ALBERT

Description: We sought to enhance the selective toxicity of tumor necrosis factor α (TNFα) 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 (L19mTNFα) composed of mouse TNFα and a high-affinity antibody fragment (L19 scFv) to the extradomain B (ED-B) domain of fibronectin, a marker of angiogenesis. L19mTNFα was expressed in mammalian cells, purified, and characterized. L19mTNFα was an immunoreactive and biologically active homotrimer. Radiolabeled L19mTNFα selectively targeted tumor neovasculature in tumor-bearing 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). L19mTNFα showed a greater anticancer therapeutic activity than both mTNFα and TN11mTNFα, 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, L19mTNFα allows concentrating therapeutically active doses of TNFα at the tumor level, thus opening new possibilities for the systemic use of TNFα in cancer therapy. (Blood. 2003;102:4384-4392)

Description: Angiogenic processes depend on the precise coordination of different cell types and a complex exchange of signals, many of which derive from new specific components of the provisional, angiogenesis-related, extracellular matrix (ECM). Angiogenesis-associated ECM components thus represent appealing targets for the selective delivery of therapeutic molecules to newly forming tumor vessels. Results of a previous study indicated that a high affinity recombinant antibody (L19) to ED-B, a domain contained in the angiogenesis-associated isoform of fibronectin (B-FN), selectively and efficiently targets tumor vessels. The present study shows that a fusion protein between L19 and interleukin 2 (L19–IL-2) mediates the selective delivery and concentration of IL-2 to tumor vasculature, thereby leading to a dramatic enhancement of the therapeutic properties of the cytokine. By contrast, IL-2 fused to an irrelevant recombinant antibody used as a control fusion protein showed neither accumulation in tumors nor therapeutic efficacy. Tumors in mice treated with L19–IL-2 were significantly smaller compared to those in animals treated with saline, the control fusion protein, or IL-2 alone (P = .003, .003, and .002, respectively). Moreover, no significant differences in size were observed among the tumors from the different control groups (using the control fusion protein, a mixture of IL-2 and L19, or saline alone). Immunohistochemical analysis of tumor infiltrates demonstrated a significantly higher number of T lymphocytes, natural killer cells, and macrophages, as well as increased interferon-γ (IFN-γ) accumulation, in tumors from animals treated with L19–IL-2 compared to tumors from control groups. The fact that ED-B is 100% homologous in human and mouse, thus ensuring that L19 reacts equally well with human and murine antigen, should ultimately expedite transfer of this reagent to clinical trials.