded from in situ fission reaction. However, the major challenges for boron nanocomposites' development have been from the synthesis part as well as the requirement for selective cancer targeting and the delivery of therapeutic concentrations of boron (10B) with nominal healthy tissue accumulation and retention. To circumvent the above challenges, this review discusses boride nanocomposite design, safety, and biocompatibility for biomedical applications for general public use. This review sparks interest in using boron nanocomposites as boron neutron capture therapy agents and repurposing them in comorbidity treatments, with future scientific challenges and opportunities, with a hope to accelerate the stimulus of developing possible boron composite nanomedicine research and applications worldwide.

Poly(vinyl alcohol) potentiating an inert d-amino acid-based drug for boron neutron capture therapy

Since the discovery of d-amino acids, they have been considered inactive and have not been used as potent drugs. Here, we report that simple mixing with poly(vinyl alcohol) (PVA) unleashed latent potentials of d-amino acids in boron neutron capture therapy (BNCT). PVA formed boronate esters with seemingly useless boronated d-amino acids and induced tumor-associated amino acid transporter-superselective internalization and prolonged intracellular retention, accomplishing complete cure of tumors. The superselective internalization was achieved by switching the internalization pathway from ineffective pass through the transporter to the transporter-mediated endocytosis. The acidic environment in the endo-/lysosome dissociated the boronate esters and elicited the stealthiness of the drugs, preventing their externalization and prolonging intracellular retention time. In a subcutaneous tumor model, this system accomplished surprisingly high tumor-selective accumulation that could not be achieved by conventional approaches and induced drastic BNCT effects. PVA may be a unique material to unlock potentials of seemingly inert molecules.

Simple Cytosolic and Nuclear Introduction of Boron Compounds Using Cationic Lipids to Enhance Cancer Cell-Killing Activity in Boron Neutron Capture Therapy

Boron neutron capture therapy (BNCT), a type of nuclear capture-based radiotherapy, has received extensive attention because of its strong anticancer effects, especially in head and neck cancers. This therapy was approved for clinical use in 2020 in Japan. This study demonstrated a technique that effectively uses the electrostatic interactions of negatively charged borane cage (polyhedral borane anion) of disodium mercaptoundecahydro-closo-dodecaborate (BSH) and positively charged cationic lipids or arginine-rich cell-penetrating peptides as carriers to enhance the efficiency of cellular uptake. Mixing of fluorescein isothiocyanate (FITC)-labeled BSH (FITC-BSH) with the cationic lipids led to increased cytosolic release and nuclear accumulation of FITC-BSH, resulting in superior cancer cell-killing activity following thermal neutron irradiation. This simple technique and our experimental results provide essential insights for the further development of BNCT.

Unveiling bisphenol A toxicity: human health impacts and sustainable treatment strategies

INTRODUCTION

The widespread presence of bisphenol-A (BPA) in consumer goods like water bottles and eyeglass frames raises serious concerns about the chemical's ability to accumulate in human tissues. Molecular filtration and activated carbon adsorption are two of the many BPA treatment technologies that have emerged in response to these issues; both are essential in the removal or degradation of BPA from water sources and industrial effluents.

CONTENT

To secure the long-term health and environmental advantages of BPA treatment approaches, sustainable development is essential. Both the efficient elimination or destruction of BPA and the reduction of the treatment operations' impact on the environment are important components of a sustainable approach. Different search engines like Pub-Med, MEDLINE, Google Scholar and Scopus are used for these systematic reviews and analyzed accordingly. This can be accomplished by making treatment facilities more energy efficient and using environmentally friendly materials. Greener ways to deal with BPA pollution are on the horizon, thanks to innovative techniques like bioremediation and improved oxidation processes. Reducing dependence on conventional, resource-intensive procedures can be achieved by investigating the use of bio-based materials and natural adsorbents in treatment processes.

SUMMARY AND OUTLOOK

This review article tackling the health and environmental concerns raised by BPA calls for an integrated strategy that incorporates sustainable development principles and technology progress. We can reduce the negative impacts of BPA contamination, improve environmental stewardship in the long run, and ensure human health by combining cutting-edge treatment technologies with sustainable behaviours.

A simple prediction model for the risk of boron neutron capture therapy-induced nausea and vomiting in head and neck cancer

BACKGROUND AND PURPOSE

Head and neck cancer patients undergoing boron neutron capture therapy (BNCT) often experience BNCT-induced nausea and vomiting (BINV). This study aimed to construct a BINV risk prediction model.

