Cross-species-specific single domain bispecific single chain antibody

Medicilon's toxicology department has professional teams with rich experience in toxicology studies. We offer high-quality data and rapid turnaround period to support drug discovery and development. Our toxicological studies are conducted in various animal species. The toxicological evaluation from dose design, in-life studies to histology and pathology testing along with toxicokinetics studies are all compliant with GLP or NON-GLP standards. Our study platform is certified as one of the Shanghai Public Service Research Platforms.

The present invention relates to a bispecific single chain antibody molecule comprising a first binding domain consisting of one antibody variable domain capable of binding to an epitope of the human and non-chimpanzee primate CD3 epsilon chain, wherein the epitope is part of an amino acid sequence comprised in the group consisting of SEQ ID NOs. 2, 4, 6, and 8, and a second binding domain capable of binding to an epitope of a human and a non-chimpanzee primate tumor target antigen. The invention further relates to a bispecific single chain antibody molecule comprising a first binding domain capable of binding to an epitope of human and non- chimpanzee primate CD3ε (epsilon) chain, wherein the epitope is part of an amino acid sequence comprised in the group consisting of SEQ ID NOs. 2, 4, 6, and 8, and a second binding domain consisting of one antibody variable domain capable of binding to an epitope of a human and a non-chimpanzee primate tumor target antigen. The invention also provides nucleic acids encoding said bispecific single chain antibody molecule as well as vectors and host cells and a process for its production. The invention further relates to pharmaceutical compositions comprising said bispecific single chain antibody molecule and medical uses of said bispecific single chain antibody molecule.

The discriminatory ability, i.e. the species specificity, inherent not only to CD3 monoclonal antibodies (and fragments thereof), but to monoclonal antibodies in general, is a significant impediment to their development as therapeutic agents for the treatment of human diseases. In order to obtain market approval any new candidate medication must pass through rigorous testing. This testing can be subdivided into preclinical and clinical phases: Whereas the latter - further subdivided into the generally known clinical phases I, Il and III - is performed in human patients, the former is performed in animals. The aim of pre-clinical testing is to prove that the drug candidate has the desired activity and most importantly is safe. Only when the safety in animals and possible effectiveness of the drug candidate has been established in preclinical testing this drug candidate will be approved for clinical testing in humans by the respective regulatory authority. Drug candidates can be tested for safety in animals in the following three ways, (i) in a relevant species, i.e. a species where the drug candidates can recognize the ortholog antigens, (ii) in a transgenic animal containing the human antigens and (iii) by use of a surrogate for the drug candidate that can bind the ortholog antigens present in the animal. Limitations of transgenic animals are that this technology is typically limited to rodents. Between rodents and man there are significant differences in the physiology and the safety results cannot be easily extrapolated to humans. The limitations of a surrogate for the drug candidate are the different composition of matter compared to the actual drug candidate and often the animals used are rodents with the limitation as discussed above. Therefore, preclinical data generated in rodents are of limited predictive power with respect to the drug candidate. The approach of choice for safety testing is the use of a relevant species, preferably a lower primate. The limitation now of monoclonal antibodies suitable for therapeutic intervention in man described in the art is that the relevant species are higher primates, in particular chimpanzees. Chimpanzees are considered as endangered species and due to their human-like nature, the use of such animals for drug safety testing has been banned in Europe and is highly restricted elsewhere. CD3 has also been successfully used as a target for bispecific single chain antibodies in order to redirect cytotoxic T cells to pathological cells, resulting in the depletion of the diseased cells from the respective organism (WO 99/54440; WO 04/106380). For example, Bargou et al. (Science 321 (2008): 974-7) have recently reported on the clinical activity of a CD19xCD3 bispecific antibody construct called blinatumomab, which has the potential to engage all cytotoxic T cells in human patients for lysis of cancer cells. Doses as low as 0.005 milligrams per square meter per day in non-Hodgkin's lymphoma patients led to an elimination of target cells in blood. Partial and complete tumor regressions were first observed at a dose level of 0.015 milligrams, and all seven patients treated at a dose level of 0.06 milligrams experienced a tumor regression. Blinatumomab also led to clearance of tumor cells from bone marrow and liver. Though this study established clincical proof of concept for the therapeutic potency of the bispecific single chain antibody format in treating blood-cell derived cancer, there is still need for successful concepts for therapies of other cancer types.

In the event that a bispecific antibody is intended for therapeutic use, it is desirable to produce high amounts of this antibody solubly and in the desired functional form. The production of functionally active antibody becomes especially critical when producing bispecific antibodies of which one portion is able to activate and recruit the cytotoxic potential of human immune effector cells. For example, a produced antibody devoid of functional activity will not lead to the desired activation of human immune effector cells, while a bispecific antibody which is functionally active, albeit not in the desired manner, as for example may be the case when the bispecific antibody is produced in a heterogeneous form containing multiple isomers, may activate and recruit the cytotoxic potential of human immune effector cells in unforeseeable and/or unintended manners.

One example of the sort of unintended activation mentioned above is the possibility of activation of human immune effector cells to exert an effect on other human immune effector cells instead of on a target cell intended for destruction. This type of immune effector cell fratricide may jeopardize the effectiveness of a regimen of therapy depending on the activity of human immune effector cells.