Fab CAR Synapse Optimization for Bulky Antigens
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Solution Overview
Problem
Chimeric antigen receptors (CARs) face challenges in effectively targeting and killing cancer cells with bulky extracellular domains due to suboptimal synapse formation, which leads to inhibited tyrosine phosphorylation and kinase activity, limiting their signaling efficiency.
Innovation Solution
The development of CARs with a Fab antigen binding domain, which improves the targeting and killing of bulky antigens by optimizing the synaptic distance and excluding phosphatases like CD45 and CD148, enhancing CAR-mediated signaling and cell killing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a classical CAR with scFv antigen binding domain is used, then the structure is simple and easy to manufacture, but it fails to signal efficiently in response to antigens with bulky extracellular domains due to suboptimal synapse formation
Solution Approach 1:
The patent changes the physical parameters of the CAR extracellular domain by replacing scFv with Fab, which has different dimensional characteristics. This parameter change optimizes the synaptic distance for bulky antigens while maintaining manufacturability through established antibody production methods
Solution Approach 2:
The Fab antigen binding domain is segmented into heavy chain variable region (VH) and light chain variable region (VL) domains, allowing independent optimization of each domain's contribution to antigen binding and synapse formation, thereby improving signaling efficiency for bulky targets
2Length of moving object
If the CAR targets a membrane distal epitope on bulky antigens like CD22, then the synapse length becomes suboptimal allowing phosphatases to enter and inhibit signaling, but if the CAR targets membrane proximal regions, then steric occlusion prevents optimal ligation
Solution Approach 1:
The patent optimizes the length parameter of the CAR extracellular domain by using Fab instead of scFv, creating an optimal synaptic distance that excludes phosphatases while maintaining access to membrane distal epitopes on bulky antigens like CD22
Solution Approach 2:
The Fab extracellular domain acts as an intermediary structure that mediates the interaction between the T cell and bulky antigens, positioning the antigen binding site at an optimal distance that prevents phosphatase entry while maintaining ligand access
3Reliability
If a Fab antigen binding domain is used instead of scFv, then the synaptic distance is optimized and phosphatases are excluded improving signaling, but the device complexity increases
Solution Approach 1:
The Fab domain serves multiple functions simultaneously: it provides antigen binding capability, optimizes synapse formation geometry, and excludes phosphatases through its structural properties. This multi-functionality justifies the increased complexity by delivering superior signaling efficiency for bulky antigens
Data Source
AI summary
The present invention provides a chimeric antigen receptor (CAR) which binds a target antigen having a bulky extra-cellular domain, wherein the CAR comprises a Fab antigen binding domain. The present invention also provides nucleic acid sequences and constructs encoding such a CAR, cells expressing such a CAR and their therapeutic uses.