CTLA-4 Binding Molecules with Shiga Toxin Scaffolds
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Solution Overview
Problem
Current cancer therapies, particularly immune checkpoint inhibitors, are not always effective and come with severe side effects, and they primarily inhibit rather than eliminate immunosuppressive immune cells in the tumor microenvironment, necessitating a more effective and less side-effect-intensive treatment option.
Innovation Solution
Development of a CTLA-4 binding molecule comprising a Shiga toxin A subunit effector polypeptide and a binding region with a VHH domain, specifically designed to target and deplete immunosuppressive immune cells by binding to CTLA-4 on their surface, potentially used in combination with other anti-cancer agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If immune checkpoint inhibitors are used to interrupt co-inhibitory signaling pathways, then antitumor immune responses are reinvigorated, but the therapy is not always effective and is associated with severe side effects
Solution Approach 1:
The patent extracts the essential binding function from full antibodies and implements it using smaller VHH domains (nanobodies). These VHH domains specifically bind to CTLA-4 on immunosuppressive immune cells, enabling targeted depletion without the severe side effects associated with conventional checkpoint inhibitors. The extraction of only the necessary binding region reduces off-target effects while maintaining therapeutic efficacy.
Solution Approach 2:
The patent changes the molecular parameters by using VHH domains instead of full antibodies. This parameter change results in smaller molecular size, altered pharmacokinetics, and different tissue penetration characteristics. The VHH domains can more effectively target and deplete immunosuppressive cells in the tumor microenvironment while reducing the immunogenicity and side effects associated with larger antibody molecules.
2Reliability
If immune checkpoint inhibitors are used to inhibit immunosuppressive immune cells, then tumor growth is slowed, but the cells are not eliminated from the tumor microenvironment
Solution Approach 1:
The patent utilizes the natural immunosuppressive function of CTLA-4 as a target marker. By designing VHH domains that specifically bind to CTLA-4 on immunosuppressive immune cells (Tregs, MDSCs, TAMs), the therapy converts the presence of these harmful cells into a beneficial targeting opportunity. The VHH domains deliver cytotoxic payloads specifically to CTLA-4+ cells, eliminating the very cells that cause immunosuppression while sparing other immune cells.
3Reliability
If conventional antibody-based therapies are used to target CTLA-4, then binding affinity is achieved, but molecular size and complexity increase
Solution Approach 1:
The patent extracts only the variable heavy domain (VHH) from complete antibodies, creating minimal functional units that retain CTLA-4 binding capability. These VHH domains consist of approximately 15 kDa molecular weight compared to the 150 kDa or larger full antibodies. The extraction eliminates unnecessary constant regions and light chains, reducing molecular complexity while preserving the essential antigen-binding function through optimized CDR regions.
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 CTLA-4 binding molecule effectively depletes immunosuppressive immune cells and can directly kill tumor cells, enhancing cancer therapy efficacy by lifting immunosuppression in the tumor microenvironment, thereby improving treatment outcomes with reduced side effects.
Implementation Method 1
comprising (i) a Shiga toxin A subunit effector polypeptide and (ii) a binding region capable of specifically binding an extracellular part of CTLA-4
Data Source
AI summary
Provided herein are binding molecules that each comprise (1) a Shiga toxin A subunit effector polypeptide and (2) a binding region capable of specifically binding CTLA-4 on the surface of cell, such as a tumor cell or an immunosuppressive immune cell. Further provided are methods of using such binding molecules to treat diseases and disorders, such as cancer.