5′-Phosphoramidate Oligonucleotide Stabilization

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Solution Overview

Problem

Current 5′-phosphate stabilizing modifications for siRNAs, such as 5′-(E)-vinylphosphonate, are costly and have complex synthesis pathways, limiting their therapeutic application and duration of effect in vivo.

Innovation Solution

Development of modified oligonucleotides with specific intersubunit linkages, including chlorophosphoramidite reactions and deprotecting agents, to enhance 5′-phosphate stability and resistance to phosphatases, thereby improving siRNA activity and duration of effect.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If 5′-(E)-vinylphosphonate modification is used to stabilize the 5′-phosphate, then resistance to phosphatases and complex stability are improved, but manufacturing cost and synthesis complexity increase

Engineering Contradiction:

Improve5′-phosphate stabilityVSAvoidsynthesis pathway complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses 5′-phosphoramidate as a simplified copy/analogue of the 5′-(E)-vinylphosphonate modification. The phosphoramidate group replicates the stabilizing function by forming electrostatic interactions with the MID domain of hAgo2, but achieves this through a more straightforward chemical synthesis pathway that avoids the complex vinylphosphonate chemistry while maintaining therapeutic efficacy

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent changes the chemical parameter of the 5′-phosphate modification from vinylphosphonate to phosphoramidate. This parameter change maintains the essential electrostatic interaction capability with hAgo2 (functional equivalence) while dramatically simplifying the synthesis pathway and reducing manufacturing costs, thus resolving the contradiction between stability and complexity

Inventive Principle:

Principle #35Parameter changes

2Reliability

If 5′-(E)-vinylphosphonate modification is used to stabilize the 5′-phosphate, then resistance to phosphatases and complex stability are improved, but manufacturing cost increases

Engineering Contradiction:

Improve5′-phosphate stabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent employs 5′-phosphoramidate as a cost-effective copy of the 5′-(E)-vinylphosphonate modification. The phosphoramidate group replicates the phosphatase resistance and hAgo2 binding capability through standard phosphoramidite chemistry, which is more economically viable than the specialized vinylphosphonate chemistry, thereby reducing manufacturing costs while preserving therapeutic stability

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent adopts 5′-phosphoramidate as a simpler, more economical modification that achieves the necessary stability without the high cost of vinylphosphonate. The phosphoramidate modification uses readily available reagents and standard oligonucleotide synthesis protocols, making it a cost-effective solution that maintains therapeutic efficacy while reducing manufacturing expenses

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If 5′-phosphate is used for RISC complex formation, then siRNA activity is improved, but susceptibility to phosphatases increases

Engineering Contradiction:

ImprovesiRNA activityVSAvoidduration of effect in vivo

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The patent applies 5′-phosphoramidate modification as a preliminary protective action before the siRNA enters the RISC complex. The phosphoramidate group pre-establishes electrostatic interactions with the MID domain of hAgo2, ensuring stable complex formation and protecting the 5′-phosphate from phosphatase attack throughout the duration of therapeutic action, thus extending in vivo persistence

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses 5′-phosphoramidate modification as a beforehand cushioning measure against phosphatase degradation. The phosphoramidate group creates a stable electrostatic interaction with hAgo2 that protects the 5′-phosphate region from enzymatic cleavage, providing advance protection that maintains siRNA activity and extends duration of effect in vivo

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 oligonucleotides provide enhanced stability and resistance to phosphatases, leading to prolonged siRNA activity and therapeutic benefits without the cost and complexity of existing methods.

Implementation Method 1

The 5′-phosphate of a guide strand is known to bind to the MID domain of human Argonaute 2 (hAgo2), a key siRNA (miRNA) RISC forming protein, by forming electrostatic interaction with proximal cationic amino acid residues in the domain

Methodology Applied

Scientific EffectElectrostatic interaction: Electrostatics