Human IgM Monoclonal Antibody 16.88: Pharmacokinetics and Immunogenicity in Colorectal Cancer Patients

Twenty colorectal cancer patients were given an intravenous injection of human IgM monoclonal antibody (MAb) 16.88 (8 mg) conjugated to 131I for tumor localization. After a 2-week interval, a second injection with 200, 500, or 1000 mg of unlabeled antibody added was given to groups of five patients each. At the end of the 2-hour infusion, 66 % of the radioactivity remained in the circulation. Blood clearance of the mI-labeled MAb 16.88 was biphasic with a mean half-life (T^a) of 12 hours and Tv $ of 45 hours. Clearance rate was 0.09 L/hour. More than 90 % of the 131I in serum was protein bound, with an immunoreactive fraction of 80 % in the first 48 hours. Size exclusion chromatography indicated no degradation products other than 13II in serum and urine. The urinary excretion rate of 13II increased to 1.5 % of the dose per hour at 24 hours, with 50 % of the dose excreted i