Development of technetium-99m and rhenium-186 labeled monoclonal antibodies for imaging and therapy.

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This study was performed to develop new imaging and therapeutic methods using technetium-99m and rhenium-186 labeled monoclonal antibodies.Technetium-99m labeled antibodies against carcinoembryonic antigen (CEA) were intravenously administered to patients with colorectal cancer, and its biodistribution and tumor uptake were examined in 12 patients. Eleven (92%) cases showed positive results with antibodies and tumor-to-normal tissue ratios obtained with SPECT correlated well with those obtained using surgical specimen. The highest tumor-to-normal tissue ratio reached more than 14 and there were several cases who seemed to be good candidates for radioimmunotherapy. Techetium-99m labeled anti-CA125 antibodies also accumulated in the ovarian cancer tissues in 3 out of 7 cases and needs further investigation.The biggest problem inherent to clinical use of monoclonal antibodies is the generation of human anti-murine antibody (HAMA) in the serum of patients who received monoclonal antibodies. Rapid progress of gene technology allowed us to produced humanized monoclonal antibodies. Technetium-99m labeled humanized antibodies were safely administered to patients and no HAMA were detectable in their serum. Clinical use of humanized antibodies seemed promising not only in the immunoscintigraphy but also in the therapy of cancer.