Sialic Acid Derivative Conjugation via NHS Ester
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Solution Overview
Problem
Current methods for attaching polysialic acid (PSA) derivatives to therapeutic agents face challenges such as low yields and instability at higher temperatures, requiring unattainable or uneconomical reactant concentrations, which affect the stability and pharmacokinetic properties of conjugated proteins.
Innovation Solution
A new process involving a preliminary step to form a terminal sialic acid unit with a primary or secondary amine group, followed by reaction with a bifunctional reagent to create a stable derivative, allowing for efficient conjugation with proteins and other biologically relevant compounds, using aprotic solvents like DMSO to minimize deactivation of NHS groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current methods are used to attach PSA derivatives to therapeutic agents, then conjugation can be achieved, but the yields are low and stability at higher temperatures is poor
Solution Approach 1:
The patent applies preliminary action by first forming a terminal sialic acid unit with a primary or secondary amine group through oxidation and reductive amination before reacting with the bifunctional reagent. This pre-preparation of reactive groups ensures stable conjugation while maintaining high yields, as the amine groups are already in place to react efficiently with the NHS ester of the bifunctional reagent.
2Reliability
If current conjugation methods are used, then PSA can be attached to therapeutic agents, but unattainable or uneconomical reactant concentrations are required
Solution Approach 1:
The patent changes the chemical parameters of the conjugation process by using a bifunctional reagent with NHS ester and amine/hydrazide groups, which enables conjugation at economically feasible reactant concentrations. The NHS ester group reacts efficiently with the pre-formed amine groups on PSA derivatives, eliminating the need for unattainable concentrations while maintaining stable conjugation.
3Productivity
If NHS groups are used in conjugation reactions, then efficient conjugation can occur, but deactivation of NHS groups occurs in protic solvents
Solution Approach 1:
The patent applies the inert environment principle by conducting the conjugation reaction in aprotic solvents such as DMSO, acetonitrile, or DMF. These aprotic solvents do not cause deactivation of the NHS groups, thereby maintaining both the efficiency and stability of the conjugation reaction. The choice of aprotic solvent creates an inert chemical environment that preserves the reactivity of the NHS ester groups.
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
This process enhances the stability and pharmacokinetic properties of PSA-derivatized proteins, offering improved circulation half-life and reduced immunogenicity, while maintaining biological activity and avoiding the toxicity concerns associated with PEGylation.
Implementation Method 1
the amine or hydrazine group of the intermediate is acylated by —CO—R1—X to form the derivative
Implementation Method 2
using aprotic solvents like DMSO to minimize deactivation of NHS groups
Data Source
AI summary
An amine or hydrazide derivative of a sialic acid unit, e.g. in a polysaccharide, is reacted with a bifunctional reagent at least one of the functionalities of which is an ester of N-hydroxy succinimide, to form an amide or hydrazide product. The product has a useful functionality, which allows it to be conjugated, for instance to proteins, drugs, drug delivery systems or the like. The process is of particular utility for derivatising amine groups introduced in sialic acid terminal groups of polysialic acids.