FcRn Antagonist Variant Reducing IgG Serum Levels
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Solution Overview
Problem
Current methods for treating antibody-mediated disorders, such as autoimmune diseases, are inadequate in effectively reducing serum levels of IgG antibodies, which are prolonged due to binding with FcRn, leading to prolonged half-life and excessive levels that contribute to disease pathology.
Innovation Solution
Administration of an isolated FcRn-antagonist with increased affinity and reduced pH dependence, specifically binding to FcRn, to reduce serum levels of Fc-containing agents like antibodies and immunoadhesins, using a variant Fc region with specific amino acid sequences and dosing regimens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If IgG binds to FcRn, then serum half-life is prolonged, but serum levels become excessively high contributing to disease pathology
Solution Approach 1:
The patent applies preliminary anti-action by administering FcRn antagonists before or during the period when IgG levels would naturally accumulate and cause pathology. The antagonists preemptively block the FcRn-IgG binding interaction, preventing the protective recycling that would otherwise lead to excessive IgG accumulation in autoimmune diseases and other antibody-mediated disorders.
Solution Approach 2:
The patent employs parameter changes by modifying the binding characteristics of FcRn antagonists to achieve pH-dependent binding with increased affinity at acidic endosomal pH and decreased affinity at physiological pH. This parameter optimization allows selective interference with IgG recycling while minimizing non-specific effects, thereby controlling serum IgG levels without completely eliminating the half-life extension mechanism.
2Reliability
If FcRn binding affinity is increased, then IgG protection from degradation is enhanced, but pH dependence increases leading to less selective binding
Solution Approach 1:
The patent optimizes the binding parameters of FcRn antagonists by engineering variant Fc regions with specific amino acid substitutions (e.g., at positions 239, 241, 332, 333, 433, 434, 436) that tune the pH-dependence curve. These modifications increase binding affinity at acidic pH (enhancing protective function) while decreasing affinity at physiological pH (reducing non-specific binding), thereby achieving selective and controllable FcRn interaction.
3Reliability
If existing FcRn antagonists are used (blocking antibodies, peptides, or wild-type IgG), then IgG binding to FcRn is inhibited, but binding affinity is insufficient and pH dependence is not optimized
Solution Approach 1:
The patent achieves superior binding characteristics by engineering variant Fc regions with multiple amino acid substitutions that collectively optimize both binding affinity and pH dependence. The coordinated modifications at specific positions create synergistic effects that enhance FcRn binding at acidic pH while maintaining selectivity, overcoming the limitations of wild-type IgG and previously described antagonists.
Solution Approach 2:
The patent creates a composite Fc region structure combining multiple engineered amino acid variants within a single Fc domain. This composite design integrates several beneficial mutations (e.g., L239Q, N241Q, S332P, T333P, and others) that individually contribute to enhanced FcRn binding and optimized pH dependence, resulting in a synergistic effect greater than the sum of individual mutations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The FcRn-antagonist effectively reduces serum levels of Fc-containing agents, providing a therapeutic approach for antibody-mediated disorders by inhibiting their binding to FcRn, thereby shortening their half-life and alleviating disease symptoms.
Implementation Method 1
This recycling is facilitated by the pH dependent binding of IgG to FcRn, where the IgG/FcRn interaction is stronger at acidic endosomal pH than at extracellular physiological pH.
Implementation Method 2
the FcRn-antagonist binds specifically to FcRn with increased affinity and reduced pH dependence relative to the native Fc region
Data Source
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AI summary
Provided are novel methods of reducing the serum levels of Fc-containing agents (e.g., antibodies and immunoadhesins) in a subject. These methods generally comprise administering to the subject an effective amount of an isolated FcRn-antagonist that binds specifically to FcRn with increased affinity and reduced pH dependence relative to the native Fc region. The disclosed methods are particularly useful for treating antibody-mediated disorders (e.g. autoimmune diseases).