Preclinical evaluation and PET imaging of 18F-labeled Mel-14 F(ab')2 fragment in normal dogs.

The F(ab')2 fragment of monoclonal antibody Mel-14, reactive with human melanomas and gliomas, was labeled with 18F using two acylation agents, N-succinimidyl 8-[(4'-[18F]fluorobenzyl)amino]suberate (SFBS) and N-succinimidyl 4-[18F]fluorobenzoate (SFB). The immunoreactivity and affinity for Mel-14 F(ab')2 labeled using the two methods were similar. As a prelude to human clinical evaluation, PET imaging, tissue distribution and pharmacokinetic measurements were performed in two groups of normal foxhounds.

PET imaging of osteosarcoma in dogs using a fluorine-18-labeled monoclonal antibody Fab fragment.

Unlabelled: Four dogs with histologically confirmed osteogenic sarcoma were studied with PET following intravenous injection of the 18F-labeled Fab fragment of TP-3, a monoclonal antibody specific for human and canine osteosarcomas.

Methods: The antibody fragment was labeled using the N-succinimidyl 8-[(4'-[18F]fluorobenzyl)amino]suberate acylation agent. Blood clearance of activity was biphasic in all dogs but half-times were variable (T1/2 beta = 2-13 hr).

Radioimmunotherapy of neoplastic meningitis in rats using an alpha-particle-emitting immunoconjugate.

Because of their short range and high linear energy transfer, alpha-particles may be particularly effective in the treatment of neoplastic meningitis. Monoclonal antibody 81C6 was labeled with alpha-particle-emitting 211At using N-succinimidyl3-[211At]astatobenzoate, and the efficacy and toxicity of this immunoconjugate were evaluated in an athymic rat model. Animals were given injections via a chronic indwelling catheter with 5 x 10(5) TE-671 human rhabdomyosarcoma cells and treated 8 days later with single intrathecal doses of either saline or 4-18 microCi of 211At-labeled specific 81C6 antibody or isotype-matched control 211At-labeled 45.

Improved synthesis of N-succinimidyl 4-[18F]fluorobenzoate and its application to the labeling of a monoclonal antibody fragment.

Our previously reported method for the 18F labeling of antibodies using N-succinimidyl 4-[18F]fluorobenzoate (SFB) involved a rather long synthesis time. Here we present an improved method for the synthesis of SFB which reduces the synthesis time by about 45 min. A reaction time of 5-8 min (versus 25 min for the original procedure) was sufficient in the fluorination step to form 4-[18F]fluorobenzaldehyde in high yield.

Generation and characterization of a mouse/human chimeric antibody directed against extracellular matrix protein tenascin.

The murine anti-tenascin monoclonal antibody 81C6, following iodination, has been shown to be an efficient localizing and therapeutic agent in both subcutaneous and intracranial human glioma xenograft models in athymic mice and rats. Similarly, effective monoclonal antibody 81C6 localization has been demonstrated in glioma patients, and Phase I trials with the intact murine IgG2b kappa molecule are currently in progress. In order to maximize the potential for repeated administration by minimizing murine Fc-mediated immunogenicity and reducing Fc-mediated immune effects, we created murine 81C6 variable region/human IgG2 chimeric monoclonal antibodies by the molecular cloning of the variable region genes of mouse 81C6 and their genetic linkage to human constant region exons.

Meta-[211At]astatobenzylguanidine: further evaluation of a potential therapeutic agent.

Meta-[211At]astatobenzylguanidine ([211At]MABG) is an astatinated analogue of meta-iodobenzylguanidine (MIBG) that could be of value for therapeutic applications. The initial goal of this study was to determine whether [211At]MABG is taken up, like MIBG, by a specific uptake-I mechanism. Norepinephrine and desipramine (DMI) decreased [211At]MABG uptake in SK-N-SH human neuroblastoma cells.

Carrier-free 131I-meta-iodobenzylguanidine: comparison of production from meta-diazobenzylguanidine and from meta-trimethylsilylbenzylguanidine.

Meta-iodobenzylguanidine (MIBG) is a drug which is selectively accumulated by the uptake-1 process in adrenergic tissues. When labelled with 131I, it may be used for the targetted radiotherapy of tumours such as phaeochromocytoma and neuroblastoma. This paper describes the preparation of carrier-free 131I-MIBG by radioiodination of meta-diazobenzylguanidine, and compares this process with one involving iododesilylation of meta-trimethylsilylbenzylguanidine.

Mouse/human chimeric Me1-14 antibody: genomic cloning of the variable region genes, linkage to human constant region genes, expression, and characterization.

