TfR-Binding Protein Conjugates for Brain Delivery Without Degradation
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Solution Overview
Problem
Existing methods for delivering drugs to the brain face challenges such as high-affinity binding to the transferrin receptor (TfR) leading to intracellular degradation and reduced brain uptake, and inefficient crossing of the blood-brain barrier.
Innovation Solution
Development of protein-drug conjugates with antigen-binding proteins that bind specifically to human transferrin receptor (TfR) with varying affinities, including specific antibody fragments like scFv, Fab, and Fab'2, to facilitate targeted delivery across the blood-brain barrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-affinity binding to TfR is used to enhance drug delivery to the brain, then brain uptake is improved, but intracellular degradation increases and brain TfR levels are reduced
Solution Approach 1:
The patent applies parameter changes by modifying the binding affinity of the antigen-binding protein to TfR. Instead of using very high affinity (low KD), the invention uses moderate affinity (KD of 10^-6 to 10^-9 M), which is sufficient for BBB transport but low enough to allow efficient release and recycling in the brain, thereby avoiding intracellular degradation while maintaining brain uptake efficacy.
Solution Approach 2:
The invention employs dynamics by creating a reversible binding system that adapts to different physiological conditions. The antigen-binding protein dynamically adjusts its interaction with TfR based on pH and iron content, allowing efficient binding at the BBB for transport, then reversible release in the brain for recycling, thus preventing degradation while maintaining delivery efficiency.
2Speed
If high-affinity antibody binding to TfR is used to cross the BBB, then transport efficiency is improved, but the antibody does not recycle out of the brain
Solution Approach 1:
The patent changes the binding affinity parameter to a moderate range (KD of 10^-6 to 10^-9 M) that allows the antigen-binding protein to efficiently cross the BBB while maintaining the ability to recycle. This moderate affinity is lower than high-affinity antibodies but sufficient for transport, and enables reversible binding for recycling, unlike high-affinity antibodies that become trapped in the brain.
Solution Approach 2:
The invention implements dynamic reversibility in the antigen-binding protein's interaction with TfR. The binding is dynamically reversible under brain conditions (pH and iron content changes), allowing the protein to recycle back across the BBB. This dynamic behavior contrasts with high-affinity antibodies that exhibit irreversible binding and cannot recycle.
3Reliability
If moderate-affinity binding is used to avoid intracellular degradation, then brain uptake and recycling are improved, but binding strength is reduced
Solution Approach 1:
The patent optimizes the binding affinity parameter to a moderate range (KD of 10^-6 to 10^-9 M) that balances two opposing requirements: sufficient strength to ensure efficient BBB transport, but not so strong as to cause intracellular degradation or prevent recycling. This moderate affinity represents an optimal parameter setting that satisfies both constraints simultaneously.
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
Enhances drug delivery to the brain by avoiding intracellular degradation and improving uptake, thereby increasing the efficacy of therapeutic agents.
Implementation Method 1
an antigen-binding protein that binds specifically to human transferrin receptor (TfR)
Data Source
AI summary
The present invention provides, in part, protein-drug conjugates comprising an anti-transferrin receptor (e.g., human transferrin receptor) antigen-binding protein (e.g., scFv, Fab) conjugated to a molecular cargo (e.g., polynucleotides, liposomes or lipid nanoparticles) for delivery of the molecular cargo to a targeted tissue (e.g., brain or muscle). Methods for treating various diseases or disorders, such as neurological diseases or muscular diseases, with the conjugates are provided.