Asymmetric siRNA with Localized Chemical Modifications
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
There is a need for self-delivering siRNA that achieves efficient RISC entry, minimizes immune response and off-target effects, facilitates cellular uptake without formulation, and ensures specific tissue distribution.
Innovation Solution
The development of siRNA compounds with specific structural properties, including full chemical stabilization, asymmetry, 11-16 base pair duplexes, an alternating pattern of chemically-modified nucleotides, and fully phosphorothioated tails, which can be conjugated to targeting agents like cholesterol for enhanced efficacy and distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional siRNA structures are used, then immune response and off-target effects are triggered, but efficacy and tissue distribution are limited
Solution Approach 1:
The patent applies local quality by implementing asymmetric chemical modifications where specific nucleotides at defined positions (e.g., positions 2 and 14 from the 5' end are not 2'-methoxy-ribonucleotides) receive different modifications than others. This localized differentiation of modification patterns allows the siRNA to achieve enhanced stability and reduced immune response at specific locations while maintaining overall functionality.
Solution Approach 2:
The patent employs asymmetry through its core structural design where the sense and antisense strands have non-equivalent modification patterns. The asymmetric arrangement of phosphorothioate linkages (positions 1-6 or 1-7 from the 3' end) and the specific exclusion of 2'-methoxy modifications at positions 2 and 14 creates an inherently unbalanced structure that optimizes both efficacy and reduces harmful effects.
2Stability of the object's composition
If fully chemically-modified ribonucleotides are used, then nuclease resistance is increased, but cellular uptake and tissue distribution are improved
Solution Approach 1:
The patent applies parameter changes by systematically varying the chemical modification pattern across different nucleotide positions. Specifically, it uses a combination of 2'-fluoro and 2'-methoxy modifications at different locations, along with phosphorothioate linkages at defined positions, to create an optimized balance between stability and biological activity. This multi-parameter optimization enables the siRNA to resist nucleases while maintaining enhanced cellular uptake and tissue distribution.
Data Source
AI summary
Provided herein are self-delivering oligonucleotides that are characterized by efficient RISC entry, minimum immune response and off-target effects, efficient cellular uptake without formulation, and efficient and specific tissue distribution.