Zwitterionic Fluorescent Dye-Labeled VHH Domains for Low-Background Imaging
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Solution Overview
Problem
Current fluorescently labeled targeting molecules for in vivo medical imaging face challenges with unpredictable pharmacokinetic profiles due to the impact of fluorophores on molecular charge, charge distribution, and hydrophobicity, leading to non-specific uptake and background signals, which hinders accurate imaging.
Innovation Solution
Conjugates comprising immunoglobulin single variable domains labeled with specific fluorescent moieties, such as those having structures chosen from Formula I or Formula II, which exhibit optimal biodistribution profiles with exclusive renal clearance and low serum protein binding, resulting in high signal-to-background ratios and improved pharmacokinetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional fluorescent dyes (e.g., IRDye800CW) are used to label targeting molecules, then fluorescent imaging can be achieved, but non-specific uptake and background signals increase significantly
Solution Approach 1:
The patent changes the chemical structure parameters of the fluorescent dye by introducing a zwitterionic configuration with balanced surface charges. This parameter change modifies the physicochemical properties of the tracer, specifically reducing hydrophobicity and optimizing charge distribution, which directly decreases non-specific uptake and background signals while maintaining fluorescent imaging capability
Solution Approach 2:
The patent creates a composite fluorescent tracer by combining the zwitterionic dye structure with a targeting molecule (antibody, peptide, or small molecule). This composite structure integrates the fluorescent imaging function with the targeting function, while the zwitterionic character of the dye component provides reduced background interaction with serum proteins and tissues
2Measurement precision
If fluorophores with strong fluorescent properties are selected, then imaging sensitivity improves, but the impact on pharmacokinetic profile becomes unpredictable
Solution Approach 1:
The patent establishes a reliable pharmacokinetic profile by changing the charge parameters of the fluorescent dye to a zwitterionic state with balanced surface charges. This standardized parameter change across different fluorescent tracers creates predictable blood clearance and excretion pathways, making pharmacokinetic behavior consistent and reliable while maintaining high imaging sensitivity
3Reliability
If larger molecules (monoclonal antibodies) are used as targeting molecules, then target binding affinity increases, but blood clearance time and time to attain sufficient contrast increase
Solution Approach 1:
The patent segments the monoclonal antibody into smaller functional components, using only the antigen-binding variable domains (such as scFv, Fab, or nanobody fragments). This segmentation reduces the molecular size and molecular weight of the targeting molecule, enabling faster blood clearance and quicker attainment of sufficient contrast while preserving the specific target binding affinity through the intact variable domains
Solution Approach 2:
The patent extracts and removes the Fc region and other non-essential portions of the monoclonal antibody, retaining only the variable domains that provide target specificity. This extraction eliminates the portions responsible for slow clearance while maintaining the essential targeting function, achieving both high affinity binding and rapid pharmacokinetics
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 described conjugates demonstrate fast biodistribution, exclusive renal clearance, and low background signals, enabling clear visualization of tumor lesions with high specificity and depth penetration, thus enhancing the accuracy and efficiency of in vivo medical imaging.
Implementation Method 1
Fluorescence imaging is a relatively cheap, safe and high throughput in vivo imaging technology that relies on the sensitive detection of fluorescent signals emitted after excitation of a fluorescent contrast agent
Implementation Method 2
The inventors found that the conjugate according to claim 1 has an optimal biodistribution profile when administered in vivo, showing exclusive renal clearance
Data Source
AI summary
The current invention relates to a conjugate comprising an immunoglobulin single variable domain conjugated to one or more detectable labels, wherein at least one of said labels comprises a fluorescent moiety, said fluorescent moiety having a structure chosen from formula (I) or formula (II). The current invention also relates to a conjugate comprising an immunoglobulin single variable domain conjugated to one or more detectable labels, wherein said conjugate exhibits less than 10 percent serum protein binding as measured by HPLC. The invention further relates to a pharmaceutical composition comprising aforementioned conjugate and the use of aforementioned conjugate or composition.