huBC1-IL12, an immunocytokine which targets EDB-containing oncofetal fibronectin in tumors and tumor vasculature, shows potent anti-tumor activity in human tumor models.
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.
Lo
Kin-Ming
KM
EMD Lexigen Research Center, 45A Middlesex Turnpike, Billerica, MA 01821, USA. klo@emdlexigen.com
Lan
Yan
Y
Lauder
Scott
S
Zhang
Jinyang
J
Brunkhorst
Beatrice
B
Qin
Guozhong
G
Verma
Rakesh
R
Courtenay-Luck
Nigel
N
Gillies
Stephen D
SD
D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005353:Fibronectins / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G; D007143:Immunoglobulin Heavy Chains; D007150:Immunohistochemistry; D018664:Interleukin-12 / Q000276:immunology / Q000493:pharmacokinetics / Q000627:therapeutic use*; D008297:Male; D051379:Mice; D009374:Neoplasms, Experimental / Q000276:immunology / Q000628:therapy*; D020033:Protein Isoforms / Q000276:immunology / Q000493:pharmacokinetics / Q000627:therapeutic use; D011993:Recombinant Fusion Proteins / Q000138:chemical synthesis* / Q000276:immunology / Q000627:therapeutic use*
C067625:FN1 protein, human; D005353:Fibronectins; D007074:Immunoglobulin G; D007143:Immunoglobulin Heavy Chains; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D018664:Interleukin-12