title: Preclinical studies comparing different bispecific antibodies for redirecting T cell cytotoxicity to extracellular antigens on prostate carcinomas.
abstract: BACKGROUND
  Bispecific antibodies (BiAbs) are used to enhance targeting of T cells and other cytotoxic agents to tumors while minimizing non-specific tissue toxicities. This study compares the targeting efficacy of 3 BiAbs derived from chemically heteroconjugating a T cell-directed monoclonal antibody (mAb) to 9184, 9187 or 9189, which are mAbs directed at extracellular antigens expressed on human prostate carcinoma cell lines.
  
  
  METHODS
  9184 (anti-Her2/neu), 9187 (anti-gp55) and 9189 (anti-gp42) were each heteroconjugated to anti-CD3 to produce BiAbs capable of binding to ("arming") anti-CD3 activated T cells (ATC) and redirecting their cytotoxicity to prostate cancer cells expressing the respective antigen. ATC from cancer patients and/or normal subjects were armed with each BiAb and tested in co-cultures with PC-3, DU 145, and LNCaP cells for binding, cytotoxicity, and cytokine secretion.
  
  
  RESULTS
  All 3 tumor-directed mAbs bound to each of the prostate cancer cell lines. ATC armed with 9184Bi statistically augmented cytotoxicity directed at PC-3 and increased IFN-gamma, TNF-alpha, and GM-CSF secretion as well as induced IFN-gamma EliSpots above that seen for 9187Bi, 9189Bi, ATC alone or ATC armed with an irrelevant BiAb. 9184Bi-armed ATC mediated significant cytotoxicity against LNCaP and DU 145 cells as well. When we armed ATC from 6 cancer patients with 9184Bi, 9184Bi markedly enhanced cytotoxicity of ATC from 5 of the 6 patients.
  
  
  CONCLUSIONS
  Arming ATC with BiAbs augments cytotoxicity directed at prostate cancer lines expressing the target antigens. Arming with 9184Bi was the most effective at redirecting cytotoxicity at PC-3 cells and inducing cytokine secretion. As an alternative to mAb therapy with anti-HER2, the HER2 antigen may provide a suitable target for redirecting anti-cancer immune cells, immunobiologicals, or other agents to HRPC.
authors.affiliation: Clinical Sciences Center, University of Wisconsin Medical School, Madison, WI 53792, USA.
authors.forename: Hillary E
authors.initials: HE
authors.lastname: Lum
authors.forename: Mendy
authors.initials: M
authors.lastname: Miller
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Davol
authors.forename: Ryan C
authors.initials: RC
authors.lastname: Grabert
authors.forename: James B
authors.initials: JB
authors.lastname: Davis
authors.forename: Lawrence G
authors.initials: LG
authors.lastname: Lum
mesh_terms: D018033:Antibodies, Bispecific / Q000276:immunology / Q000494:pharmacology*; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D017252:CD3 Complex / Q000276:immunology; D045744:Cell Line, Tumor; D016207:Cytokines / Q000276:immunology / Q000378:metabolism; D003602:Cytotoxicity, Immunologic / Q000187:drug effects / Q000276:immunology; D006801:Humans; D007116:Immunization, Passive / Q000379:methods*; D018796:Immunoconjugates / Q000276:immunology / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects / Q000276:immunology; D008297:Male; D011471:Prostatic Neoplasms / Q000276:immunology* / Q000378:metabolism / Q000628:therapy*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism
chemical_list: D018033:Antibodies, Bispecific; D000911:Antibodies, Monoclonal; D017252:CD3 Complex; D016207:Cytokines; D018796:Immunoconjugates; D018719:Erb-b2 Receptor Tyrosine Kinases