MATERIALS AND METHODS

In this retrospective study, 237 patients were randomly divided into a training and test cohort. In the training cohort, a univariate analysis was performed to identify factors associated with BINV. Multivariate analysis was used to identify factors and calculate coefficients for the model. The Hosmer-Lemeshow test was used to assess the goodness of fit, and receiver operating characteristic curves were plotted to evaluate the accuracy of the model. For both the training and test cohort, the predictive model was used to generate the scores and calculate the sensitivity and specificity.

RESULTS

The incidence of nausea and vomiting was 50% and 18%, respectively. Female sex, younger age, non-squamous cell carcinoma, no prior chemotherapy, and beam entry from the face/lateral region were associated with the occurrence of BINV. The prediction model showed a good fit (P = 0.96) and performance (area under the curve = 0.75). The sensitivity and specificity were 83% and45 % for the training cohort (n = 193) and 86% and 59% for the test cohort (n = 44), respectively.

CONCLUSION

We developed a simple model that predicts BINV. This will enable appropriate care to be implemented based on increased risk to prevent its occurrence.

Evaluation of sodium borocaptate (BSH) and boronophenylalanine (BPA) as boron delivery agents for neutron capture therapy (NCT) of cancer: an update and a guide for the future clinical evaluation of new boron delivery agents for NCT

Boron neutron capture therapy (BNCT) is a cancer treatment modality based on the nuclear capture and fission reactions that occur when boron-10, a stable isotope, is irradiated with neutrons of the appropriate energy to produce boron-11 in an unstable form, which undergoes instantaneous nuclear fission to produce high-energy, tumoricidal alpha particles. The primary purpose of this review is to provide an update on the first drug used clinically, sodium borocaptate (BSH), by the Japanese neurosurgeon Hiroshi Hatanaka to treat patients with brain tumors and the second drug, boronophenylalanine (BPA), which first was used clinically by the Japanese dermatologist Yutaka Mishima to treat patients with cutaneous melanomas. Subsequently, BPA has become the primary drug used as a boron delivery agent to treat patients with several types of cancers, specifically brain tumors and recurrent tumors of the head and neck region. The focus of this review will be on the initial studies that were carried out to define the pharmacokinetics and pharmacodynamics of BSH and BPA and their biodistribution in tumor and normal tissues following administration to patients with high-grade gliomas and their subsequent clinical use to treat patients with high-grade gliomas. First, we will summarize the studies that were carried out in Japan with BSH and subsequently at our own institution, The Ohio State University, and those of several other groups. Second, we will describe studies carried out in Japan with BPA and then in the United States that have led to its use as the primary drug that is being used clinically for BNCT. Third, although there have been intense efforts to develop new and better boron delivery agents for BNCT, none of these have yet been evaluated clinically. The present report will provide a guide to the future clinical evaluation of new boron delivery agents prior to their clinical use for BNCT.

Active control of pharmacokinetics using light-responsive polymer-drug conjugates for boron neutron capture therapy

In boron neutron capture therapy (BNCT), boron drugs should exhibit high intratumoral boron concentrations during neutron irradiation, while being cleared from the blood and normal organs. However, it is usually challenging to achieve such tumor accumulation and quick clearance simultaneously in a temporally controlled manner. Here, we developed a polymer-drug conjugate that can actively control the clearance of the drugs from the blood. This polymer-drug conjugate is based on a biocompatible polymer that passively accumulates in tumors. Its side chains were conjugated with the low-molecular-weight boron drugs, which are immediately excreted by the kidneys, via photolabile linkers. In a murine subcutaneous tumor model, the polymer-drug conjugate could accumulate in the tumor with the high boron concentration ratio of the tumor to the surrounding normal tissue (∼10) after intravenous injection while a considerable amount remained in the bloodstream as well. Photoirradiation to blood vessels through the skin surface cleaved the linker to release the boron drug in the blood, allowing for its rapid clearance from the bloodstream. Meanwhile, the boron concentration in the tumor which was not photoirradiated could be maintained high, permitting strong BNCT effects. In clinical BNCT, the dose of thermal neutrons to solid tumors is determined by the maximum radiation exposure to normal organs. Thus, our polymer-drug conjugate may enable us to increase the therapeutic radiation dose to tumors in such a practical situation.

