Two-tailed siRNA with Phosphorothioate Tails for Brain Delivery
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Solution Overview
Problem
There is a need for robust and non-toxic delivery of RNAi therapeutics, particularly to the central nervous system, to effectively treat neurological and other diseases, as existing methods lack specificity and efficiency in targeting specific cell types in vivo.
Innovation Solution
Development of novel two-tailed, chemically-modified siRNA compounds with overhanging phosphorothioated tails, which demonstrate enhanced uptake and distribution after injection, allowing for targeted delivery to specific tissues like the brain without the need for lipid formulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single-tailed siRNA is used for delivery, then the structure is simpler, but distribution and retention in brain tissues is insufficient
Solution Approach 1:
The siRNA is divided into two separate strands (sense and antisense) with distinct functional regions. The antisense strand contains the phosphorothioated overhang tail for targeted delivery, while the sense strand provides structural support and stability. This segmentation allows each component to perform its specific function optimally, achieving both improved brain tissue distribution and maintained structural simplicity.
Solution Approach 2:
The phosphorothioated overhang tail is localized specifically to the 3' end of the antisense strand, concentrating the delivery-enhancing properties at the precise location needed for cellular uptake and brain tissue penetration. This localized modification improves distribution without requiring complex changes to the entire siRNA structure.
2Stability of the object's composition
If chemically-modified nucleotides are incorporated, then nuclease resistance and stability are improved, but manufacturing complexity increases
Solution Approach 1:
The chemical modification changes the parameter of the phosphate backbone by replacing one oxygen atom with sulfur (phosphorothioate modification). This single atomic substitution provides significant nuclease resistance improvement while maintaining compatibility with standard oligonucleotide synthesis methods, thus balancing stability enhancement with manufacturing feasibility.
3Productivity
If phosphorothioated overhang tails are added to both strands, then uptake and distribution are enhanced, but the risk of off-target effects increases
Solution Approach 1:
The siRNA structure employs asymmetry by placing phosphorothioated overhang tails specifically on the antisense strand while keeping the sense strand tail-free or with different modifications. This asymmetric design enhances uptake and distribution efficiency through the modified strand while the unmodified sense strand maintains sequence specificity, thereby reducing off-target effects.
Solution Approach 2:
The phosphorothioated overhang tail is copied only on the antisense strand rather than duplicating modifications on both strands. This selective copying approach maximizes delivery efficiency through the modified strand while preserving the specificity function of the unmodified sense strand, thus balancing productivity improvement with harm reduction.
Data Source
AI summary
Provided are compositions and methods comprising two-tailed siRNAs (tt-siRNAs) that exhibit unprecedented cellular uptake and silencing. Also provided are methods of treating neurological and other diseases with the two-tailed siRNAs of the invention.