title: Selective targeting and potent control of tumor growth using an EphA2/CD3-Bispecific single-chain antibody construct.
abstract: The EphA2 receptor tyrosine kinase is frequently overexpressed and functionally altered in malignant cells and thus provides opportunities for selective targeting of tumor cells. We describe here the development of a novel, bispecific single-chain antibody (bscAb) referred to as bscEphA2xCD3. This molecule simultaneously targets EphA2 on tumor cells and the T-cell receptor/CD3 complex on T cells and possesses structural and functional characteristics of the recently developed BiTE technology. An EphA2-specific single-chain antibody was selected for recognition of an epitope that is preferentially exposed on malignant cells based on the concept of epitope exclusion; this was fused to a CD3-specific single-chain antibody to generate bscEphA2xCD3. The resultant bscAb redirected unstimulated human T cells to lyse EphA2-expressing tumor cells both in vitro and in vivo. In separate experiments, efficient tumor cell lysis was achieved in vitro at drug concentrations <or=1 microg/mL, at a low T-cell effector-to-tumor target cell ratio (1:1), and with tumor cells that possess few available binding sites (2,400 per cell) for bscEphA2xCD3. Time-lapsed microscopy revealed potent cytotoxic activity of bscEphA2xCD3-activated T cells against monolayers of malignant cells but not against monolayers of nontransformed EphA2-positive cells except at the edges of the monolayer where the target epitope was exposed. BscEphA2xCD3 was also efficacious in human xenograft mouse models modified to show human T-cell killing of tumors. Together, our results reveal opportunities for redirecting the potent activity of cytotoxic T cells towards tumor cells that express selectively accessible epitopes and establish EphA2-specific bscAb molecules as novel and potent therapeutics with selectivity for tumor cells.
authors: Medimmune, Inc., Gaithersburg, Maryland 20878, USA. hammonds@medimmune.com
authors: Scott A
authors: SA
authors: Hammond
authors: Ralf
authors: R
authors: Lutterbuese
authors: Shannon
authors: S
authors: Roff
authors: Petra
authors: P
authors: Lutterbuese
authors: Bernd
authors: B
authors: Schlereth
authors: Elizabeth
authors: E
authors: Bruckheimer
authors: Michael S
authors: MS
authors: Kinch
authors: Steve
authors: S
authors: Coats
authors: Patrick A
authors: PA
authors: Baeuerle
authors: Peter
authors: P
authors: Kufer
authors: Peter A
authors: PA
authors: Kiener
mesh_terms: D000818:Animals; D018033:Antibodies, Bispecific / Q000276:immunology / Q000494:pharmacology*; D000918:Antibody Specificity; D017252:CD3 Complex / Q000276:immunology*; D016466:CHO Cells; D048708:Cell Growth Processes / Q000276:immunology; D045744:Cell Line, Tumor; D006224:Cricetinae; D003412:Cricetulus; D000939:Epitopes / Q000276:immunology; D006801:Humans; D007116:Immunization, Passive / Q000379:methods*; D007365:Intercellular Junctions / Q000276:immunology; D008213:Lymphocyte Activation; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D009369:Neoplasms / Q000276:immunology / Q000473:pathology / Q000628:therapy*; D036104:Receptor, EphA2 / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology; D023041:Xenograft Model Antitumor Assays
chemical_list: D018033:Antibodies, Bispecific; D017252:CD3 Complex; D000939:Epitopes; D036104:Receptor, EphA2