[Organ distribution of 99m technetium-labeled OK-432 following intravenous administration in man]

We investigated the pharmacokinetics of OK-432, au immunomodulator of streptococcus preparation which, is used in cancer patients for active nonspecific immunotherapy. First, OK-432 was labeled with 99mTechnetium in vitro. Four patients with malignancy were studied. By the method of scintigraphy using gamma camera, OK-432 administered intravenously was found to be distributed in the liver, lung and spleen, by the decreasing grade. When OK-432 was administered subcutaneously or intramuscularly in the buttocks, most of the radioactivity of 99mTechnetium remained locally at the injected site. These results suggested that OK-432 given intravenously was effectively phagocytized by cells of reticuloendothelial system (RES). Compared with other routes of administration, the intravenous route of OK-432 administration is thus considered more effective in order to stimulate RES, which is responsible for the first step of immune reaction.