Selective localization of a radioiodinated phospholipid ether analog in human tumor xenografts

Administration of [125I]-rac-1-O-[12-(m-iodophenyl)dodecyl-2-O-methylglycero-3- phosphocholine (NM-294) to athymic mice implanted with human tumors of several histologies, including adenocarcinoma of the ovary and colon, melanoma and small-cell carcinoma of the lung, resulted in excellent images of the tumors by gamma camera scintigraphy. Images of the tumor were obtained at 5 days or more postinjection, by which time nearly all background activity had cleared from the liver and gastrointestinal tract. Tumor-to-blood ratios at this time were quite high and ranged from approximately 8:1 (melanoma) to 30:1 (ovarian carcinoma), which is consistent with the scintigraphic images obtained in all human tumor models. Lipid extraction of the liver and tumor at 13 days postinjection showed that most of the radioactivity in these tissues remained associated with the parent compound, with only a small amount retained by the liver. Appropriately radioiodinated NM-294 has substantial potential as a tumor-avid radiopharmaceutical.