Biodistribution of a radiolabelled monoclonal antibody NY3D11 recognizing the neural cell adhesion molecule in tumour xenografts and patients with small-cell lung cancer.

The neural cell adhesion molecule (NCAM) is highly expressed on the surface of small-cell-lung cancer (SCLC) cells. We have produced a monoclonal antibody, NY3D11, that binds to NCAM to investigate whether this antigen could be used to develop antibody-directed therapy for SCLC. 125I-labelled IgG and F(ab')2 fragments of NY3D11 localized selectively in human SCLC xenografts grown in nude mice. The human biodistribution of 131I-labelled NY3D11 after intravenous administration was investigated by gamma-camera imaging in six patients with SCLC. Three patients received IgG and three received F(ab')2. No evidence of localization to primary tumours or metastases was seen and antibody accumulated rapidly in the liver and bone marrow. The probable explanation for this distribution is that NY3D11 reacted with soluble NCAM or natural killer cells that possess the CD56 (NCAM) antigen.