Uncleaved Pel B Leader scFv Fusion Protein for CEA Targeting
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Solution Overview
Problem
Conventional cancer therapies face challenges due to poor selectivity, leading to non-specific targeting of tumors, which limits the escalation of therapeutic doses and increases toxicity to normal tissues. Existing antibody-based treatments, such as those targeting carcinoembryonic antigen (CEA) and its related molecules, face limitations like rapid blood clearance and immune responses.
Innovation Solution
Development of a fusion protein, DIATHIS-1, comprising a single-chain variable fragment (scFv) specific for CEA and CEACAM1, incorporating an uncleaved Pel B leader sequence that encourages oligomer formation, enhancing stability and affinity, and is engineered for improved pharmacokinetics and tumor targeting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pharmacological approaches are used for cancer therapy, then treatment can be administered, but selectivity is poor leading to toxicity to normal tissues
Solution Approach 1:
The patent segments the antibody into a single-chain variable fragment (scFv) format, separating the antigen-binding function from the full-length antibody structure. This segmentation enables better tumor penetration while maintaining selectivity, directly addressing the contradiction between achieving reliable targeting and reducing toxicity to normal tissues.
Solution Approach 2:
The patent modifies the scFv molecule by engineering a C-terminal cysteine residue to enable disulphide bridging and formation of (scFv)2 fragments. This parameter change in molecular structure slows down blood clearance and enhances selectivity, allowing for better tumor targeting while reducing off-target effects.
2Speed
If scFv is used instead of full length monoclonal antibody, then tumor penetration is improved, but blood clearance is rapid
Solution Approach 1:
The patent merges two scFv fragments through disulphide bridging to form (scFv)2 bivalent molecules. This merging increases molecular weight and slows renal clearance, extending blood half-life while preserving the enhanced tumor penetration capability of the scFv format.
Solution Approach 2:
The patent creates a composite molecular structure by incorporating a C-terminal cysteine residue that forms disulphide bonds between scFv chains. This composite (scFv)2 structure combines the advantages of small size for penetration with increased stability and prolonged circulation time.
3Quantity of substance
If murine hybridoma technology is used to produce monoclonal antibodies, then numerous well characterised mAbs are available, but human anti-mouse antibody response occurs
Solution Approach 1:
The patent uses phage antibody technology to copy and display human antibody fragments on filamentous bacteriophage. This allows isolation of human scFv sequences that can be produced in bacterial systems, providing humanized alternatives to murine mAbs that avoid HAMA responses while maintaining the availability of numerous well-characterized antibodies.
Data Source
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AI summary
An anti-CEA scFv having an uncleaved Pel B leader sequence is surprisingly stable and is highly specific for CEA and CEACAMl.