HEMOSTASIS, THROMBOSIS, AND VASCULAR BIOLOGY Selective targeted delivery of TNF to tumor blood vessels

We sought to enhance the selective toxicity of tumor necrosis factor (TNF ) to permit its systemic use in cancer therapy. Because ligand-targeted therapeutics have proven successful in improving the selective toxicity of drugs, we prepared a fusion protein (L19mTNF ) composed of mouse TNF and a high-affinity antibody fragment (L19 scFv) to the extradomain B (ED-B) domain of fibronectin, a marker of angiogenesis. L19mTNF was expressed in mammalian cells, purified, and characterized. L19mTNF was an immunoreactive and biologically active homotrimer. Radiolabeled L19mTNF selectively targeted tumor neovasculature in tumorbearing mice, where it accumulated selectively and persistently (tumor-to-blood ratio of the percentage of injected dose per gram [%ID/g] of 700, 48 hours from injection). L19mTNF showed a greater anticancer therapeutic activity than both mTNF and TN11mTNF , a control fusion protein in which an antibody fragment, irrelevant in the tumor model used, substituted for L19. This activity was further dramatically enhanced by its combination with melphalan or the recently reported fusion protein L19-IL2. In conclusion, L19mTNF allows concentrating therapeutically active doses of TNF at the tumor level, thus opening new possibilities for the systemic use of TNF in cancer therapy. (Blood. 2003;102:4384-4392)