title: Extremely potent, rapid and costimulation-independent cytotoxic T-cell response against lymphoma cells catalyzed by a single-chain bispecific antibody.
abstract: A recent study reported on an anti-CD19/anti-CD3 single-chain bispecific antibody (bscCD19xCD3) exhibiting high activity against human B lymphoma cell lines (Löffler et al., Blood 2000;95:2098-103). In the present study, we have explored in detail the in vitro efficacy, T-cell donor variability, binding characteristics, specificity, kinetics and interleukin-2 (IL-2) dependence of bscCD19xCD3. We found that a majority of human donor T cells tested (n = 86) gave half-maximal B-lymphoma cell lysis (ED(50)) within a range of 10-50 pg/ml bscCD19xCD3, corresponding to sub-picomolar concentrations of the bispecific antibody. Under identical experimental conditions, the anti-CD20 monoclonal antibody rituximab had an at least 100,000-fold lower in vitro efficacy. The extreme potency of bscCD19xCD3 was in sharp contrast to the relatively low affinity of the anti-CD3 and anti-CD19 single-chain Fv portions in K(D) ranges of 10(-7) and 10(-9) M, respectively. Cell lysis by bscCD19xCD3 was predominantly mediated by the population of CD8/CD45RO-positive T cells. Both immortalized CD4- and CD8-positive human T-cell clones were highly active effector cells as well. Cell lysis by bscCD19xCD3 was rapid and specific. The respective parental monoclonal antibodies inhibited cell lysis and CD19-negative cells were not harmed by T cells in the presence of high amounts of bscCD19xCD3. The potent T-cell stimulus IL-2 could not markedly augment the activity of bscCD19xCD3-stimulated T cells. In conclusion, bscCD19xCD3 could redirect unstimulated cytotoxic T cells against CD19-positive cells in an unexpectedly potent, rapid and specific fashion.
authors.affiliation: Micromet AG, Am Klopferspitz 19, 82152 Martinsried, Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Dreier
authors.forename: Grit
authors.initials: G
authors.lastname: Lorenczewski
authors.forename: Christian
authors.initials: C
authors.lastname: Brandl
authors.forename: Patrick
authors.initials: P
authors.lastname: Hoffmann
authors.forename: Uwe
authors.initials: U
authors.lastname: Syring
authors.forename: Frank
authors.initials: F
authors.lastname: Hanakam
authors.forename: Peter
authors.initials: P
authors.lastname: Kufer
authors.forename: Gert
authors.initials: G
authors.lastname: Riethmuller
authors.forename: Ralf
authors.initials: R
authors.lastname: Bargou
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Baeuerle
mesh_terms: D000818:Animals; D018033:Antibodies, Bispecific / Q000378:metabolism*; D000911:Antibodies, Monoclonal / Q000627:therapeutic use; D058846:Antibodies, Monoclonal, Murine-Derived; D018941:Antigens, CD19 / Q000378:metabolism*; D017252:CD3 Complex / Q000378:metabolism*; D016466:CHO Cells; D002469:Cell Separation; D006224:Cricetinae; D004306:Dose-Response Relationship, Immunologic; D005434:Flow Cytometry; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism; D007700:Kinetics; D008213:Lymphocyte Activation; D008223:Lymphoma / Q000378:metabolism*; D051379:Mice; D000069283:Rituximab; D013602:T-Lymphocytes, Cytotoxic / Q000378:metabolism*; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: D018033:Antibodies, Bispecific; D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018941:Antigens, CD19; D017252:CD3 Complex; D007376:Interleukin-2; D000069283:Rituximab