Chimeric monoclonal antibody A7-Fab coupled to magnetic particles as a contrast agent of MR imaging

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The use of magnetic particles as contrast agents in MR imaging have been proposed. The total magnetic moment of ferromagnetic particles is approximately one order of magnitude larger than that found for paramagnetic materials of similar size. We coupled chimeric monoclonal antibody A7, which specifically reacts with human pancreatic carcinoma, to Lignosite FML (ferromagnetic particles) in order to improve the distinguishment between pancreatic carcinoma and other tissues. We examined the retaining in vitro immunoreactivity of ferromagnetic particles bound to ChA7Fab and their in vivo distribution in nude mice bearing human pancreatic carcinoma xenografts were examined. ChA7Fab-Lignosite FML retained binding activities nearly identical to ChA7Fab. Significantly more of the radiolabeled ChA7Fab-Lignosite FML accumulated in the tumor than did normal mouse IgGFab-Lignosite FML (P<0.05). ChA7Fab-Lignosite FML and ^<125>I labeled normal mouse IgGfab-Lignosite FML disappeared from blood rapidly. As for all resected normal tissues, the accumulation levels of ^<125>I labeled ChA7Fab-Lignosite FML were lower than those for the tumors and decreased linearly with time. From these experiments, we conclude that ChA7Fab coupled to Lignosite FML is suitable for contrast agent of MR imaging of human pancreatic carcinoma.