Universal Bases in siRNA for Rapid Evaluation of Sugar Modifications
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Solution Overview
Problem
Current RNA interference (RNAi) therapies face challenges due to the large molecular weight and polyanionic nature of siRNAs, which hinder cellular uptake and stability, and require optimization of potency, stability, and immunogenicity, with existing chemical modifications not effectively addressing siRNA/Ago2 binding considerations.
Innovation Solution
The use of universal bases in place of canonical heterocycles within siRNA oligomers, combined with sugar modifications, to simplify chemical synthesis and evaluate position-specific knockdown performance, allowing for rapid assessment of novel modifications that enhance siRNA stability and efficacy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If canonical heterocycles are used in siRNA oligomers, then binding affinity to target mRNA is maintained, but chemical synthesis complexity increases and position-specific performance evaluation becomes time-consuming
Solution Approach 1:
The patent uses universal bases (inosine, 6-amino-purine) as simplified copies or surrogates for the four canonical heterocycles (adenine, guanine, cytosine, uracil). These universal bases can pair with all canonical bases, allowing a single siRNA sequence with universal bases to evaluate positional effects without synthesizing four separate canonical sequences. This copying approach dramatically reduces synthesis time and enables rapid position-specific performance evaluation.
2Reliability
If chemical modifications are made to siRNA to improve stability and cellular uptake, then therapeutic potential increases, but understanding of siRNA/Ago2 binding interactions is compromised
Solution Approach 1:
The patent introduces universal bases as intermediary structures that mediate between the need for chemical modification stability and the need to understand canonical binding interactions. Universal bases maintain the structural framework and positional information needed for Ago2 binding studies while being chemically modifiable. They serve as intermediaries that preserve binding interaction information while allowing stability enhancements through sugar modifications and other chemical changes.
3Measurement precision
If multiple canonical nucleosides are synthesized to evaluate position-specific effects, then accurate binding data is obtained, but manufacturing complexity and cost increase
Solution Approach 1:
The patent applies universality by designing siRNA oligomers where one or more positions contain universal bases (inosine or 6-amino-purine) that can pair with all four canonical bases (A, U, C, G). This multi-functional universal base allows a single siRNA sequence to evaluate the positional effects of all four canonical nucleosides simultaneously, eliminating the need to synthesize and test four separate canonical sequences for each position. The universal base acts as a multi-functional surrogate that captures position-specific binding information without the complexity of multiple syntheses.
Data Source
AI summary
It is an object of the instant invention to provide a method for the rapid evaluation of novel sugar modifications to be used in siRNA synthesis including the rapid evaluation of chemical modification patterns within the siRNA to effectuate increased stability and ultimately increased efficacy of a siRNA therapeutic. It is a further object of the instant invention to provide novel nucleosides useful for siRNA therapy.