Targeted Boron Neutron Capture Therapy Using Polymalic Acid Derived Nano-Boron to Treat Glioblastoma

Despite extensive efforts, glioblastoma multiforme (GBM), the most malignant brain cancer, continues to pose significant challenges to effective treatment, with limited progress in patient survival over the last three decades. This study addresses shortcomings of conventional therapies, particularly radiotherapy (RT), which faces limitations due to radio-resistance and toxic radiation doses. Boron neutron capture therapy (BNCT) is a promising alternative, delivering targeted radiation to tumor cells with minimal damage to healthy tissue. However, the key challenge lies in achieving sufficient boron uptake selectively in tumor cells. We have developed a novel nanomedicine-based approach, utilizing polymalic acid (PMLA) as a delivery vehicle, carrying multiple boron-10 molecules per nanoconjugate to increase the intracellular concentration of boron-10 for effective boron neutron capture therapy. Our novel nanodrug (Nano-Boron) incorporates isotopically enriched 4-boronophenylalanine (BPA) as a source of boron-10 and Angiopep-2 (AP2) peptide for blood-brain barrier penetration and tumor targeting. The PMLA platform allows for the attachment of a large quantity of boron-10, enhancing the intracellular boron concentration and, consequently, the efficacy of BNCT. This innovative approach holds the potential to address the unmet clinical need in GBM treatment and improve patient survival and quality of life.

Early Stage In Vitro Bioprofiling of Potential Low-Molecular-Weight Organoboron Compounds for Boron Neutron Capture Therapy (BNCT)-Proposal for a Guide

Given the renewed interest in boron neutron capture therapy (BNCT) and the intensified search for improved boron carriers, as well as the difficulties of coherently comparing the carriers described so far, it seems necessary to define a basic set of assays and standardized methods to be used in the early stages of boron carrier development in vitro. The selection of assays and corresponding methods is based on the practical experience of the authors and is certainly not exhaustive, but open to discussion. The proposed tests/characteristics: Solubility, lipophilicity, stability, cytotoxicity, and cellular uptake apply to both low molecular weight (up to 500 Da) and high molecular weight (5000 Da and more) boron carriers. However, the specific methods have been selected primarily for low molecular weight boron carriers; in the case of high molecular weight compounds, some of the methods may need to be adapted.

Targeting the organelle for radiosensitization in cancer radiotherapy

Radiotherapy is a well-established cytotoxic therapy for local solid cancers, utilizing high-energy ionizing radiation to destroy cancer cells. However, this method has several limitations, including low radiation energy deposition, severe damage to surrounding normal cells, and high tumor resistance to radiation. Among various radiotherapy methods, boron neutron capture therapy (BNCT) has emerged as a principal approach to improve the therapeutic ratio of malignancies and reduce lethality to surrounding normal tissue, but it remains deficient in terms of insufficient boron accumulation as well as short retention time, which limits the curative effect. Recently, a series of radiosensitizers that can selectively accumulate in specific organelles of cancer cells have been developed to precisely target radiotherapy, thereby reducing side effects of normal tissue damage, overcoming radioresistance, and improving radiosensitivity. In this review, we mainly focus on the field of nanomedicine-based cancer radiotherapy and discuss the organelle-targeted radiosensitizers, specifically including nucleus, mitochondria, endoplasmic reticulum and lysosomes. Furthermore, the organelle-targeted boron carriers used in BNCT are particularly presented. Through demonstrating recent developments in organelle-targeted radiosensitization, we hope to provide insight into the design of organelle-targeted radiosensitizers for clinical cancer treatment.

Nonclinical pharmacodynamics of boron neutron capture therapy using direct intratumoral administration of a folate receptor targeting novel boron carrier

Background

Boron neutron capture therapy (BNCT) is a precise particle radiation therapy known for its unique cellular targeting ability. The development of innovative boron carriers is crucial for the advancement of BNCT technologies. Our previous study demonstrated the potential of PBC-IP administered via convection-enhanced delivery (CED) in an F98 rat glioma model. This approach significantly extended rat survival in neutron irradiation experiments, with half achieving long-term survival, akin to a cure, in a rat brain tumor model. Our commitment to clinical applicability has spurred additional nonclinical pharmacodynamic research, including an investigation into the effects of cannula position and the time elapsed post-CED administration.

Methods

In comprehensive in vivo experiments conducted on an F98 rat brain tumor model, we meticulously examined the boron distribution and neutron irradiation experiments at various sites and multiple time intervals following CED administration.

Results

The PBC-IP showed substantial efficacy for BNCT, revealing minimal differences in tumor boron concentration between central and peripheral CED administration, although a gradual decline in intratumoral boron concentration post-administration was observed. Therapeutic efficacy remained robust, particularly when employing cannula insertion at the tumor margin, compared to central injections. Even delayed neutron irradiation showed notable effectiveness, albeit with a slightly reduced survival period. These findings underscore the robust clinical potential of CED-administered PBC-IP in the treatment of malignant gliomas, offering adaptability across an array of treatment protocols.

Conclusions

This study represents a significant leap forward in the quest to enhance BNCT for the management of malignant gliomas, opening promising avenues for clinical translation.