Boron neutron capture therapy for oral precancer: proof of principle in an experimental animal model.

OBJECTIVES: Field-cancerized tissue can give rise to second primary tumours, causing therapeutic failure. Boron neutron capture therapy (BNCT) is based on biological targeting and would serve to treat undetectable foci of malignant transformation. The aim of this study was to optimize BNCT for the integral treatment for oral cancer, with particular emphasis on the inhibitory effect on tumour development originating in precancerous conditions, and radiotoxicity of different BNCT protocols in a hamster cheek pouch oral precancer model. MATERIALS AND METHODS: Groups of cancerized hamsters were locally exposed to single or double (2 or 4 weeks apart) applications of BNCT at different dose levels, mediated by the boron compounds boronophenylalanine (BPA) or BPA and decahydrodecaborate (GB-10) administered jointly. Cancerized, sham-irradiated hamsters served as controls. Clinical status, tumour development from field-cancerized tissue and mucositis were followed for 8 months. RESULTS: A double application (4 weeks apart) of BNCT mediated by GB-10+ BPA at a total dose of 10 Gy in two 5-Gy doses rendered the best therapeutic advantage (63-100% inhibition of tumour development from field-cancerized tissue), minimizing dose-limiting mucositis. CONCLUSION: BNCT can be optimized for the integral treatment for head and neck cancer, considering the implications for field-cancerized tissue.

2-Pyrrolidinylideneureas, a new class of central nervous system agents.

A series of N-aryl-N'-(1-methyl-2-pyrrolidinylidene)ureas was prepared and screened for pharmacological activity. Congeners possessing either phenyl or phenyl substituted with 4-nitro, 3-bromo, 3-chloro, 3-fluoro, and 3-methyl groups were found to demonstrate anxiolytic activity. 2,6-Disubstitution of the phenyl ring with methyl, chloro, and bromo imparted potent muscle-relaxant properties which appear to be centrally mediated. A significant separation of the anxiolytic and muscle-relaxant properties from other CNS activities, e.g., anticonvulsant, sedative, and hypnotic, was achieved.

Dosimetry and radiobiology at the new RA-3 reactor boron neutron capture therapy (BNCT) facility: application to the treatment of experimental oral cancer.

The National Atomic Energy Commission of Argentina (CNEA) constructed a novel thermal neutron source for use in boron neutron capture therapy (BNCT) applications at the RA-3 research reactor facility located in Buenos Aires. The aim of the present study was to perform a dosimetric characterization of the facility and undertake radiobiological studies of BNCT in an experimental model of oral cancer in the hamster cheek pouch. The free-field thermal flux was 7.1 x 10(9) n cm(-2)s(-1) and the fast neutron flux was 2.5 x 10(6) n cm(-2)s(-1), indicating a very well-thermalized neutron field with negligible fast neutron dose. For radiobiological studies it was necessary to shield the body of the hamster from the neutron flux while exposing the everted cheek pouch bearing the tumors. To that end we developed a lithium (enriched to 95% in (6)Li) carbonate enclosure. Groups of tumor-bearing hamsters were submitted to BPA-BNCT, GB-10-BNCT, (GB-10+BPA)-BNCT or beam only treatments. Normal (non-cancerized) hamsters were treated similarly to evaluate normal tissue radiotoxicity. The total physical dose delivered to tumor with the BNCT treatments ranged from 6 to 8.5 Gy. Tumor control at 30 days ranged from 73% to 85%, with no normal tissue radiotoxicity. Significant but reversible mucositis in precancerous tissue surrounding tumors was associated to BPA-BNCT. The therapeutic success of different BNCT protocols in treating experimental oral cancer at this novel facility was unequivocally demonstrated.

The design, synthesis and physical chemical properties of novel human vasopressin V2-receptor antagonists optimized for parenteral delivery.

Ionizable groups were introduced onto the 10,11-dihydro-5H-pyrrolo[2,1-c][1,4]benzodiazepine scaffold of the vasopressin V2-antagonist WAY-VPA-985 in the search for molecules optimized for parenteral formulation. The synthesis and structure activity relationships (SAR) are presented together with solubility data in a model parenteral system. The amine, WAY-140288 (4f), was chosen for further development. p6