Murine monoclonal antibody Me1-14, which recognizes an epitope on chondroitin proteoglycan sulfate expressed in malignant glioma and melanoma, has been used for radioimmunolocalization and therapy both in animal models and in patients. Here, we report the generation, characterization, and in vivo biodistribution of mouse/human chimeric Me1-14. Rearranged immunoglobulin genes from the Me1-14 hybridoma were identified by Southern blot analysis.

Pinhole collimation for ultra-high-resolution, small-field-of-view SPECT.

The objective of this investigation was to evaluate small-field-of-view, ultra-high-resolution pinhole collimation for a rotating-camera SPECT system that could be used to image small laboratory animals. Pinhole collimation offers distinct advantages over conventional parallel-hole collimation when used to image small objects. Since geometric sensitivity increases markedly for points close to the pinhole, small-diameter and high-magnification pinhole geometries may be useful for selected imaging tasks when used with large-field-of-view scintillation cameras.

Monoclonal antibody F(ab')2 fragment labeled with N-succinimidyl 2,4-dimethoxy-3-halobenzoates: in vivo comparison of iodinated and astatinated fragments.

N-Succinimidyl 3-[211At]astato-2, 4-dimethoxybenzoate (SADMB) was prepared from a trialkylstannyl precursor in about 70-75% yield. With either trimethyl or tri-n-butylstannyl precursor, no temporal effect was found in the astatodestannylation yield. However, the methyl analog gave slightly better yield which was found to be not statistically significant.

Synthesis and preliminary evaluation of para- and meta-[18F]fluorobenzylguanidine.

meta-[18F]Fluorobenzylguanidine ([18F]MFBG) and para-[18F]fluorobenzylguanidine ([18F]PFBG) were synthesized in three steps beginning with a fluoro for nitro exchange reaction on 3- and 4-nitrobenzonitrile, respectively. Overall radiochemical yields were 10-15% for [18F]MFBG and 50-55% for [18F]PFBG in a total synthesis time of 60 min. However, impurities interfered with the binding of the product to target cells.

Radioiodination of a monoclonal antibody using N-succinimidyl 5-iodo-3-pyridinecarboxylate.

The potential utility of N-succinimidyl 5-iodo-3-pyridinecarboxylate (SIPC) for the radioiodination of monoclonal antibodies was investigated. Paired-label studies were performed using the anti-tenascin antibody 81C6 in athymic mice bearing subcutaneous D-54 MG human glioma xenografts. Radiolabeling was also done using N-succinimidyl 3-iodobenzoate (SIB).

Measuring astatine-211 distributions with SPECT.

We have investigated standard SPECT techniques (rotating gamma cameras, multi-hole collimators, and filtered backprojection reconstruction) for imaging astatine-211 distributions. Since 211At emits alpha particles, this nuclide has potential for use in radiotherapy. The capability of imaging this nuclide would allow in vivo evaluation of the distribution and stability of potential 211At-labelled radiotherapeutic agents.

Distribution and dosimetry of I-123-labeled monoclonal antibody 81C6 in patients with anaplastic glioma.

Rationale And Objectives: Monoclonal antibody 81C6 reacts with the extracellular matrix antigen, tenascin, present on gliomas and other tumors, as well as several normal tissues, including spleen and liver tissue. Single photon emission computed tomography (SPECT) and I-123-labeled 81C6 at various protein doses were used to maximize tumor to normal tissue uptake ratios.

Methods: The distribution of I-123-labeled monoclonal antibody 81C6 was determined in 16 patients with recurrent gliomas, using SPECT: Between 3.

N-succinimidyl 4-methyl-3-(tri-n-butylstannyl)benzoate: synthesis and potential utility for the radioiodination of monoclonal antibodies.

N-succinimidyl 4-methyl-3-(tri-n-butylstannyl)benzoate (MATE) was synthesized in two steps from 4-methyl-3-iodobenzoic acid. Radioiododestannylation of MATE proceeded more slowly than N-succinimidyl 3-(tri-n-butylstannyl)benzoate (ATE), but for reaction periods of 10 min or more, identical yields were obtained. Paired-label biodistribution studies were performed in mice with an intact monoclonal antibody and an F(ab')2 fragment labeled using MATE, ATE and Iodogen.

No-carrier-added synthesis of meta-[131I]iodobenzylguanidine.

No-carrier-added meta-[131I]iodobenzylguanidine ([131I]MIBG) was prepared starting with two different metallated precursors. Attempted preparation of 3-(tri-n-butylstannyl)benzylguanidine was not successful. An alternate two-step strategy using 3-(tri-n-butylstannyl)benzylamine could be used to prepare radio-iodinated [131I]MIBG in an overall radiochemical yield of 30-33%.

