Technetium-99m labelling of the IOR CEA 1 monoclonal antibody: evaluation of different methods.
OBJECTIVE
The aim of this study was to investigate the in vivo and in vitro properties of 99mTc labelled monoclonal antibody, IOR CEA 1 when radiolabelled by different methods.


METHODS
To achieve that purpose IOR CEA was directly radiolabelled via 2-mercaptoethanol (2-Me) and stannous ion (SnCl2) reduction and indirectly via the 2-iminothiolane (2-Im) conjugation. The resulting 99mTc-MoAbs were analysed for number of free sulfhydryl groups, chemical and radiochemical purity (checked by HPLC and SDS PAGE), immunoreactivity and biological distribution in mice.


RESULTS
Experimental results indicated a similar radiochemical purity and immunoreactivity for direct labelling methods and a decrease of both for 2-Im method. 2-Me antibody reduction led to a high antibody fragmentation as indicated by non-denaturing SDS PAGE analysis. Nevertheless SnCl2 and 2-Im labels revealed lower in vivo stability.


CONCLUSIONS
99mTc-(2-Me) IOR CEA presented favorable in vitro and in vivo properties. Therefore this label was compared to 99mTc-monoclonal antibody BW 431/26. Similar characteristics were found. Clinical studies also revealed identical biodistribution profile.
Gano
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Instituto Tecnológico Nuclear, Sacavém, Portugal.
Fernandes
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Cantinho
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Santos
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Pena
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Vieira
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Salgado
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Patrício
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D000818:Animals; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics; D002272:Carcinoembryonic Antigen / Q000276:immunology*; D004355:Drug Stability; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D007202:Indicators and Reagents; D007553:Isotope Labeling / Q000379:methods; D008623:Mercaptoethanol; D051379:Mice; D016719:Radioimmunodetection; D019275:Radiopharmaceuticals / Q000138:chemical synthesis* / Q000493:pharmacokinetics*; D012044:Regression Analysis; D013667:Technetium / Q000493:pharmacokinetics; D014018:Tissue Distribution
D000911:Antibodies, Monoclonal; D002272:Carcinoembryonic Antigen; D007202:Indicators and Reagents; D019275:Radiopharmaceuticals; D008623:Mercaptoethanol; D013667:Technetium