Oncofetal fibronectin (Extra Domain B) (onfFN (ED-B))

Oncofetal fibronectin, specifically the Extra Domain B (ED-B) variant, is a splice isoform of fibronectin that is virtually absent in normal adult tissues but highly expressed during embryogenesis and in the stroma of aggressive tumors, including melanoma. This variant is generated through alternative splicing of the fibronectin pre-mRNA and is closely associated with tumor angiogenesis and the epithelial-to-mesenchymal transition (EMT) required for metastasis. In melanoma, ED-B fibronectin serves as a specific marker for the tumor neovasculature and the invasive front of the tumor, facilitating cell migration and survival. Because of its high tumor-specificity and accessibility within the extracellular matrix, it has become a primary target for antibody-based delivery of therapeutic agents. Drugs like L19-IL2 and L19-TNF utilize high-affinity antibodies to concentrate potent cytokines directly at the tumor site, enhancing the anti-tumor immune response while minimizing systemic toxicity.

Other names

ED-B fibronectinB-fibronectinOncofetal fibronectinExtra Domain B-containing fibronectinEDB-FNEIIIB-containing fibronectin

Targeted delivery of immunomodulatory cytokines (e.g., IL-2, TNF) or pro-coagulant factors to the tumor microenvironment by binding to the ED-B domain of fibronectin, which is specifically expressed in neovascular structures and tumor stroma.