Multispecific Polypeptides Redirecting T Cells to CD123 Targets
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Solution Overview
Problem
Current bispecific antibodies for targeting CD123 in leukemia, such as MGD006, face challenges with target-independent T cell activation and require continuous intravenous infusion due to small size and lack of an Fc domain, leading to compliance issues and potential manufacturing problems.
Innovation Solution
Development of multispecific polypeptides comprising immunoglobulin single variable domains that specifically bind to the T cell receptor (TCR) and CD123, designed to redirect T cells to CD123-expressing cells with minimal target-independent activation, using specific combinations of framework regions and complementarity determining regions to enhance affinity and specificity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current bisspecific antibodies (e.g., MGD006) are used to target CD123 in leukemia, then T cell recruitment to target cells is achieved, but target-independent T cell activation occurs and continuous intravenous infusion is required
Solution Approach 1:
The patent divides the antibody structure into separate single variable domains (Fv fragments) rather than using complete antibodies. This segmentation into minimal functional units (Fv fragments with specific CDR regions) allows for reduced size while maintaining binding specificity, and enables the construction of multispecific molecules that recruit T cells to CD123+ targets without causing target-independent activation
Solution Approach 2:
The patent modifies specific local regions of the antibody - specifically optimizing the complementarity determining regions (CDRs) while maintaining framework regions. By locally optimizing the CDR3 region of the anti-CD123 binding domain and the CDR regions of the anti-TCR binding domain, the patent achieves high affinity and specificity for the intended targets while avoiding off-target effects that cause target-independent activation
2Ease of manufacture
If small size bispecific antibodies without Fc domain are used, then manufacturing complexity is reduced, but continuous intravenous infusion is required leading to compliance issues
Solution Approach 1:
The patent merges multiple Fv fragments into multispecific polypeptides that combine anti-CD123 and anti-TCR binding domains in a single molecule. This merging creates a compact structure that is easier to manufacture than full antibodies while the multspecific nature (binding both CD123 on target cells and TCR on T cells) enables prolonged residence time at the target site, effectively extending duration of action without requiring continuous infusion
3Manufacturing precision
If multisspecific polypeptides with optimized CDR regions are developed, then affinity and specificity for CD123 and TCR are enhanced, but device complexity increases
Solution Approach 1:
The patent extracts only the essential functional elements - the single variable domains (Fv fragments) with optimized CDR regions - while removing non-essential portions of the antibody structure. By taking out just the minimal required components (Fv fragments with specific CDR sequences) and eliminating the need for Fc domains or complete antibody structures, the patent achieves high binding affinity and specificity while actually reducing overall molecular complexity compared to full antibodies
Data Source
AI summary
Polypeptides are provided that bind CD123 on a target cell and the constant domain of TCR on a T cell. The polypeptides can be used in methods for treatment of CD123 associated cancers or inflammatory conditions.