Fluorinated Sialic Acid Derivatives for Glycoprotein Stability
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Solution Overview
Problem
Current protein therapeutics face challenges with immune responses and high production costs, and their pharmacokinetic profiles are limited by rapid clearance due to enzymatic hydrolysis, particularly the removal of terminal sialic acid, which reduces their circulatory half-life.
Innovation Solution
Development of modified sialic acids, such as those with fluorine substitutions at the 7-position, which are resistant to enzymatic hydrolysis and can be efficiently incorporated into glycoproteins, thereby stabilizing the glycosidic bond and prolonging the circulatory half-life of therapeutic glycoproteins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If natural sialic acid is used in glycoprotein therapeutics, then the protein can be effectively masked from liver clearance, but the glycosidic bond is susceptible to enzymatic hydrolysis by sialidases, reducing circulatory half-life
Solution Approach 1:
The patent applies parameter changes by introducing fluorine atoms at the 7-position of the sialic acid molecule, replacing a hydrogen atom with a highly electronegative fluorine substituent. This chemical modification changes the electronic parameters of the glycosidic bond, increasing its stability against enzymatic hydrolysis while maintaining the masking function against liver clearance receptors.
Solution Approach 2:
The patent creates a composite molecular structure by combining sialic acid with fluorine substituents at the 7-position, forming a modified sialic acid derivative (e.g., 7-fluorosialic acid). This composite structure integrates the protective masking function of sialic acid with the enhanced stability provided by fluorine substitution, resolving the contradiction between resistance to hydrolysis and circulatory half-life.
2Reliability
If sialic acid is modified with fluorine substitution, then enzymatic hydrolysis resistance increases, but the complexity of synthesis and incorporation into glycoproteins increases
Solution Approach 1:
The patent applies preliminary action by pre-synthesizing the fluorinated sialic acid derivatives and their corresponding nucleotide phosphates (e.g., CMP-7-fluorosialic acid) before incorporating them into glycoproteins. This allows the stable, hydrolysis-resistant sialic acid moiety to be prepared in advance with high purity, then efficiently transferred to the protein target using sialyltransferase enzymes, thereby managing synthesis complexity through staged preparation.
Solution Approach 2:
The patent uses nucleotide phosphates (such as CMP-7-fluorosialic acid) as intermediary carriers that facilitate the transfer of the fluorinated sialic acid to the glycoprotein. This intermediary approach simplifies the overall process by allowing the unstable, hard-to-handle fluorinated sialic acid to be transported and installed through a controlled enzymatic transfer mechanism, reducing the complexity of direct incorporation.
3Productivity
If conventional sialic acid is used, then the glycoprotein can be efficiently produced and incorporated, but rapid clearance from circulation occurs due to recognition by asialo-receptors in the liver
Solution Approach 1:
The patent changes the chemical parameters of sialic acid by introducing fluorine at the 7-position, which modifies the molecular recognition properties. This parameter change maintains efficient production and incorporation through sialyltransferase enzymes while simultaneously preventing recognition by asialo-receptors in the liver, thereby extending circulatory half-life without sacrificing production efficiency.
Solution Approach 2:
The patent applies local quality by making a specific localized modification at the 7-position of the sialic acid molecule while maintaining the rest of the sialic acid structure intact. This localized fluorine substitution preserves the essential functions of sialic acid (masking galactose, maintaining transferase recognition) while adding the specific property of enhanced stability and extended circulatory half-life.
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 modified sialic acids significantly reduce the rate of enzymatic hydrolysis, leading to improved pharmacokinetic properties and extended serum half-lives of glycoproteins, enhancing the therapeutic efficacy by maintaining stability and bioavailability.
Implementation Method 1
This is likely due to the close proximity of the highly electronegative fluorine atom to the anomeric carbon thereby inductively destabilizing any oxocarbenium ion-like transition state and greatly increasing the activation energy for bond cleavage.
Implementation Method 2
Replacement of the normal oxygen linkage with a sulfur rendered these S-linked sialosides far more resistant to chemical or enzymatic hydrolysis compared with their O-linked homologues.
Implementation Method 3
Sialic acid is commonly found linked to galactose and so its presence on the glycan terminus effectively acts as a mask for the galactose, blocking the binding of the glycoprotein to the asialo-receptors in the liver and reducing the clearance rate.
Implementation Method 4
The action of any mammalian sialidases (sialic acid hydrolysing enzymes) on a glycoprotein is to remove the terminal sialic acid to expose the terminal galactose.
Data Source
AI summary
This invention provides compound having a structure of Formulas: Furthermore, methods and uses of such compounds for covalently bonding to a sugar acceptor, to form modified protein therapeutics having reduced enzymatic hydrolysis, improved biological stability or an improved pharmacokinetic property.