Effect of antibody dose on the imaging and biodistribution of indium-111 9.2.27 anti-melanoma monoclonal antibody.

Eleven patients with metastatic melanoma underwent serial gamma camera imaging and biodistribution measurements after i.v. injection of escalating doses of [111In]9.2.27, an antimelanoma murine monoclonal antibody. Patients received a fixed dose of 1 mg of [111In]9.2.27, with no additional 9.2.27 (five patients), or co-infused with 49 mg (five patients) or 99 mg (one patient) of unlabeled, unconjugated 9.2.27. Higher doses resulted in prolonged blood-pool retention, less uptake in spleen and bone marrow, and appeared to have a positive effect in improving tumor imaging. A dose of 1 mg of 9.2.27 permitted detection of tumors in two of five patients and two of ten lesions, while with greater than or equal to 50 mg, tumors were detected in all patients and in 24 of 32 lesions. Human gamma globulin injected prior to administration of [111In]9.2.27 failed to block the prominent liver, spleen, and bone marrow uptake. No toxicity was observed. These results indicate the feasibility of imaging metastatic melanoma with [111In]9.2.27 and suggest that antibody dose may be a critical determinant of biodistribution and tumor uptake.