title: Effective elimination of acute myeloid leukemic cells by recombinant bispecific antibody derivatives directed against CD33 and CD16.
abstract: Single-chain Fv triplebodies (sctb), consisting of a single polypeptide chain with 3 single-chain antibody variable fragments connected in tandem, were generated as antileukemic agents. A CD19-specific sctb of this format has previously been shown to be superior to a bispecific single-chain Fv antibody fragment (bsscFv) for the elimination of leukemic B-lineage cells, but corresponding targeted agents for the treatment of acute myeloid leukemia are still lacking. For this purpose, both a bsscFv and a sctb specific for CD33 and the trigger molecule CD16 (FcgammaRIII) were produced. The sctb displayed 3.5-fold greater avidity for CD33 than the bsscFv 33xds16, whereas both had close to equal affinity for CD16. In antibody-dependent cellular cytotoxicity (ADCC) reactions with human mononuclear cells as effectors, both the bsscFv 33xds16 and the sctb induced lysis of tumor cells with half maximum effective concentrations (EC50) in the low picomolar range. It is interesting to note that the sctb promoted equal lysis of human leukemia-derived cell lines at 10 to 200-fold lower concentrations than the bsscFv. Both molecules mediated ADCC of primary patient cells. In conclusion, both the bsscFv 33xds16 and the sctb 33xds16x33 eliminated acute myeloid leukemia cells in ADCC reactions, but the novel sctb format showed significantly greater specific activity.
authors.affiliation: Computer-Chemie-Centrum, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Singer
authors.forename: Christian
authors.initials: C
authors.lastname: Kellner
authors.forename: Harald
authors.initials: H
authors.lastname: Lanig
authors.forename: Michael
authors.initials: M
authors.lastname: Aigner
authors.forename: Bernhard
authors.initials: B
authors.lastname: Stockmeyer
authors.forename: Fuat
authors.initials: F
authors.lastname: Oduncu
authors.forename: Michael
authors.initials: M
authors.lastname: Schwemmlein
authors.forename: Christoph
authors.initials: C
authors.lastname: Stein
authors.forename: Kristin
authors.initials: K
authors.lastname: Mentz
authors.forename: Andreas
authors.initials: A
authors.lastname: Mackensen
authors.forename: Georg H
authors.initials: GH
authors.lastname: Fey
mesh_terms: D000818:Animals; D018033:Antibodies, Bispecific / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D000915:Antibody Affinity; D000920:Antibody-Dependent Cell Cytotoxicity / Q000187:drug effects / Q000276:immunology; D015703:Antigens, CD / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D015214:Antigens, Differentiation, Myelomonocytic / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D016466:CHO Cells; D003198:Computer Simulation; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D007167:Immunotherapy; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy / Q000276:immunology* / Q000473:pathology; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D015202:Protein Engineering; D055550:Protein Stability; D017452:Receptors, IgG / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D063268:Sialic Acid Binding Ig-like Lectin 3
chemical_list: D018033:Antibodies, Bispecific; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; C571163:CD33 protein, human; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins; D063268:Sialic Acid Binding Ig-like Lectin 3