title: A CD19-specific single-chain immunotoxin mediates potent apoptosis of B-lineage leukemic cells.
abstract: CD19 is a B-lineage-specific transmembrane signaling protein participating in the control of proliferation and differentiation. It is present at high surface density on chronic B-lymphocytic leukemia (B-CLL) cells and cells of other B-cell malignancies, and is a prime target for therapy with antibody-derived agents. Many attempts have been made to target malignant cells via CD19, but to date none of these agents have received drug approval. Here we report the design of a monovalent immunotoxin consisting of a CD19-specific single-chain Fv antibody fragment fused to a derivative of Pseudomonas Exotoxin A. This fusion protein induced efficient antigen-restricted apoptosis of several human leukemia- and lymphoma-derived cell lines including Nalm-6, which it eliminated at an effective concentration (EC(50)) of 2.5 nM. The agent displayed synergistic toxicity when used in combination with valproic acid and cyclosporin A in cell-culture assays. It induced apoptosis of primary malignant cells in 12/12 samples from B-CLL patients, including patients responding poorly to fludarabine, and of cells from one pediatric acute lymphoblastic leukemia patient. In NOD/SCID mice transplanted with Nalm-6 cells, the toxin prevented engraftment and significantly prolonged survival of treated mice. Owing to its efficient antigen-restricted antileukemic activity, the agent deserves further development towards clinical testing.
authors.affiliation: Genetics, University of Erlangen-Nuremberg, Erwin-Rommel-Strasse 3, Erlangen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Schwemmlein
authors.forename: J
authors.initials: J
authors.lastname: Stieglmaier
authors.forename: C
authors.initials: C
authors.lastname: Kellner
authors.forename: M
authors.initials: M
authors.lastname: Peipp
authors.forename: D
authors.initials: D
authors.lastname: Saul
authors.forename: F
authors.initials: F
authors.lastname: Oduncu
authors.forename: B
authors.initials: B
authors.lastname: Emmerich
authors.forename: B
authors.initials: B
authors.lastname: Stockmeyer
authors.forename: P
authors.initials: P
authors.lastname: Lang
authors.forename: J D
authors.initials: JD
authors.lastname: Beck
authors.forename: G H
authors.initials: GH
authors.lastname: Fey
mesh_terms: D000818:Animals; D018941:Antigens, CD19 / Q000187:drug effects* / Q000276:immunology; D017209:Apoptosis / Q000187:drug effects*; D004353:Drug Evaluation, Preclinical; D004357:Drug Synergism; D005098:Exotoxins; D006801:Humans; D007128:Immunoglobulin Fragments; D000922:Immunotoxins / Q000494:pharmacology* / Q000627:therapeutic use; D015448:Leukemia, B-Cell / Q000188:drug therapy* / Q000473:pathology; D051379:Mice; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000188:drug therapy; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy* / Q000473:pathology; D011549:Pseudomonas; D011993:Recombinant Fusion Proteins / Q000494:pharmacology / Q000627:therapeutic use; D015996:Survival Rate; D047368:Tumor Burden / Q000187:drug effects; D014407:Tumor Cells, Cultured
chemical_list: D018941:Antigens, CD19; D005098:Exotoxins; D007128:Immunoglobulin Fragments; D000922:Immunotoxins; D011993:Recombinant Fusion Proteins