HER2-binding polypeptide rapid blood clearance
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Solution Overview
Problem
Current methods for determining HER2 expression status in cancer, such as biopsy analysis, are invasive and complicated, while radionuclide molecular imaging using therapeutic antibodies faces challenges like slow blood clearance leading to low imaging contrast and elevated dose burdens.
Innovation Solution
Development of a HER2-binding polypeptide with a specific amino acid sequence that allows for efficient binding to HER2, minimal non-specific binding, and the ability to be labeled with radionuclides without additional chelating groups, thereby improving imaging contrast and reducing dose burdens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If therapeutic antibodies are used for radionuclide molecular imaging, then HER2 detection capability is achieved, but blood clearance is slow leading to low imaging contrast and elevated dose burden
Solution Approach 1:
The patent extracts the essential binding function from the complete antibody molecule by using only the Z variant scaffold (residues 3-60 of Protein A domain B), which retains HER2 binding capability while removing the Fc region that causes slow clearance. This extraction of the functional core resolves the contradiction between detection capability and clearance speed.
Solution Approach 2:
The Z variant polypeptide serves as a short-lived, rapidly cleared imaging probe that performs its detection function quickly and then is rapidly eliminated from the bloodstream. This disposable-like behavior enables repeated imaging studies with minimal cumulative radiation dose, resolving the contradiction between detection effectiveness and dose burden.
2Productivity
If Z variant scaffold is re-engineered to improve synthesis yield and storage stability, then peptide synthesis efficiency is improved, but renal uptake increases which is undesirable for imaging
Solution Approach 1:
The patent applies local quality changes by making specific, targeted amino acid substitutions at particular positions in the Z variant sequence (e.g., positions 10, 12, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58) to improve synthesis yield and stability while carefully controlling the hydrophobicity and charge distribution to minimize renal uptake. This localized optimization resolves the contradiction between productivity and harmful renal accumulation.
Solution Approach 2:
The patent systematically changes amino acid parameters (hydrophobicity, charge, steric properties) at specific positions to optimize the balance between synthesis stability and biodistribution. By adjusting these molecular parameters, the patent achieves high synthesis yield and storage stability while maintaining favorable renal clearance characteristics.
3Ease of operation
If amino acid substitutions are made to eliminate binding to IgG and IgM, then blood clearance is facilitated, but imaging contrast may be affected
Solution Approach 1:
The patent uses the Z variant scaffold as an intermediary structure that mediates between the need for rapid blood clearance (achieved by eliminating IgG/IgM binding through specific amino acid substitutions) and the need for high imaging contrast (maintained through optimized HER2 binding affinity). The scaffold acts as a bridge that decouples clearance properties from binding properties, allowing independent optimization of both characteristics.
Data Source
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AI summary
A HER2-binding polypeptide is provided, comprising the amino acid sequence SEQ ID NO:1. Also provided is a radiolabeled polypeptide consisting of a radiochelate of the HER2-binding polypeptide and a radionuclide. Also provided are methods and uses employing the polypeptide in therapeutic, diagnostic and prognostic applications, e.g. relating to cancers characterized by overexpression of HER2.