Effect of dose escalation of a monoclonal anti-CEA IgG on tumour localisation and tissue distribution in nude mice xenografted with human colon carcinoma

A monoclonal anti-CEA antibody (1H12) has been examined for the effect of dosage on tumour localisation in immunodeprived mice xenografted with human colon carcinoma. Increased doses produced a linear rise in the absolute concentration found in the tumour but this was found to depend on tumour size, with the smaller tumours (mean weight 44 mg) accumulating significantly more antibody compared to larger tumours (mean weight 146 mg). With the smallest tumour (18 mg), in which saturation was achieved, a 500 μg dose produced a concentration in tumour of 60 μg/g. In the larger tumours a dose of 256 μg produced a mean concentration of 5.2 μg/g. Prolonged retention of 1H12 by tumour up to 8 days, observed at doses of 4, 128 and 256 μg, indicated that the dynamics of localisation is unaffected by dosage.