Binding domain-immunoglobulin fusion proteins

Abstract

The invention relates to novel binding domain-immunoglobulin fusion proteins that feature a binding domain for a cognate structure such as an antigen, a counterreceptor or the like, a hinge region polypeptide having either zero or one cysteine residue, and immunoglobulin CH2 and CH3 domains, and that are capable of ADCC and / or CDC while occurring predominantly as monomeric polypeptides. The fusion proteins can be recombinantly produced at high expression levels. Also provided are related compositions and methods, including immunotherapeutic applications.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of U.S. application Ser. No. 10 / 053,530, filed Jan. 17, 2002, now pending, which claims the benefit of priority of U.S. Provisional Application No. 60 / 367,358 (formerly U.S. Ser. No. 09 / 765,208, filed Jan. 17, 2001), the contents of which are incorporated by reference in their entirety.BACKGROUND OF THE INVENTION [0002] The present invention relates generally to immunologically active, recombinant binding proteins, and in particular, to molecularly engineered binding domain-immunoglobulin fusion proteins, including single chain Fv-immunoglobulin fusion proteins. The present invention also relates to compositions and methods for treating malignant conditions and B-cell disorders, including diseases characterized by autoantibody production. [0003] An immunoglobulin molecule is composed of two identical light chains and two identical heavy chains that are joined into a macromolecular complex by interchain...

AI Technical Summary

Benefits of technology

"The present invention provides a binding domain-immunoglobulin fusion protein that has immunological activity and can specifically bind to an antigen. The fusion protein comprises a binding domain polypeptide that is fused to an immunoglobulin hinge region polypeptide that does not have any cysteine residues. The hinge region polypeptide can be mutated or derived from a wild-type immunoglobulin hinge region polypeptide. The binding domain polypeptide can be an immunoglobulin light chain or heavy chain variable region polypeptide. The fusion protein can be used for treating malignant conditions or B-cell disorders."

Problems solved by technology

Despite the advantages that scFv molecules bring to serotherapy, several drawbacks to this therapeutic approach exist.

While rapid clearance of scFv may reduce toxic effects in normal cells, such rapid clearance may prevent delivery of a minimum effective dose to the target tissue.

Manufacturing adequate amounts of scFv for administration to patients has been challenging due to difficulties in expression and isolation of scFv that adversely affect the yield.

During expression, scFv molecules lack stability and often aggregate due to pairing of variable regions from different molecules.

Furthermore, production levels of scFv molecules in mammalian expression systems are low, limiting the potential for efficient manufacturing of scFv molecules for therapy (Davis et al, J. Biol. Chem. 265:10410-18 (1990); Traunecker et al., EMBO J.

Conjugation or fusion of toxins to scFV provides a very potent molecule, but dosing is limited by toxicity from the toxin molecule.

In addition, immunotoxins are highly immunogenic, and host antibodies generated against the toxin limit its potential for repeated treatment.

An additional disadvantage to using scFv for therapy is the lack of effector function.

An scFv without the cytolytic functions, ADCC and complement dependent-cytotoxicity (CDC), associated with the constant region of an immunoglobulin may be ineffective for treating disease.

Even though development of scFv technology began over 12 years ago, currently no scFv products are approved for therapy.

Although remission rates have increased, most patients still relapse and succumb to their disease.

Barriers to cure with cytotoxic drugs include tumor cell resistance and the high toxicity of chemotherapy, which prevents optimal dosing in many patients.

Thus, the choice of surface idiotype for therapy of B cell malignancy has been limited by the outgrowth of tumor cell variants with altered surface idiotype expression even though the antigen exhibits a high degree of tumor selectivity (Meeker et al., N. Engl. J. Med.

Shedding or internalization of a target antigen after an immunoglobulin binds to the antigen may allow tumor cells to escape destruction, thus limiting the effectiveness of serotherapy.

However, tumor relapse commonly occurs within six months to one year.

While the effectiveness of therapy is increased, associated toxicity from the long in vivo half-life of the radioactive antibody increased also, sometimes requiring that the patient undergo stem cell rescue (Press et al., N. Eng. J. Med.

However, the advantages of effector functions, including complement fixation and ADCC, that are provided by the Fc region of the CD20 mAb are lost.

However, after treatment is completed, normal B cells are regenerated from CD20 negative B cell precursors; therefore, patients treated with anti-CD20 therapy do not experience significant immunosuppression.

The large size of Rituximab™ prevents optimal diffusion of the molecule into lymphoid tissues that contain malignant B cells, thereby limiting these anti-tumor activities.

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