title: Characterization of CD33/CD3 Tetravalent Bispecific Tandem Diabodies (TandAbs) for the Treatment of Acute Myeloid Leukemia.
abstract: OBJECTIVE
  Randomized studies with gemtuzumab ozogamicin have validated CD33 as a target for antigen-specific immunotherapy of acute myelogenous leukemia (AML). Here, we investigated the potential of CD33/CD3-directed tandem diabodies (TandAbs) as novel treatment approach for AML. These tetravalent bispecific antibodies provide two binding sites for each antigen to maintain the avidity of a bivalent antibody and have a molecular weight exceeding the renal clearance threshold, thus offering a longer half-life compared to smaller antibody constructs.
  
  
  METHODS
  We constructed a series of TandAbs composed of anti-CD33 and anti-CD3 variable domains of diverse binding affinities and profiled their functional properties in CD33+human leukemia cell lines, xenograft models, and AML patient samples.
  
  
  RESULTS
  Our studies demonstrated that several CD33/CD3 TandAbs could induce potent, dose-dependent cytolysis of CD33+AML cell lines. This effect was modulated by the effector-to-target cell ratio and strictly required the presence of T cells. Activation and proliferation of T cells and maximal AML cell cytolysis correlated with high avidity to both CD33 and CD3. High-avidity TandAbs were broadly active in primary specimens from patients with newly diagnosed or relapsed/refractory AML in vitro, with cytotoxic properties independent of CD33 receptor density and cytogenetic risk. Tumor growth delay and inhibition were observed in both prophylactic and established HL-60 xenograft models in immunodeficient mice.
  
  
  CONCLUSIONS
  Our data show high efficacy of CD33/CD3 TandAbs in various preclinical models of human AML. Together, these findings support further study of CD33/CD3 TandAbs as novel immunotherapeutics for patients with AML. Clin Cancer Res; 22(23); 5829-38. ©2016 AACR.
authors.affiliation: Affimed GmbH, Biomunex Pharmaceuticals, Paris, France.
authors.forename: Uwe
authors.initials: U
authors.lastname: Reusch
authors.affiliation: Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors.forename: Kimberly H
authors.initials: KH
authors.lastname: Harrington
authors.affiliation: Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington.
authors.forename: Chelsea J
authors.initials: CJ
authors.lastname: Gudgeon
authors.affiliation: Affimed GmbH, Biomunex Pharmaceuticals, Paris, France.
authors.forename: Ivica
authors.initials: I
authors.lastname: Fucek
authors.affiliation: Affimed GmbH, Biomunex Pharmaceuticals, Paris, France.
authors.forename: Kristina
authors.initials: K
authors.lastname: Ellwanger
authors.affiliation: Affimed GmbH, Biomunex Pharmaceuticals, Paris, France.
authors.forename: Michael
authors.initials: M
authors.lastname: Weichel
authors.affiliation: Affimed GmbH, Biomunex Pharmaceuticals, Paris, France.
authors.forename: Stefan H J
authors.initials: SH
authors.lastname: Knackmuss
authors.affiliation: Affimed GmbH, Biomunex Pharmaceuticals, Paris, France.|Biomunex Pharmaceuticals, 96 bis Boulevard Raspail, 75006 Paris, France.
authors.forename: Eugene A
authors.initials: EA
authors.lastname: Zhukovsky
authors.affiliation: Amphivena Therapeutics, Inc., South San Francisco, California.
authors.forename: Judith A
authors.initials: JA
authors.lastname: Fox
authors.affiliation: Amphivena Therapeutics, Inc., South San Francisco, California.
authors.forename: Lori A
authors.initials: LA
authors.lastname: Kunkel
authors.affiliation: Amphivena Therapeutics, Inc., South San Francisco, California. jguenot@amphivena.com.
authors.forename: Jeanmarie
authors.initials: J
authors.lastname: Guenot
authors.affiliation: Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington.|Division of Hematology/Department of Medicine, University of Washington, Seattle, Washington.|Department of Epidemiology, University of Washington, Seattle, Washington.
authors.forename: Roland B
authors.initials: RB
authors.lastname: Walter
mesh_terms: D000617:Aminoglycosides / Q000276:immunology; D000818:Animals; D018033:Antibodies, Bispecific / Q000276:immunology*; D000911:Antibodies, Monoclonal / Q000276:immunology*; D061067:Antibodies, Monoclonal, Humanized / Q000276:immunology; D001665:Binding Sites / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology*; D045744:Cell Line, Tumor; D000079982:Gemtuzumab; D006207:Half-Life; D006801:Humans; D007167:Immunotherapy / Q000379:methods; D015470:Leukemia, Myeloid, Acute / Q000276:immunology* / Q000628:therapy*; D051379:Mice; D063268:Sialic Acid Binding Ig-like Lectin 3 / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D000617:Aminoglycosides; D018033:Antibodies, Bispecific; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D017252:CD3 Complex; C571163:CD33 protein, human; D063268:Sialic Acid Binding Ig-like Lectin 3; D000079982:Gemtuzumab