A technique to prepare boronated B72.3 monoclonal antibody for boron neutron capture therapy

Radioiodination of ammonio-closo-monocarborane, 1-H3N-1-CB11H11. Aspects of labelling chemistry in aqueous solution using Chloramine-T

The aim of this study was to investigate the use of electrophilic radioiodination in the labelling of closo-monocarborane(-1). Ammonio-closo-monocarborane (ACMC, 1NH31CB11H11) was labelled with 125I using Chloramine-T as an oxidant. Radio-TLC was used for analysis. Influence of substrate amount, oxidant concentration, and pH of the reaction media on the labelling yield was studied. A labelling yield of 80%-90% was obtained. The results of the study indicate feasibility to use derivatives of closo-monocarborane(-1) as a pendant group for indirect radioiodination of proteins, and for studying pharmacokinetics of boron-rich compounds for BNCT.

Application of drug delivery system to boron neutron capture therapy for cancer

BACKGROUND

Tumor cell destruction in boron neutron capture therapy (BNCT) is due to the nuclear reaction between (10)B and thermal neutrons ((10)B + (1)n --> (7)Li + (4)He (alpha) + 2.31 MeV (93.7 %)/2.79 MeV (6.3 %)). The resulting lithium ions and alphaparticles are high linear energy transfer (LET) particles which give a high biological effect. Their short range in tissue (5 - 9 mum) restricts radiation damage to those cells in which boron atoms are located at the time of neutron irradiation. BNCT has been applied clinically for the treatment of malignant brain tumors, malignant melanoma, head and neck cancer and hepatoma. Sodium mercaptoundecahydro-dodecaborate (Na(2)(10)B(12)H(11)SH: BSH) and borono-phenylalanine ((10)BPA) are currently being used in clinical treatments. These low molecule compounds are easily cleared from cancer cells and blood, so high accumulation and selective delivery of boron compounds into tumor tissues and cancer cells are most important to achieve effective BNCT and to avoid damage to adjacent healthy cells.

OBJECTIVE

In order to achieve the selective delivery of boron atoms to cancer cells, a drug delivery system (DDS) is an attractive intelligent technology for targeting and controlled release of drugs.

METHODS

We performed literature searches related to boron delivery systems in vitro and in vivo.

RESULTS

We describe several DDS technologies for boron delivery to cancer tissues and cancer cells from the past to current status. We are convinced that it will be possible to use liposomes, monoclonal antibodies and WOW emulsions as boron delivery systems for BNCT clinically in accordance with the preparation of good commercial product (GCP) grade materials.

Linkage of boronated polylysine to glycoside moieties of polyclonal antibody; boronated antibodies as potential delivery agents for neutron capture therapy

Among the ways to deliver comparatively large amounts of boron to cells in vitro for boron neutron capture studies is the linkage of a boronated macromolecule such as polylysine to an antibody. In order to reduce interference with immunoreactivity, boronated polylysine (BPL) was linked to oligosaccharide moieties on the IgG molecule distant from the antibody combining sites. The resultant bioconjugate was chromatographically separated from free BPL and unconjugated antibody using a Sephacryl S300 column. The total measured boron per BPL-IgG conjugate, determined by direct current plasma atomic emission spectroscopy, was estimated to be approximately 6 x 10(3) atoms. This, together with molecular weight estimations, indicated conjugation of about 3 polylysines to each IgG molecule. Immunoreactivity of the conjugate was found to be the same as that of the unconjugated polyclonal antibody. This was based on its concentration dependent interference with immunometric reactions for an antigen (TSH), whereas heat inactivated or non-specific antibody had no such inhibitory effects. The results support the hypothesis that the binding affinity of the conjugate for antigen was preserved after its linkage to BPL under the conditions described. The methodology described in this report may have applicability for the preparation of boronated antibodies as delivery agents for BNCT.