La presente invention concerne des preparations pharmaceutiques pour le traitement d'une tumeur epitheliale chez un humain, ladite preparation pharmaceutique comprenant un anticorps a chaine unique bi-specifique presentant un premier domaine de liaison se liant specifiquement au CD3 humain, et un second domaine de liaison se liant specifiquement a l'ACE humain, ledit second domaine de liaison comprenant au moins une partie du CDR-H3 ou la totalite du CDR-H3 de l'anticorps monoclonal murin A5B7. En outre, la presente invention concerne des procedes de production desdites preparations pharmaceutiques, ainsi que des applications medicales/pharmaceutiques des molecules d'anticorps a chaine unique bi-specifiques portant des domaines specifiques vis-a-vis de l'antigene CD3 humain et de l'antigene ACE humain.

Bispecific single-chain antibody constructs specific for human CD3 have been extensively studied for antitumor activity in human xenograft models using severe combined immunodeficient mice supplemented with human T cells. High efficacy at low effector-to-target ratios, independence of T cell costimuli and a potent activation of previously unstimulated polyclonal T cells were identified as hallmarks of this class of bispecific antibodies. Here we studied a bispecific single-chain antibody construct (referred to as ‘bispecific T cell engager’, BiTE) in an immunocompetent mouse model. This was possible by the use of a murine CD3-specific BiTE, and a syngeneic melanoma cell line (B16F10) expressing the human Ep-CAM target. The murine CD3-specific BiTE, called 2C11x4-7 prevented in a dose-dependent fashion the outgrowth of subcutaneously growing B16/Ep-CAM tumors with daily i.v. injections of 5 or 50 μg BiTE which was most effective. Treatment with 2C11x4-7 was effective even when it was started 10 days after tumor cell inoculation but delayed treatments showed a reduction in the number of cured animals. 2C11x4-7 was also highly active in a lung tumor colony model. When treatment was started on the day of intravenous tumor cell injection, seven out of eight animals stayed free of lung tumors, and three out of eight animals when treatment was started on day 5. Our study shows that BiTEs also have a high antitumor activity in immunocompetent mice and that there is no obvious need for costimulation of T cells by secondary agents.

Extract: While monoclonal antibodies closely resemble the naturally occurring immune defense proteins, bispecific antibodies (i.e., antibodies detecting two different antigens) are not found in nature. Both types of antibodies share the feature of antigen specificity that is mediated by the presence of a unique antigen binding site on the antibody. Antigen binding sites exclusively interact with a particular molecular part of an antigen, known as an epitope. Monoclonal IgG (immunoglobulin G) antibodies carry two antigen binding sites for the same epitope, while bispecific antibodies are equipped with two different antigen binding sites with the potential to link two epitopes that could be present on two different cell types. Murine monoclonal antibodies first became available through the hybridoma technology developed by Köhler and Milstein in 1975. Since then they have been improved for therapeutic use by chimerization (only the antigen binding sites remain murine, all other antibody parts are of human origin, e.g., Erbitux), humanization (only the six subregions of the antigen binding site that actually contact the epitope remain murine, e.g., Avastin) or the recovery of fully human antibodies from phage display libraries or from mice transgenic for human immunoglobulin genes (e.g., ABX-EGF, an investigational drug). Several monoclonal antibodies have been approved for human therapy in various disease indications acting either as receptor antagonists, neutralizers of protein receptor ligands or through the recruitment of immune effector functions against pathogenic cells.

We have recently demonstrated that a recombinant single-chain bispecific Ab construct, bscCD19xCD3, in vitro induces rapid B lymphoma-directed cytotoxicity at picomolar concentrations with unstimulated peripheral T cells. In this study, we show that treatment of nonobese diabetic SCID mice with submicrogram doses of bscCD19xCD3 could prevent growth of s.c. human B lymphoma xenografts and essentially cured animals when given at an early tumor stage. The effect was dose dependent, dependent on E:T ratio and the time between tumor inoculation and administration of bscCD19xCD3. No therapeutic effect was seen in the presence of human lymphocytes alone, a vehicle control, or with a bispecific single-chain construct of identical T cell-binding activity but different target specificity. In a leukemic nonobese diabetic SCID mouse model, treatment with bscCD19xCD3 prolonged survival of mice in a dose-dependent fashion. The human lymphocytes used as effector cells in both animal models did not express detectable T cell activation markers at the time of coinoculation with tumor cells. The bispecific Ab therefore showed an in vivo activity comparable to that observed in cell culture with respect to high potency and T cell costimulus independence. These properties make bscCD19xCD3 superior to previously investigated CD19 bispecific Ab-based therapies.