Low-Affinity EpCAM CAR-T Cells for Selective Tumor Killing
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Solution Overview
Problem
Conventional CAR-T cell therapy for cancer faces challenges in on-target/off-tumor cytotoxicity due to high-affinity targeting of tumor antigens expressed in both cancer and normal tissues, leading to unwanted toxicity and T cell exhaustion.
Innovation Solution
Development of affinity-tuned chimeric antigen receptors (CARs) with low-affinity EpCAM single-chain variable fragments (scFv) to selectively target tumor cells while sparing normal cells, utilizing specific amino acid substitutions in the CDR-H3 region to fine-tune the binding affinity, thereby reducing cytotoxicity to normal tissues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-affinity CAR molecules are used to target tumor antigens, then tumor cell killing efficiency is improved, but on-target/off-tumor toxicity increases
Solution Approach 1:
The patent applies parameter changes by systematically varying the affinity parameter of the CAR molecule through amino acid substitutions in the CDR-H3 region. This creates a spectrum of CAR variants with different binding strengths to EpCAM, allowing optimization of the balance between tumor killing efficiency and toxicity to normal tissues expressing low levels of the antigen.
Solution Approach 2:
The patent employs partial action by using low-affinity CAR molecules that bind weakly to EpCAM. This partial binding is sufficient to recognize and target tumor cells with high EpCAM expression while being too weak to effectively bind to normal tissues with low EpCAM expression, thereby achieving selective toxicity without excessive off-target effects.
2Measurement precision
If high-affinity CAR molecules are used, then sensitivity to target antigen is improved, but selectivity for high-expression tumors deteriorates
Solution Approach 1:
The patent changes the affinity parameter of the CAR molecule by introducing specific amino acid substitutions in the CDR-H3 region. This creates a gradient of binding affinities that allows the system to distinguish between tumor cells with high antigen expression and normal cells with low expression, even at the single-cell level.
Solution Approach 2:
The patent uses low-affinity CAR molecules that provide just enough binding strength to detect and respond to high antigen density on tumor cells, while falling below the threshold for activating against low antigen density on normal cells. This partial activation threshold approach enables clear discrimination between target and non-target cells.
3Productivity
If conventional high-affinity CARs are used, then tumor targeting is improved, but T cell exhaustion increases
Solution Approach 1:
The patent changes the affinity parameter of the CAR to a lower value, which reduces the intensity of continuous signaling to the T cell. This diminished signaling level prevents over-activation and exhaustion of the T cell, allowing it to maintain functionality and persistence over extended periods while still effectively targeting tumors.
Solution Approach 2:
The patent employs partial action by using low-affinity CARs that provide moderate, sustained signaling rather than strong, continuous signaling. This partial activation maintains T cell health and longevity by avoiding the excessive signaling that leads to exhaustion, while still achieving effective tumor targeting through accumulation of weaker signals over time.
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 low-affinity EpCAM CAR-T cells effectively kill cancer cells with high EpCAM expression while minimizing toxicity to normal cells, maintaining long-term efficacy and reducing T cell exhaustion, thus enhancing the therapeutic index of CAR-T cell therapy.
Implementation Method 1
CAR molecules with high affinity to such antigens can lead to collateral targeting of healthy tissues resulting in on-target, off-tumor toxicity
Implementation Method 2
The recognition of antigen both on normal, non-target cells as well as on cancer cells can lead to both unwanted toxicity and T cell exhaustion
Data Source
AI summary
The present invention provides EpCAM antibodies with different affinities. The present invention also provides chimeric antigen receptors (CARs) specific to EpCAM. CAR T cells comprising human EpCAM scFv having a low and sufficient affinity to EpCAM can avoid targeting healthy tissues with low EpCAM expression while exhibiting long-term efficacy against tumor tissues with high EpCAM expression. The present invention also relates to an adoptive cell therapy method for treating cancer by administering the CAR-T cells comprising human EpCAM scFv to a subject suffering from cancer, whereby the CAR T cells bind to the cancer cells overexpressing EpCAM and kill the cancer cells.