Selective targeting of tumoral vasculature: comparison of different formats of an antibody (L19) to the ED-B domain of fibronectin.
We recently demonstrated that a human recombinant scFv, L19, reacting with the ED-B domain of fibronectin, a marker of angiogenesis, selectively targets tumoral vasculature in vivo. Using the variable regions of L19, we constructed and expressed a human "small immunoprotein" (SIP) and a complete human IgG1 and performed biodistribution studies in tumor-bearing mice to compare the blood clearance rate, in vivo stability and performance in tumor targeting of the 3 L19 formats [dimeric scFv (scFv)(2), SIP and IgG1]. The accumulation of the different antibody formats in the tumors studied was a consequence of the clearance rate and in vivo stability of the molecules. Using the SIP, the %ID/g in tumors was 2-5 times higher than that of the (scFv)(2), reaching a maximum 4-6 hr after injection. By contrast, the accumulation of IgG1 in tumors constantly rose during the experiments. However, due to its slow clearance, the tumor-blood ratio of the %ID/g after 144 hr was only about 3 compared to a ratio of 10 for the (scFv)(2) and 70 for the SIP after the same period of time. The different in vivo behavior of these 3 completely human L19 formats could be exploited for different diagnostic and/or therapeutic purposes, depending on clinical needs and disease. Furthermore, the fact that ED-B is 100% homologous in human and mouse, which ensures that L19 reacts equally well with the human and the murine antigen, should expedite the transfer of these reagents to clinical trials.
D000818:Animals; D000917:Antibody Formation; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005353:Fibronectins / Q000276:immunology*; D007124:Immunoenzyme Techniques; D007128:Immunoglobulin Fragments; D007457:Iodine Radioisotopes; D008546:Melanoma, Experimental / Q000098:blood supply* / Q000000981:diagnostic imaging*; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009389:Neovascularization, Pathologic / Q000000981:diagnostic imaging*; D010957:Plasmids; D020033:Protein Isoforms / Q000276:immunology; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D018243:Teratocarcinoma / Q000098:blood supply* / Q000000981:diagnostic imaging; D014018:Tissue Distribution
D005353:Fibronectins; D007128:Immunoglobulin Fragments; D007457:Iodine Radioisotopes; D020033:Protein Isoforms; D019275:Radiopharmaceuticals