Immunoscintigraphy and Pharmacokinetics of Indium‐111‐labeled ZME‐018 Monoclonal Antibody in Patients with Malignant Melanoma

Immunoscintigraphic and pharmacokinetic characteristics of 111In‐labeled ZME‐018 monoclonal antibody were examined in 8 patients with malignant melanoma. Each patient received a single intravenous infusion of 20 mg of ZME‐018, coupled to 3 mCi of 111In without any acute toxicity. Scintigrams were taken 1, 3, and 6 days after the administration, and blood and urine samples were also taken frequently. Rapid clearance of some radioactivity was seen in early urine samples in the form of 111In DTPA, but after 1 day, urinary excretion of radioactivity was slow and steady, with an average of 2.5% of the injected dose excreted per day. The scans demonstrated that there was blood retention of radioactivity in the heart and great vessels 1 day after infusion and considerable clearance from the blood pool occurred by 3 days. However, 111In was deposited in the liver, spleen and bone for up to 6 days. The optimal time for imaging appeared to be at 3 days. Nineteen out of 26 known lesions or 6 out of 8 patients were positive. There were 21 lesions detected that were not suspected during the work‐up the patient. Five patients developed human anti‐mouse antibody in the serum by 3 weeks. These results suggest that immunoscintigraphy with 111In‐labeled ZME‐018 antibody is safe and useful for the detection of metastatic lesions in a selected group of patients with malignant melanoma.