Immunoscintigraphy of prostatic cancer: Preliminary results with 111in‐labeled monoclonal antibody 7E11‐C5.3 (CYT‐356)

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Abstract
A phase 1 study was conducted with the investigational immunoscintigraphic agent, 111In‐CYT‐356, a radiolabeled, site‐specific immunoconjugate of monoclonal antibody 7E11‐C5.3, in 40 patients with prostatic carcioma and known distant metastases. Each patient received a single intravenous infusion of CYT‐356 (dose range, 0.1–5 mg) radiolabeled with approximately 5 mCi of 111In. None of the patients experienced adverse reactions. One patient who received a 5‐mg dose developed antibodies to the CYT‐356 immunoconjugate. 111In‐CYT‐356 immunoscintigraphy detected bony metastases in 21 of 38 patients (55%), including 12 of 14 (86%) receiving concomitant hormonal therapy, and soft tissue lesions in four of six patients (67%). Antibody imaging detected occult lesions in the bony pelvis and lumbar spine, which were confirmed by follow‐up imaging tests, in one patient. Higher CYT‐356 doses may clear the blood pool more slowly. These results suggest that 111In‐CYT‐356 can be safely administered to patients with prostatic carcinoma and that further clinical investigation of this agent is warranted.