title: CD3 x CD28 cross-interacting bispecific antibodies improve tumor cell dependent T-cell activation.
abstract: Bispecific antibodies (Bs-Abs) containing an anti-CD3 and an anti-TAA specificity can recruit T cells to the tumor for cancer immunotherapy. To be effective, efficient activation at the tumor site is a prerequisite. This can be achieved by triggering both the T-cell receptor and the co-stimulatory molecule CD28. We engineered two recombinant cross-interacting Bs-Abs (CriBs-Abs) by incorporating a peptide tag and its cognate single-chain variable fragment (scFv), respectively, into a pair of (tumor x CD3) and (tumor x CD28) binding Bs-Abs. A 30-fold lower concentration of the activating CriBs-Ab as compared to non interacting Bs-Ab was sufficient for strong T-cell activation in the presence of tumor cells. One thousand-fold higher concentrations of both CriBs-Abs were required for marginal T-cell activation (70-fold below maximal response) in the absence of tumor cells. An optimized stoichiometry (1 : 1000) of activating versus co-stimulating CriBs-Ab thus allowed low doses of activating CriBs-Ab to induce tumor-cell dependent T-cell activation when used in combination with high concentrations of the pre-targeted co-stimulating CriBs-Ab in vitro. This indicates a large window of operation in which only tumor cell dependent T-cell activation is induced and systemic tumor cell independent T-cell activation is avoided, while ensuring optimal activation with a low concentration of the activating CriBs-Ab, which has the highest potential to induce toxic effects in vivo.
authors.affiliation: Flanders Interuniversity Institute for Biotechnology (VIB), Department for Molecular Biomedical Research, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium.
authors.forename: An
authors.initials: A
authors.lastname: Willems
authors.forename: Steve
authors.initials: S
authors.lastname: Schoonooghe
authors.forename: Dominique
authors.initials: D
authors.lastname: Eeckhout
authors.forename: Geert
authors.initials: G
authors.lastname: De Jaeger
authors.forename: Johan
authors.initials: J
authors.lastname: Grooten
authors.forename: Nico
authors.initials: N
authors.lastname: Mertens
mesh_terms: D000818:Animals; D018033:Antibodies, Bispecific / Q000276:immunology / Q000627:therapeutic use*; D018106:CD28 Antigens / Q000276:immunology*; D017252:CD3 Complex / Q000276:immunology*; D002460:Cell Line; D005260:Female; D006801:Humans; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D009369:Neoplasms / Q000276:immunology / Q000628:therapy*; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D018033:Antibodies, Bispecific; D018106:CD28 Antigens; D017252:CD3 Complex