huBC1-IL12, an immunocytokine which targets EDB-containing oncofetal fibronectin in tumors and tumor vasculature, shows potent anti-tumor activity in human tumor models

Cancer Immunol Immunother. 2007 Apr;56(4):447-57. doi: 10.1007/s00262-006-0203-1. Epub 2006 Jul 28.


IL-12 is a cytokine which showed anti-tumor effects in clinical trials, but also produced serious toxicity. We describe a fusion protein, huBC1-IL12, designed to achieve an improved therapeutic index by specifically targeting IL-12 to tumor and tumor vasculature. huBC-1 is a humanized antibody that targets a cryptic sequence of the human ED-B-containing fibronectin isoform, B-FN, present in the subendothelial extracellular matrix of most aggressive tumors. B-FN is oncofetal and angiogenesis-associated, and is undetectable in most normal adult tissues. The original murine BC-1 antibody has been used successfully for immunoscintigraphy to image brain tumor mass in glioblastoma patients. In huBC1-IL12, each of the IgG heavy chains is genetically fused to the N-terminus of the IL-12 p35 subunit, which in turn is disulfide-bonded to the p40 subunit, resulting in a hexameric molecule of MW of approximately 300 kDa. Since human IL-12 has no biological activity in mice, we produced huBC1-muIL12 as a surrogate molecule for animal tumor models. Despite the relatively poor PK profile of this molecule in mice and the apparent drawbacks of xenogeneic models in SCID mice, which lack T and B cells, one cycle of treatment with huBC1-muIL12 was efficacious in the PC3mm2, A431, and HT29 subcutaneous tumor models and PC3mm2 lung metastasis model. This molecule also was found to have surprisingly low toxicity in immunocompetent mice. A fusion protein that contains human IL-12 (huBC1-huIL12), which is a suitable molecule for investigation as a therapeutic, has also been produced. This protein has been shown to have a longer serum half-life than huBC1-muIL12 in mice, and retains both antigen binding and IL-12 activity in in vitro assays.

MeSH terms

  • Animals
  • Electrophoresis, Polyacrylamide Gel
  • Female
  • Fibronectins / immunology*
  • Humans
  • Immunoglobulin G
  • Immunoglobulin Heavy Chains
  • Immunohistochemistry
  • Interleukin-12 / immunology
  • Interleukin-12 / pharmacokinetics
  • Interleukin-12 / therapeutic use*
  • Male
  • Mice
  • Neoplasms, Experimental / immunology
  • Neoplasms, Experimental / therapy*
  • Protein Isoforms / immunology
  • Protein Isoforms / pharmacokinetics
  • Protein Isoforms / therapeutic use
  • Recombinant Fusion Proteins / chemical synthesis*
  • Recombinant Fusion Proteins / immunology
  • Recombinant Fusion Proteins / therapeutic use*


  • FN1 protein, human
  • Fibronectins
  • Immunoglobulin G
  • Immunoglobulin Heavy Chains
  • Protein Isoforms
  • Recombinant Fusion Proteins
  • Interleukin-12