Optimized Fc variants and methods for their generation

Abstract

The present invention relates to optimized Fc variants, methods for their generation, and antibodies and Fc fusions comprising optimized Fc variants.

Description

[0001] This application claims benefit under 35 U.S.C. §199(e) to U.S. Ser. No. 10 / 672,280, filed Sep. 26, 2003, Ser. No. 10 / 379,392, filed Mar. 3, 2003, 60 / 477,839 filed Jun. 12, 2003; 60 / 467,606, filed May 2, 2003; 60 / 414,433 filed Sep. 27, 2002; and 60 / 442,301 filed Jan. 23, 2003, all of which are expressly incorporated by reference in their entirety.FIELD OF THE INVENTION [0002] The present invention relates to novel optimized Fc variants, engineering methods for their generation, and their application, particularly for therapeutic purposes. BACKGROUND OF THE INVENTION [0003] Antibodies are immunological proteins that bind a specific antigen. In most mammals, including humans and mice, antibodies are constructed from paired heavy and light polypeptide chains. Each chain is made up of individual immunoglobulin (Ig) domains, and thus the generic term immunoglobulin is used for such proteins. Each chain is made up of two distinct regions, referred to as the variable and constant re...

AI Technical Summary

Problems solved by technology

Yet another level of complexity is the existence of a number of FcγR polymorphisms in the human proteome.

Despite such widespread use, antibodies are not optimized for clinical use.

Two significant deficiencies of antibodies are their suboptimal anticancer potency and their demanding production requirements.

Despite this arsenal of anti-tumor weapons, the potency of antibodies as anti-cancer agents is unsatisfactory, particularly given their high cost.

In these cases depletion of target cells is undesirable and can be considered a side effect.

Effector function can also be a problem for radiolabeled antibodies, referred to as radioconjugates, and antibodies conjugated to toxins, referred to as immunotoxins.

These drugs can be used to destroy cancer cells, but the recruitment of immune cells via Fc interaction with FcγRs brings healthy immune cells in proximity to the deadly payload (radiation or toxin), resulting in depletion of normal lymphoid tissue along with targeted cancer cells (Hutchins et al., 1995, Proc Natl Acad Sci U S A 92:11980-11984; White et al., 2001, Annu Rev Med 52:125-145).

Antibodies must be expressed in mammalian cells, and the currently marketed antibodies together with other high-demand biotherapeutics consume essentially all of the available manufacturing capacity.

First, it dramatically raises the cost of goods to the producer, a cost that is passed on to the patient.

Second, it hinders industrial production of approved antibody products, limiting availability of high demand therapeutics to patients.

Finally, because clinical trials require large amounts of a protein that is not yet profitable, the insufficient supply impedes progress of the growing antibody pipeline to market.

This may result in reduced or even lack of effector function because, as discussed above, the carbohydrate structure can significantly impact FcγR and complement binding.

A potentially greater problem with nonhuman glycoforms may be immunogenicity; carbohydrates are a key source of antigenicity for the immune system, and the presence of nonhuman glycoforms has a significant chance of eliciting antibodies that neutralize the therapeutic, or worse cause adverse immune reactions.

Thus the efficacy and safety of antibodies produced by transgenic plants and animals remains uncertain.

For complex proteins such as antibodies there are a number of obstacles to bacterial expression, including folding and assembly of these complex molecules, proper disulfide formation, and solubility, stability, and functionality in the absence of glycosylation because proteins expressed in bacteria are not glycosylated.

However the ultimate utility of bacterially expressed antibodies as therapeutics remains hindered by the lack of glycosylation, which results in lack effector function and may result in poor stability and solubility.

This will likely be more problematic for formulation at the high concentrations for the prolonged periods demanded by clinical use.

Yet a substantial obstacle to engineering Fc variants with the desired properties is the difficulty in predicting what amino acid modifications, out of the enormous number of possibilities, will achieve the desired goals, coupled with the inefficient production and screening methods for antibodies.

Indeed one of the principle reasons for the incomplete success of the prior art is that approaches to Fc engineering have thus far involved hit-or-miss methods such as alanine scans or production of glycoforms using different expression strains.

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