Radioiodination of proteins using N-succinimidyl 4-hydroxy-3-iodobenzoate.

N-Succinimidyl 4-hydroxy-3-[131I]iodobenzoate ([131I]SHIB) was synthesized from 4-hydroxybenzoic acid in two steps. The overall radiochemical yield was 40-56%. A monoclonal antibody (mAb) was labeled in 10-15% yield by reaction with [131I]SHIB.

1-(m-[211At]astatobenzyl)guanidine: synthesis via astato demetalation and preliminary in vitro and in vivo evaluation.

No-carrier-added 1-(m-[211At]astatobenzyl)guanidine ([211At]MABG) was synthesized by astato demetalation using two different routes. The overall yield for the two-step approach from 3-(tri-n-butylstannyl)benzylamine was 13%. N-Chlorosuccinimide-mediated astato desilylation of 1-[3-(trimethylsilyl)benzyl]guanidine in acetic acid gave poor yields.

Localization of fluorine-18-labeled Mel-14 monoclonal antibody F(ab')2 fragment in a subcutaneous xenograft model.

Positron emission tomography is an imaging method that might improve the effectiveness of radioimmunoscintigraphy and might provide more accurate estimates of monoclonal antibody dosimetry prior to therapy. Because of its widespread availability, 2-h half-life 18F could be a useful nuclide for labeling monoclonal antibody fragments, provided that adequate tumor uptake and satisfactory tumor:normal tissue ratios could be achieved rapidly. In this study, the tissue distribution of 18F-labeled Mel-14 F(ab')2, a monoclonal antibody reactive with gliomas, was evaluated in a s.

Immunoreactivity, pharmacokinetics and bone marrow dosimetry of intrathecal radioimmunoconjugates.

Ten patients with neoplastic meningitis were treated with a variety of 131I-monoclonal antibody (MAb) conjugates, chosen to bind to their particular malignancy. Pharmacokinetic studies revealed that MAbs leave the ventricular compartment, enter the sub-arachnoid space and then pass into the blood. Once the MAbs enter the blood compartment, their clearance is determined by factors such as circulating anti-mouse Ig and circulating antigens.

Fluorine-18-labeled monoclonal antibody fragments: a potential approach for combining radioimmunoscintigraphy and positron emission tomography.

Monoclonal antibody fragments labeled with 18F could be useful for PET if selective tumor uptake could be achieved within a few half-lives of this nuclide. To evaluate this possibility, the F(ab')2 fragment of Mel-14, an antibody reactive with gliomas and other tumors, was labeled by reaction with N-succinimidyl-4-[18F]fluorobenzoate. The in-vitro binding properties of 18F-labeled Mel-14 F(ab')2 were nearly identical to those observed when this F(ab')2 was labeled by reaction with N-succinimidyl-4-[125I]iodobenzoate (18F, affinity constant = (6.

Labeling proteins with fluorine-18 using N-succinimidyl 4-[18F]fluorobenzoate.

Two methods were investigated for the no-carrier-added synthesis of N-succinimidyl 4-[18F]fluorobenzoate (S[18F]FB). The first, an attempted nucleophilic aromatic substitution by [18F]fluoride on N-succinimidyl 4-nitrobenzoate was unsuccessful. The second method involved three steps; [18F]fluoride for trimethylammonium substitution on 4-formyl-N,N,N-trimethylanilinium triflate, oxidation to 4-[18F]fluorobenzoic acid, followed by reaction with N-hydroxysuccinimide and dicyclohexylcarbodiimide to form S[18F]FB.

Fluorine-18-antimyosin monoclonal antibody fragments: preliminary investigations in a canine myocardial infarct model.

The purpose of this study was to determine in a canine model whether selective myocardial infarct uptake of 18F-labeled antimyosin monoclonal antibody fragments could be achieved in a time frame compatible with the short half-life of this nuclide. Antimyosin monoclonal antibody fragments were labeled with 18F using a succinimidyl [18F]fluorobenzylamine ester acylation agent. Six dogs had myocardial infarction induced by coronary artery occlusion and were reperfused prior to the intravenous administration of 0.

4-Fluorobenzylamine and phenylalanine methyl ester conjugates of 2-nitroimidazole: evaluation as hypoxic cell radiosensitizers.

We have synthesized two 2-nitroimidazole derivatives and evaluated their hypoxic radiosensitization properties. The first, a 4-fluorobenzylamine conjugate of 2-nitroimidazole (PK-110), was designed so that it could also be labeled with the F-18 and used for positron emission tomographic imaging of hypoxia. The second, the L-phenylalanine methyl ester conjugate of 2-nitroimidazole (PK-130), was designed in an attempt to exploit amino acid transport channels to enhance drug transport into the tumor.