title: A novel high-affinity human monoclonal antibody to mesothelin.
abstract: Mesothelin is a glycosylphosphatidylinositol-anchored glycoprotein that is highly expressed on the cell surface of mesothelioma, ovarian cancer and other malignant tumors. The interaction between mesothelin and CA125 (also called MUC16) may facilitate the implantation and metastasis of tumors in the peritoneal cavity. A desirable therapeutic agent involves finding a fully human monoclonal antibody (mAb) that binds to mesothelin or CA125 and inhibits their interaction. Here, we report the identification of a novel human mAb to mesothelin. HN1, a human single-chain Fv specific for mesothelin, was isolated from a naïve human single-chain variable fragment (scFv) phage display library. To investigate HN1 as a potential therapeutic, we generated a fully human IgG with the γ 1 heavy chain and the κ light chain and an immuntoxin by fusing the HN1 scFv to a truncated Pseudomonas exotoxin A. The HN1 IgG kills cancer cells with very strong antibody-dependent cell-mediated cytotoxicity. HN1 binds a conformation-sensitive epitope in human mesothelin with high affinity (K(D) = 3 nM). The HN1 epitope is different from that of SS1, a mouse Fv used to develop therapeutic antibodies that are currently in clinical trials. HN1 binds to cell surface-associated mesothelin on human mesothelioma, ovarian cancer, lung adenocarcinoma and pancreatic cancer cells. In addition, HN1 can functionally block the interaction of mesothelin and CA125 on cancer cells. Most importantly, because the HN1 immuntoxin kills mesothelin-expressing cancer cells with high cytotoxic activity, we believe that it has significant potential for mesothelin-expressing cancer treatment and diagnosis.
authors.affiliation: Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4264, USA. homi@mail.nih.gov
authors.forename: Mitchell
authors.initials: M
authors.lastname: Ho
authors.forename: Mingqian
authors.initials: M
authors.lastname: Feng
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Fisher
authors.forename: Christoph
authors.initials: C
authors.lastname: Rader
authors.forename: Ira
authors.initials: I
authors.lastname: Pastan
mesh_terms: D036002:ADP Ribose Transferases; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000915:Antibody Affinity; D000920:Antibody-Dependent Cell Cytotoxicity / Q000276:immunology; D001427:Bacterial Toxins; D045744:Cell Line, Tumor; D002469:Cell Separation; D004797:Enzyme-Linked Immunosorbent Assay; D005098:Exotoxins; D005434:Flow Cytometry; D058851:GPI-Linked Proteins / Q000276:immunology; D006801:Humans; D007167:Immunotherapy / Q000379:methods*; D008562:Membrane Glycoproteins / Q000276:immunology*; D000090204:Mesothelin; D019151:Peptide Library; D016133:Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins / Q000138:chemical synthesis* / Q000276:immunology*; D057127:Single-Chain Antibodies / Q000276:immunology; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D000911:Antibodies, Monoclonal; D001427:Bacterial Toxins; D005098:Exotoxins; D058851:GPI-Linked Proteins; D008562:Membrane Glycoproteins; D000090204:Mesothelin; D019151:Peptide Library; D011993:Recombinant Fusion Proteins; D057127:Single-Chain Antibodies; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A; C000715528:Msln protein, mouse