VHH Site-Specific Conjugation Using ETAC for Stable Monolabeling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for site-specific conjugation of antibody fragments like VHHs are prone to protein aggregation and instability under physiological conditions, and maleimide-based conjugation leads to non-functional and potentially blocking epitopes.
Innovation Solution
A method using the ETAC-biotin linker to monolabel single VHH units by targeting a cysteine-histidine motif, followed by selective enrichment of single-site conjugates via a nucleophilic agent like TCEP to remove multi-label targets, ensuring stability and functional integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If maleimide-based conjugation is used to modify free cysteines, then site-specific conjugation is achieved, but the conjugation becomes unstable under physiologically reducing conditions leading to retro-Michael addition
Solution Approach 1:
The patent changes the chemical parameters of the conjugation system by replacing maleimide with ETAC reagent, which has different reactivity characteristics. The ETAC reagent forms stable thioether bonds that are resistant to retro-Michael addition under reducing conditions, while maintaining site-specific conjugation at the engineered cysteine residue.
Solution Approach 2:
The patent uses a disposable engineered cysteine residue that is specifically designed for conjugation and then sacrificed or masked after the reaction. This allows for clean, site-specific conjugation without the need for reversible or stable long-term conjugation that would be susceptible to retro-Michael addition.
2Manufacturing precision
If engineered cysteines are incorporated for site-specific conjugation, then conjugation specificity is improved, but free cysteines can form disulfide bonds leading to protein aggregation
Solution Approach 1:
The patent performs preliminary reduction of disulfide bonds using TCEP before conjugation, and maintains reducing conditions throughout the process. This preliminary action prevents disulfide bond formation and subsequent aggregation, allowing the engineered cysteines to remain available for specific ETAC conjugation without side reactions.
Solution Approach 2:
The patent introduces TCEP as an intermediary reducing agent that mediates between the engineered cysteines and the conjugation process. TCEP prevents disulfide bond formation by maintaining cysteines in their reduced, nucleophilic state, thereby preventing aggregation while enabling specific conjugation.
3Productivity
If multiple ETAC-biotin linkers are provided in excess, then multiple Michael acceptors within VHH are reacted, but multi-label targets are formed that need to be removed
Solution Approach 1:
The patent changes the chemical environment by adding excess TCEP after conjugation, which selectively removes multi-label products through retro-Michael addition. This parameter change allows differentiation between single-site and multi-site conjugates based on their stability to reducing conditions.
Solution Approach 2:
The patent uses a feedback mechanism where the presence of multi-label products triggers the addition of excess TCEP, which selectively removes them. This feedback loop ensures that only single-site conjugates remain in the final product, achieving high purity without compromising initial conjugation efficiency.
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 method achieves stable, site-specific conjugation of VHHs that maintain functional binding to tumor antigens and induce tumor cell lysis, enhancing the efficacy of biotin-specific adapter CAR T cells.
Implementation Method 1
initiating Michael addition between a first and a second amino acid by providing a reagent according to formula (I)
Implementation Method 2
Adding a nucleophilic agent to remove the Michael addition products between two second amino acid by retro-Michael addition
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention is directed to a method for providing a polypetide with a detectable label, wherein the polypetide comprises at least 5 amino acids of which a first amino acid is C (Cysteine) and at least one second amino acid is selected from the group consisting of S (Serine), T (Threonine), Y (Tyrosine), K (Lysine), H (Histidine) and R (Arginine) characterized by the steps a) initiating Michael addition between a first and a second amino acid by providing a reagent according to formula (I) With R1 = -Biotin, Thiamine, Peptide with 2 - 30 amino acids, oligonucleotides with 6 - 100 nucleotides, -DBCO, DBCO, -N3,N3, -Fluorophore, -Fluorescent protein R2 = substituted or unsubstituted aromatic residues R3 = H, F, NO2, alkyl with 1 to 5 carbon atoms R4 = direct bond, substituted or unsubstituted alkyl, amine or amide residue with 1 to 20 carbon atoms b) Adding a nucleophilic agent to remove the Michael addition products between two second amino acid by retro-Michael addition.