Factor VIII–VWF Chimeric Proteins for Extended Half-Life
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Solution Overview
Problem
Current FVIII products for treating hemophilia A have a short half-life, requiring frequent intravenous administration, and existing extensions, such as pegylation and glycopegylation, only provide limited improvements.
Innovation Solution
A chimeric protein is developed by fusing Factor VIII (FVIII) with von Willebrand Factor (VWF) through an XTEN sequence, where the XTEN sequence contains less than 288 amino acids, and optionally using Ig constant regions and cleavable linkers to enhance stability and prolong half-life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If FVIII is fused with VWF through XTEN sequence to extend half-life, then duration of action is improved, but molecular weight and structural complexity increase
Solution Approach 1:
The VWF protein is segmented to include only the D' and D3 domains rather than the full-length VWF, reducing the molecular weight while maintaining the half-life extension function. The XTEN sequence acts as a modular linker that can be independently optimized for length and composition.
Solution Approach 2:
The XTEN sequence is strategically positioned between FVIII and the VWF D' domain to provide localized properties that enhance solubility and stability without contributing to the overall molecular weight burden. The specific amino acid composition of XTEN (rich in serine, threonine, and glycine) provides local quality improvements.
2Duration of action of moving object
If FVIII is fused with VWF through XTEN sequence to extend half-life, then duration of action is improved, but device complexity increases
Solution Approach 1:
Multiple functional elements (FVIII, XTEN sequence, VWF D' domain, and Ig constant region) are merged into a single chimeric protein construct, simplifying the overall treatment regimen by combining half-life extension, stability, and therapeutic functions in one molecule.
Solution Approach 2:
The chimeric protein combines different protein domains with distinct properties: FVIII provides therapeutic activity, XTEN provides solubility and stability, VWF D' domain provides half-life extension through FcRn interaction, and Ig constant region provides additional stability and reduced immunogenicity.
3Ease of manufacture
If XTEN sequence with less than 288 amino acids is used, then ease of manufacture is improved, but duration of action may be limited
Solution Approach 1:
The XTEN sequence length is optimized within a specific range (less than 288 amino acids) to balance manufacturing ease with sufficient half-life extension. The amino acid composition and sequence of XTEN are specifically designed to achieve the desired pharmacokinetic properties without excessive length.
Solution Approach 2:
The XTEN sequence acts as an intermediary element that mediates between the therapeutic FVIII domain and the half-life extension VWF D' domain, providing a flexible linker that facilitates proper folding and stability while maintaining manufacturability.
Data Source
AI summary
The present invention provides a chimeric protein comprising a first polypeptide which comprises a FVIII protein and a first Ig constant region or a portion thereof and a second polypeptide which comprises a VWF protein comprising the D′ domain and D3 domain of VWF, a XTEN sequence having less than 288 amino acids in length, and a second Ig constant region or a portion thereof, wherein the first polypeptide and the second polypeptide are associated with each other. The invention also includes nucleotides, vectors, host cells, methods of using the chimeric proteins.