La presente invention concerne un polypeptide comprenant un premier domaine de liaison humain capable de se fixer a un epitope de la chaine (epsilon) du CD3 humain ou d'un primate autre que le chimpanze, un second domaine de liaison capable de se fixer au recepteur EGF, au recepteur Her2/neu ou a l'IgE d'un humain et/ou d'un primate autre que le chimpanze, ainsi qu'un procede destine a la production de ce polypeptide. L'invention concerne egalement des acides nucleiques codant pour le polypeptide, des vecteurs comprenant ces acides nucleiques et des cellules hotes comprenant le vecteur. Dans un autre aspect, l'invention concerne une composition pharmaceutique comprenant ledit polypeptide et des applications medicales du polypeptide.

We have compared the cytotoxic activity of rituximab with that of blinatumomab (MT103/MEDI-538), a single-chain CD19-/CD3-bispecific antibody engaging human T cells. Blinatumomab consistently led to a higher degree of lysis of human lymphoma lines than rituximab, and was active at much lower concentration. The cytotoxicity mediated by blinatumomab and rituximab both caused a potent activation of pro-caspases 3 and 7 in target cells, a key event in induction of granzyme-mediated apoptotic cell death. Combination of rituximab with blinatumomab was found to greatly enhance the activity of rituximab, in particular at low effector-to-target cell ratios and at low antibody concentration.

2402 Monoclonal IgG1 antibodies cetuximab and trastuzumab have become standard of care for the treatment of patients with advanced colon and breast cancer, respectively. Mode of action of these antibodies includes inhibition of signalling and antibody-dependent cellular cytotoxicity (ADCC). Numerous efforts are ongoing to increase the anti-tumor activity of therapeutic antibodies, which typically require weekly doses of 2-8 mg/kg and show only limited efficacy as monotherapy in metastatic disease. Conventional antibodies such as cetuximab and trastuzumab cannot directly engage T cells, which are considered the most potent cytotoxic cells in the organism. This is because T cells lack antibody-binding Fcγ receptors. We have developed so called BiTE antibodies that can redirect T cells --irrespective of T cell receptor specificity and peptide antigen presentation-- to tumor cells expressing a particular surface antigen.
 Here, we have converted both cetuximab and trastuzumab into T cell-engaging BiTE antibodies. Respective single-chain antibodies were crafted from the variable domains of cetuximab and trastuzumab and genetically linked to anti-CD3 single-chain antibodies that confer the particular T cell-engaging properties of BiTE antibodies. The resulting EGFR- and HER-2-specific BiTE antibodies were stable 55 kDa proteins with binding specificity to EGFR and HER-2 on tumor cells, respectively, and to CD3 on T cells. Both showed potent redirected lysis of EGFR- and HER-2-expressing target cell lines by peripheral human T cells at half maximal concentrations of 0.1-0.2 ng/ml (ca. 2-4 picomolar). Redirected lysis was highly specific for target antigens. Concomitant T cell activation was only observed in the presence of target cells but not when cetuximab- and trastuzumab-based BiTE antibodies were incubated with T cells alone.
 The anti-tumor activity of cetuximab and trastuzumab was directly compared with that of the corresponding BiTE antibodies in cytotoxicity assays using identical assay conditions and the same donors as source for peripheral mononuclear effector cells (PBMC). BiTE antibodies consistently showed a higher activity than the conventional antibodies. In contrast to the IgG1 antibodies, the BiTE antibodies led to a complete lysis of target cells during the assay period. Data from animal models will be presented that compare the efficacy of cetuximab and trastuzumab side-by-side with that of respective BiTE antibodies.
 Our data show that established therapeutic monoclonal antibodies can be successfully converted into BiTE antibodies, with the potential to engage T cells for highly potent and strictly target-dependent tumor cell elimination.

Inhibition of the interleukin-2 (IL-2) pathway has potent immunosuppressive activity in humans as is evident from the broad therapeutic utility of cyclosporine, rapamycin, tacrolimus, and monoclonal antibodies blocking the high-affinity subunit of the IL-2 receptor (CD25). Here we describe a humanized antibody, MT204, interfering with IL-2 signaling by a novel mechanism. Although MT204 did not prevent IL-2 from binding to CD25, it potently antagonized downstream signaling events of IL-2 at sub-nanomolar concentrations, such as STAT3 tyrosine phosphorylation, expression of CD124, production of γ-interferon and cell proliferation. While MT204 and the anti-CD25 mAb daclizumab were equally effective in inhibiting autocrine growth of human CD4+ T cells, MT204 was far superior in preventing proliferation of NKL lymphoma cells, production of γ-interferon by natural killer (NK) cells and proliferation of primary NK cells. MT204 has potential as a novel immunosuppressive and anti-proliferative therapy with an apparently broader spectrum of activities than anti-CD25 antibodies.