Engineered LDLR Variants Resist PCSK9 Degradation
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Solution Overview
Problem
Current treatments for familial hypercholesterolemia, such as LDL apheresis and cholesterol-lowering drugs, have limitations including substantial morbidity and mortality associated with orthotopic liver transplantation, and existing gene therapies require high doses of adeno-associated viral vectors to achieve significant cholesterol reduction.
Innovation Solution
Engineered human low-density lipoprotein receptor (hLDLR) variants with reduced affinity for PCSK9 and/or IDOL, characterized by increased systemic half-life, are delivered via recombinant adeno-associated virus vectors to lower cholesterol levels, overcoming degradation pathways and achieving sustained efficacy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high doses of adeno-associated viral vectors are used to achieve significant cholesterol reduction, then cholesterol lowering efficacy is improved, but vector dose requirements increase leading to increased injection volume, toxicity, immune response, and manufacturing costs
Solution Approach 1:
The patent applies parameter changes by modifying the amino acid sequence of the LDLR protein to create variants with altered properties. Specifically, mutations are introduced in the PCSK9 binding domain (residues 290-320) and IDOL binding domain (residues 790-820) to reduce affinity for these degradation pathways, thereby increasing receptor stability and half-life without requiring higher vector doses
Solution Approach 2:
The patent creates LDLR variants that are more stable and resistant to degradation, effectively making the therapeutic protein last longer in the body. This extends the functional lifetime of the expressed receptor, reducing the need for repeated high-dose vector administrations and lowering overall treatment costs
2Reliability
If wild-type LDLR is used in gene therapy, then cholesterol levels can be reduced, but the receptor is rapidly degraded by PCSK9 and IDOL pathways limiting efficacy and duration
Solution Approach 1:
The patent converts the harmful degradation pathways into beneficial selectivity by designing LDLR variants that specifically avoid PCSK9 and IDOL-mediated degradation. The mutations in the binding domains prevent recognition by these proteases, transforming the previously harmful rapid degradation into a beneficial extended half-life and sustained cholesterol lowering effect
Solution Approach 2:
The patent changes the biochemical parameters of the LDLR protein by introducing specific amino acid mutations that alter the binding affinity for PCSK9 and IDOL. These parameter changes in the protein structure result in increased stability and extended functional duration of the receptor in the liver
Data Source
AI summary
A recombinant vector having an expression cassette is provided which comprises a modified human low density lipoprotein receptor (hLDLR) gene is provided, wherein said hLDLR gene encodes a modified hLDLR comprising (a) one or more of the following amino acid substitutions: L318H, N295D, H306D, V307D, N309A, D310N, L318H, and/or L318D; or (b) an amino acid substitution of any of (a) in combination with one or more of the following amino acid substitutions: K796, K809R and/or C818A. Also provided are pharmaceutical compositions containing this vector and uses therefor in lowering cholesterol and/or treating familial hypercholesterolemia.