Truncated EGFRt Epitope for High-Purity T Cell Selection
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Solution Overview
Problem
Existing immunotherapy strategies face challenges due to immunologic rejection of genetically modified immune cells expressing antibiotic selection proteins, leading to product-to-product variability in transgene expression and inefficiencies in cell purification.
Innovation Solution
Development of a non-immunogenic selection epitope, such as a truncated epidermal growth factor receptor (EGFRt), which retains an extracellular epitope recognized by a known antibody like cetuximab, allowing for immunomagnetic selection and enrichment of genetically modified T cells without inducing immune rejection, and serving as a tracking and suicide gene.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If antibiotic selection proteins are used in transduction strategy, then selection of transduced cells is achieved, but immunologic rejection of cell products occurs
Solution Approach 1:
The patent changes the selection marker from antibiotic resistance proteins to a truncated endogenous cell-surface molecule (e.g., truncated EGFR) that retains antibody binding capability but lacks immunogenicity. This parameter change in the selection marker type eliminates immunologic rejection while maintaining selection efficiency through immunomagnetic purification.
Solution Approach 2:
The patent extracts only the essential epitope portion of the endogenous cell-surface molecule that is recognized by antibodies, while removing the immunogenic portions and signaling domains. This extraction creates a truncated version that maintains antibody binding for selection but eliminates the harmful immunologic response.
2Reliability
If full-length endogenous cell-surface molecules are used for selection, then antibody recognition is achieved, but signaling or trafficking functions cause unwanted effects
Solution Approach 1:
The patent extracts only the extracellular epitope domain of the endogenous cell-surface molecule that is recognized by antibodies, while removing the transmembrane and intracellular signaling/trafficking domains. This creates a truncated molecule that maintains antibody binding capability but eliminates unwanted signaling or trafficking functions.
Solution Approach 2:
The patent segments the endogenous cell-surface molecule into functional domains, retaining only the antibody-binding epitope portion while separating and removing the signaling and trafficking domains. This segmentation allows independent optimization of antibody recognition without harmful downstream effects.
3Ease of manufacture
If conventional transduction methods are used, then genetic modification is achieved, but product-to-product variability in transgene expression occurs
Solution Approach 1:
The patent implements a feedback mechanism where the truncated endogenous molecule serves as a selectable marker that provides immediate visual and functional feedback for successful transduction. This enables precise identification and selection of uniformly transduced cells through immunomagnetic purification, eliminating product variability.
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
The EGFRt enables high-purity enrichment of T cells (up to 99%) with maintained effector function, serving as a reliable selection marker and tracking tool, and providing a suicide gene mechanism through ADCC pathways, thus enhancing the efficacy of immunotherapy.
Implementation Method 1
retains an extracellular epitope recognized by a known antibody like cetuximab
Implementation Method 2
allowing for immunomagnetic selection and enrichment of genetically modified T cells
Implementation Method 3
providing a suicide gene mechanism through ADCC pathways
Data Source
AI summary
A non-immunogenic selection epitope may be generated by removing certain amino acid sequences of the protein. For example, a gene encoding a truncated human epidermal growth factor receptor polypeptide (EGFRt) that lacks the membrane distal EGF-binding domain and the cytoplasmic signaling tail, but retains an extracellular epitope recognized by an anti-EGFR antibody is provided. Cells may be genetically modified to express EGFRt and then purified without the immunoactivity that would accompany the use of full-length EGFR immunoactivity. Through flow cytometric analysis, EGFRt was successfully utilized as an in vivo tracking marker for genetically modified human T cell engraftment in mice. Furthermore, EGFRt was demonstrated to have cellular depletion potential through cetuximab mediated antibody dependent cellular cytotoxicity (ADCC) pathways. Thus, EGFRt may be used as a non-immunogenic selection tool, tracking marker, a depletion tool or a suicide gene for genetically modified cells having therapeutic potential.