Multivalent Anti-MUC1 Fab Conjugate for Cancer Imaging
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Solution Overview
Problem
Monovalent Fab fragments have a short half-life and are rapidly eliminated by renal excretion, leading to a rapid tumor-to-blood ratio that confers a signal-to-background ratio sufficient for visualizing cancer, but they lack divalent binding activity and are attenuated by labeling with detectable substances.
Innovation Solution
A conjugate comprising an anti-human MUC1 antibody Fab fragment, a peptide linker, and a ligand, which maintains excellent binding activity against human cancer-specific MUC1 even after labeling, allowing for effective visualization and treatment of cancer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If Fab fragments are used instead of full antibodies, then renal excretion and short half-life are improved for rapid tumor-to-blood ratio, but divalent binding activity is lost and binding affinity is attenuated
Solution Approach 1:
The patent combines multiple Fab fragments through disulfide bonds to create multivalent constructs that restore divalent binding activity while preserving the rapid renal excretion and short half-life characteristics of individual Fab fragments. This merging approach allows the conjugate to achieve both rapid clearance from blood and strong tumor-specific binding.
Solution Approach 2:
The invention creates composite antibody structures by linking Fab fragments via disulfide bonds and conjugating them to carrier proteins or peptides. This composite construction enables the molecule to exhibit properties of both the Fab fragment (rapid clearance, monovalent binding) and the multivalent structure (enhanced binding affinity, prolonged circulation).
2Adaptability or versatility
If Fab fragments are labeled with detectable substances for visualization, then diagnostic capability is improved, but binding activity is attenuated
Solution Approach 1:
The patent introduces disulfide bond linkers and spacer peptides as intermediary elements between the Fab fragment and detectable substances. These intermediaries maintain the spatial separation and proper orientation of the binding site, preventing steric hindrance while enabling conjugation to imaging agents or therapeutic molecules.
Solution Approach 2:
The invention extends the conjugate structure into additional spatial dimensions by attaching multiple detectable substances or therapeutic agents to the Fab fragment through linker arms. This dimensional expansion allows the binding function and detection/function delivery function to operate independently without interfering with each other.
3Reliability
If full antibodies are used, then divalent binding activity is maintained, but half-life is prolonged causing delayed tumor-to-blood ratio and liver accumulation interfering with hepatic metastasis detection
Solution Approach 1:
The patent extracts the Fc region from the full antibody structure, retaining only the Fab fragments that contain the antigen-binding sites. This extraction eliminates the Fc-mediated effects (ADCC, CDC, prolonged half-life, liver accumulation) while preserving the antigen-specific binding capability of the variable regions.
Solution Approach 2:
The invention segments the antibody molecule into separate functional domains by cleaving the Fc portion and utilizing only the Fab fragments. This segmentation allows independent optimization of each domain's function - the Fab fragments provide rapid clearance and specific binding, while the engineered disulfide linkages restore multivalent binding kinetics.
Data Source
AI summary
Provided are a conjugate comprising an anti-human MUC1 antibody Fab fragment and a peptide linker and/or a ligand, a composition for diagnosis and/or a pharmaceutical composition comprising the conjugate, a method for diagnosing and/or treating a cancer using the conjugate, and the like. In the conjugate used, the anti-human MUC1 antibody Fab fragment is bound to the ligand via the peptide linker or the like.