title: Heterodimeric bispecific antibody-derivatives against CD19 and CD16 induce effective antibody-dependent cellular cytotoxicity against B-lymphoid tumor cells.
abstract: Bispecific scFv antibody-derivatives (bsscFvs) recruiting natural killer (NK) cells for the lysis of malignant cells have therapeutic potential. However, a bsscFv specific for the B-lymphoid tumor antigen CD19 and the trigger molecule CD16 on NK cells had similar affinities for both antigens (42 and 58nM, respectively) and was not optimal for cytotoxicity. Therefore, a bispecific tribody (bsTb) was constructed with two binding sites for CD19 and one for CD16. This bsTb contained a CD19-specific Fab fragment carrying a CD16-specific scFv fused to its light chain and a CD19-specific scFv fused to its heavy chain. The bsTb was compared with a bispecific bibody (bsBb) lacking the CD19-specific scFv. The bsTb had 3-fold greater avidity for CD19 than the bsBb (8 and 24nM, respectively), while both had equal affinity for CD16 (56nM). Both molecules mediated antibody-dependent cellular cytotoxicity (ADCC) of leukemia-derived SEM cells and primary cells from leukemia patients. The bsTb showed half-maximum effective concentrations (EC(50)) of 55pM and promoted equal lysis as the bsBb and the bsscFv at 6- and 12-fold lower concentrations, respectively. Among these three molecules the bsTb showed the most promising in vitro properties which are anticipated to be displayed also in vivo.
authors.affiliation: Chair of Genetics, University of Erlangen-Nuremberg, Erwin-Rommel-Straße 3, 91058 Erlangen, Germany. c.kellner@med2.uni-kiel.de
authors.forename: Christian
authors.initials: C
authors.lastname: Kellner
authors.forename: Joerg
authors.initials: J
authors.lastname: Bruenke
authors.forename: Heike
authors.initials: H
authors.lastname: Horner
authors.forename: Joerg
authors.initials: J
authors.lastname: Schubert
authors.forename: Michael
authors.initials: M
authors.lastname: Schwenkert
authors.forename: Kristin
authors.initials: K
authors.lastname: Mentz
authors.forename: Karin
authors.initials: K
authors.lastname: Barbin
authors.forename: Christoph
authors.initials: C
authors.lastname: Stein
authors.forename: Matthias
authors.initials: M
authors.lastname: Peipp
authors.forename: Bernhard
authors.initials: B
authors.lastname: Stockmeyer
authors.forename: Georg H
authors.initials: GH
authors.lastname: Fey
mesh_terms: D018033:Antibodies, Bispecific / Q000737:chemistry*; D000920:Antibody-Dependent Cell Cytotoxicity / Q000276:immunology; D018941:Antigens, CD19 / Q000737:chemistry*; D045744:Cell Line, Tumor; D019281:Dimerization; D005434:Flow Cytometry / Q000379:methods; D006801:Humans; D007128:Immunoglobulin Fragments; D007167:Immunotherapy / Q000379:methods; D007700:Kinetics; D007963:Leukocytes, Mononuclear / Q000166:cytology; D016393:Lymphoma, B-Cell / Q000276:immunology* / Q000628:therapy; D011485:Protein Binding; D017452:Receptors, IgG / Q000737:chemistry*; D011993:Recombinant Fusion Proteins / Q000737:chemistry
chemical_list: D018033:Antibodies, Bispecific; D018941:Antigens, CD19; D007128:Immunoglobulin Fragments; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins