Expression-Enhancing Locus for Stable Bispecific Antibody Production
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Solution Overview
Problem
Existing mammalian expression systems face challenges in achieving stable and efficient expression of multispecific antigen-binding proteins, particularly bispecific antibodies, due to variations in expression levels and instability of integrated genes, often favoring homodimer production over desired heterodimers or multimers.
Innovation Solution
Integration of exogenous nucleic acid sequences encoding bispecific antigen-binding proteins at a specific site within an enhanced expression locus, utilizing vectors with recombinase recognition sites and transcriptional regulatory sequences, allowing for site-specific integration and stable expression of multiple chains, including different CH3 domains and variable regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If exogenous nucleic acid sequences are integrated into mammalian expression systems, then expression of recombinant proteins is achieved, but expression stability and consistency deteriorate due to position effects and local genetic environment variations
Solution Approach 1:
The patent creates a predetermined safe harbor locus in the CHO cell genome with optimized genetic architecture including strong promoters (EF1α, PHO), polyadenylation signals, and selection markers positioned in advance. This pre-engineered locus ensures that when exogenous nucleic acid sequences encoding multispecific antibodies are integrated, they automatically benefit from a stable and high-expression environment, eliminating the randomness of position effects.
2Adaptability or versatility
If multiple genes are integrated for expression of multisspecific antibodies, then heterodimer or multimer production is enabled, but expression variation increases and instability occurs
Solution Approach 1:
The patent combines multiple gene expression cassettes (encoding different antibody chains with distinct CH3 domains and variable regions) into a single integrated locus. This merging approach ensures all chains are expressed from the same genomic location under coordinated control, eliminating inter-gene positional variations and ensuring consistent heterodimer formation.
Solution Approach 2:
The patent creates a specialized local genetic environment at the safe harbor locus with enhanced features: strong constitutive promoters for each chain, optimized Kozak sequences, proper splicing signals, and polyadenylation sites. This localized optimization ensures each integrated gene achieves high and consistent expression regardless of its position within the locus.
3Ease of manufacture
If random integration is used for gene transfer, then ease of manufacture is improved, but expression levels vary widely due to position effects
Solution Approach 1:
The patent employs homologous recombination as an intermediary mechanism between the exogenous nucleic acid sequences and the safe harbor locus. By designing integration vectors with homology arms matching the predetermined locus, the system achieves site-specific integration through homologous recombination, which is more precise than random integration but maintains relative ease of manufacture through standard molecular biology techniques.
Data Source
AI summary
This invention relates to site-specific integration and expression of recombinant proteins in eukaryotic cells. In particular, the invention includes compositions and methods for improved expression of antibodies including bispecific antibodies in eukaryotic cells, particularly Chinese hamster (Cricetulus griseus) cell lines, by employing an expression-enhancing locus.