Pharmacokinetics, Dosimetry and Toxicity of Rhenium-188-Labeled Anti-Carcinoembryonic Antigen Monoclonal Antibody, MN-14, in Gastrointestinal Cancer

antibody (MAb), were assessed in patients in advanced gastrointes tinal cancer. In addition, the dose-limiting toxicity (DLT) and maxi mum tolerated dose of fractionated doses of this agent were determined. Methods: Eleven patients were administered radioac tive doses of directly labeled 188Re-MN-14 IgG, ranging from 20.5 mCi to 161.0 mCi (2.0 mg-4.9 mg). Ten of these patients received two or three MAb infusions, given 3-4 days apart, delivering total doses of 30 mCi/m2-80 mCi/m2. External scintigraphy was used to evaluate the MAb biodistribution, and quantitative external scinti-graphic methods were used to determine the organ and tumor radiation doses. Results: The biodistribution studies showed en hanced 188Re-MN-14 uptake in the liver, spleen and kidneys, compared to that of 131I-MN-14. The biological T1/2 values for 188Re-MN-14 in the blood and whole body (in hours) were 8.2 ±4.1 (n = 7) and 107.8 ±104.2 (n = 9), respectively (mean ±s.d.). The radiation absorbed doses (cGy/mCi) delivered to the total body, red marrow, lungs, liver, spleen and kidneys were 0.5 ±0.05,3.6 ±1.6