Bivalent Binding Member Expression in Nervous System
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Solution Overview
Problem
Current antibody therapies for Alzheimer's disease face challenges such as the blood-brain barrier restricting the transport of large biomolecules, leading to adverse reactions and the need for high doses and long-term patient engagement, as well as limitations in gene-based delivery methods like AAV-mediated expression of immunoglobulins or scFv proteins, which result in reduced efficacy and toxicity.
Innovation Solution
A method for expressing a bivalent binding member in cells of the nervous system using an expression cassette encoding an antibody heavy chain variable domain, light chain variable domain, and IgG Fc region, forming a disulfide-bonded homodimer that specifically binds to target proteins like amyloid beta, while avoiding binding to Fc gamma receptors to reduce toxicity and enhance half-life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If passive immunotherapy with anti-Aβ antibodies is administered at high doses to overcome blood-brain barrier restriction, then therapeutic levels in the brain are achieved, but adverse reactions including amyloid-related imaging abnormalities and local inflammation occur
Solution Approach 1:
The patent uses the blood-brain barrier itself as an intermediary by exploiting FcRn-mediated transcytosis. The engineered antibody's Fc region binds to FcRn on the luminal side of endothelial cells, enabling active transport across the barrier. This converts the barrier from an obstacle into a delivery mechanism, achieving brain penetration without high peripheral doses and avoiding associated adverse reactions.
Solution Approach 2:
The patent modifies the antibody's Fc region parameters by introducing mutations (e.g., L234A, L235A, N297A) that selectively alter FcRn binding affinity and FcγR interaction. These parameter changes enable the antibody to be recognized by FcRn for transcytosis while reducing binding to FcγR, thereby avoiding inflammatory responses and achieving safe brain delivery.
2Duration of action of moving object
If long-term passive immunotherapy is maintained to sustain therapeutic levels, then patient engagement and compliance are required, but treatment cost and complexity increase
Solution Approach 1:
The patent enables the body's own cells (endothelial cells expressing FcRn) to perform the delivery service. By engineering the antibody to bind FcRn, the therapy exploits the body's existing transcytosis machinery to continuously deliver antibody into the brain, reducing the need for frequent high-dose administrations and improving treatment sustainability.
Solution Approach 2:
The patent achieves continuous therapeutic presence in the brain by leveraging the constitutive expression of FcRn on endothelial cells. The FcRn-mediated transcytosis operates continuously, maintaining steady-state antibody levels in the brain without requiring intermittent high-dose bolus administrations, thereby simplifying the treatment regimen.
3Ease of manufacture
If gene-based delivery of scFv proteins is used to circumvent the blood-brain barrier, then production of therapeutic protein within neuronal cells is achieved, but affinity is substantially lost due to loss of valency
Solution Approach 1:
The patent merges the advantages of scFv (gene-based delivery, intracellular production) with the advantages of full IgG (bivalency, high affinity). By constructing a single-chain antibody that retains both variable domains (VH and VL) connected by a linker, the invention preserves the antigen-binding site's bivalent architecture, maintaining high affinity while enabling gene-based delivery to the CNS.
4Device complexity
If Fc region is removed from scFv to simplify structure, then production is facilitated, but FcRn binding is lost causing shorter half-life and reduced efflux of antigen-bound scFvs from the brain
Solution Approach 1:
The patent extracts only the essential Fc region functionality needed for FcRn binding and bivalent antigen recognition, while removing unnecessary complexity. By using a single-chain variable fragment connected to a simplified Fc region, the invention retains the critical FcRn interaction capability for brain efflux and half-life extension, while maintaining simpler structure and production characteristics compared to full IgG.
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
This approach achieves higher yield and lower toxicity compared to conventional methods, with sustained expression and secretion of therapeutic antibodies in the brain, effectively targeting and reducing amyloid plaques in Alzheimer's disease models, demonstrating potential for durable and safe treatment of neurodegenerative diseases.
Implementation Method 1
two molecules of the polypeptide form a disulfide-bonded homodimeric bivalent binding member specific for the target protein
Implementation Method 2
Removal of the Fc region also results in a loss of FcRn binding, causing shorter half-life in the periphery and reduced efflux of antigen (Ag)-bound scFvs from the brain via reverse transcytosis
Data Source
AI summary
Provided herein are recombinant vectors that express bivalent binding members and methods of using the vectors to modify cells of the nervous system to express the binding members in the brain of patients having a neurological disease such as a neurodegenerative disease.