new monoclonal antibody radiopharmaceutical for radioimmunoscintigraphy of breast cancer: direct labeling of antibody and its quality control

ABSTRACT

Radioimmunoscintigraphy [RIS] has found widespread clinical application in tumor diagnosis. The antibody [Ab] PR81 is a new murine anti-MUCl monoclonal antibody [MAb] against human breast carcinoma. In this study a very simple, rapid and efficient method for labeling of this MAb with [99m] Tc, particularly suitable for development of a [kit] is described. The reduction of Ab was performed with 2-mercaptoethanol [2-ME] at a molar ratio of 20001 [2-MEMAb] and the reduced Ab was labeled with [99m] Tc via methylene diphosphonate [MDP] as a transchelator. The labeling efficiency which was determined by instant thin layer chromatography [ITLC] was 94.2% +/- 2.3. Radiocolloides measured by cellulose nitrate electrophoresis were 2.5% +/- 1.7. In vitro stability of the labeled product in human serum which was measured by gel filtration chromatography [FPLC] was 70% +/- 5.7 over 24 hr. The integrity of labeled MAb was checked by means of SDS-PAGE and no significant fragmentation was observed. The results of the cell-binding studies showed that both labeled and unlabeled PR81 were able to compete for binding to MCF 7 cells. Biodistribution studies were performed in normal BALB/c mice at 4 and 24 hrs post-injection and no important accumulation was observed in vital organs. These results show that the new radiopharmaceutical may be considered as a promising candidate for imaging of breast cancer