CD3ε Binding Protein Domains for Lower-Toxicity T-Cell Engagement
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Solution Overview
Problem
Existing bispecific antibodies for recruiting cytolytic T cells to kill tumor cells face challenges such as unfavorable toxicity, potential immunogenicity, and manufacturing issues, limiting their clinical use.
Innovation Solution
Development of novel CD3ε specific binding proteins with high affinity for tumor antigens and weak affinity for T cells, featuring high thermostability, reduced deamidation risk, and decreased immunogenicity, including specific antigen binding domains and conjugation to half-life extending moieties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bispecific antibodies are used to recruit cytolytic T cells to kill tumor cells, then T cell recruitment and tumor cell killing is achieved, but toxicity and immunogenicity increase
Solution Approach 1:
The patent segments the antibody structure into distinct domains with specialized functions: the VH323 domain specifically binds CD3ε on T cells with controlled affinity, while the VL domain binds tumor-associated antigens. This segmentation allows independent optimization of each binding interface to achieve selective tumor cell killing while minimizing off-target toxicity and immunogenicity.
Solution Approach 2:
The patent applies local quality by engineering specific affinity characteristics at different binding sites. The VH323 domain is designed with optimal affinity for CD3ε to ensure sufficient T cell recruitment, while the overall bispecific antibody structure is configured to limit excessive T cell activation that would cause toxicity. This localized control of binding strength at different sites resolves the contradiction between efficacy and safety.
2Reliability
If high potency bsTCE is used to achieve tumor cell killing, then therapeutic efficacy is improved, but formulation and dosing challenges increase
Solution Approach 1:
The patent utilizes parameter changes by systematically optimizing the affinity of the VH323 domain for CD3ε and the VL domain for tumor antigens. By adjusting binding parameters within optimal ranges rather than maximizing affinity at all sites, the antibody achieves therapeutic efficacy while maintaining favorable pharmacokinetic properties that simplify formulation and dosing. The controlled affinity parameters prevent excessive potency that would create manufacturing challenges.
3Speed
If bsTCE with high affinity for CD3 is used to activate T cells, then T cell activation is enhanced, but rapid and severe toxicity occurs
Solution Approach 1:
The patent applies partial action by using the VH323 domain to bind CD3ε with optimized rather than maximal affinity. This partial binding strength is sufficient to activate T cells and enable tumor cell killing, but does not excessively activate T cells to the point of causing rapid and severe toxicity. The controlled partial activation resolves the contradiction between activation speed and toxicity.
Solution Approach 2:
The bisspecific antibody structure acts as an intermediary that mediates T cell activation through CD3ε binding while simultaneously directing the activated T cells to tumor cells via the VL domain. This intermediary function controls the activation process to be sufficient for efficacy but limited enough to avoid severe toxicity, bridging the gap between T cell activation and selective tumor targeting.
Data Source
AI summary
The disclosure provides antigen binding domains that bind cluster of differentiation 3 (CD3) protein, comprising the antigen binding domains that bind CD3ε, polynucleotides encoding them, vectors, host cells, methods of making and using them.