188 Re - AntiCEA Mab. Preparation and biological evaluation

Monoclonal antibodies are the most recent candidate molecules for the radiopharmaceutical preparation used in radioimmunotherapy and radiodiagnostic, function of the used radionuclide. Our study presents results in: - 188 Re direct labelling of Monoclonal Anti-Human Carcinoembrionic antigen clone C6G9 (anti-CEA Mab); - biological evaluation of 188 Re-antiCEA Mab on tumour bearing animals. The steps in labelling process are: - pre-reduction of -S-S- bridges of antiCEA-Mab molecule with ascorbic acid in pH = 5; - preparation of the reducing system for 186 ReO4- in presence of Sn2+ ion excess; - coupling 186 Re (red) to -SH groups of the biomolecule. The specific reactions of each of the above steps are controlled by: incubation time and temperature, pH, molar ratio 186 Re to antiCEA-Mab. The incubation at 37 deg. C temperature, 20 hour time and pH = 5 for samples of 188 Re to antiCEA with molar ratio 1.6:1 leads to a 85-90% labelling yield.188 Re-antiCEA purified samples by gel elution chromatography method were i.p. injected on tumour bearing animals. The sample radioactivity was 1.2 mCi/0.2 ml. The biodistribution registered at 4, 24 and 48 hours post injection presents a maximum accumulation in tumour at 24 h after injection. Λtumour/Λblood = 6.2:1 was the activity ratio after 24 h post injection. (authors)