CD206-Targeting Peptide Cyclization for Affinity and Stability
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Solution Overview
Problem
Existing short linear targeting peptides for CD206 macrophages have low affinity and stability, limiting their therapeutic and diagnostic applications, and are restricted to intravenous administration, necessitating a need for higher affinity, stability, and alternative administration routes.
Innovation Solution
Engineering a CD206-binding peptide (mUNO) with a disulfide bond and cyclization loop, derived from SFTI-1, to enhance affinity and stability, allowing oral delivery and targeting CD206+ macrophages, and conjugating it with therapeutic or detectable agents for targeted therapy and diagnosis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If short linear targeting peptides are used to target CD206 macrophages, then the peptide can guide therapeutic or imaging cargos to tumors, but the affinity is low and proteolytic degradation occurs
Solution Approach 1:
The peptide structure was modified by introducing a disulfide bond to constrain conformation and by cyclizing the peptide backbone. These structural parameter changes reduced conformational freedom, increased proteolytic stability, and enhanced binding affinity to CD206 macrophages while maintaining targeting functionality
Solution Approach 2:
The targeting peptide was conjugated with therapeutic agents (such as verteporfin for photodynamic therapy) or imaging agents to create composite conjugates. This composite approach combines the targeting capability of the stabilized peptide with the therapeutic or diagnostic functionality of the conjugated agent, enabling dual functionality in a single molecule
2Ease of manufacture
If unconstrained short peptides are used, then the peptide structure is simple and easy to synthesize, but conformational freedom leads to poor affinity and proteolytic degradation
Solution Approach 1:
The peptide was cyclized to reduce conformational freedom and improve binding affinity. The cyclization was achieved through forming a disulfide bond between cysteine residues, which constrained the peptide into a specific conformation that enhanced CD206 binding while remaining compatible with standard peptide synthesis methods
Solution Approach 2:
The disulfide bond was strategically positioned within the peptide sequence to constrain only the critical binding region, allowing the rest of the peptide to maintain flexibility for binding while protecting against proteolytic degradation. This localized constraint approach maintained synthesis simplicity while improving affinity
3Reliability
If intravenous administration is used for therapeutic peptides, then the peptide can reach the target, but the administration route is invasive and limited
Solution Approach 1:
The peptide's proteolytic stability was enhanced through disulfide bond formation and cyclization, which protected the peptide from degradation in the gastrointestinal tract. This stability improvement enabled oral administration, transforming the delivery parameter from parenteral (invasive) to gastrointestinal (non-invasive) route while maintaining delivery reliability to tumor-associated macrophages
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 engineered peptide achieves 15-fold higher affinity and 5-fold higher stability, enabling effective targeting and modulation of CD206+ macrophages, reducing tumor progression, and providing diagnostic and therapeutic benefits, including anti-leishmanial activity.
Implementation Method 1
the present inventors exploited the bounties of the Sunflower Trypsin Inhibitor I peptide (SFTI-1, SEQ ID NO: 4: GRCTKSIPPICFPD), a plant-derived peptide, composed of two loops separated by a disulfide bond
Implementation Method 2
The macrophage mannose receptor 1 (CD206, encoded by the gene MRC1), is over-expressed on anti-inflammatory macrophages and protumoral and pro-metastatic subpopulation of TAMs. Targeting CD206 has applications in cancer therapy
Implementation Method 3
By secreting cytokines that skew macrophages to M2, tumors can expand this CD206+ TAM compartment
Implementation Method 4
The present inventors also reported a Verteporfin conjugate of this engineered CD206-binding peptide that can be used for light-dependent depletion of CD206+ macrophages
Data Source
Figure 1A
Figure 1B~1D
Figure 2A~2B
AI summary
The invention relates to a peptide that targets macrophages, conjugates comprising said peptide, and therapeutic and diagnostic uses thereof. More particularly, the present invention refers to a peptide that targets CD206 which is expressed in M2-macrophages.