Modified dsRNA with Nucleotide Overhangs for Serum Stability

The patent applies parameter changes by modifying the chemical structure of nucleotides within the dsRNA molecule. Specifically, it incorporates nucleotides with 2′-O-alkyl modifications (such as 2′-O-methyl, 2′-O-ethyl, 2′-O-propyl groups) and locked nucleotide analogs that alter the sugar pucker and conformational flexibility. These chemical parameter modifications increase resistance to nucleases while maintaining RNAi activity, thereby improving stability and half-life in serum without sacrificing gene silencing effectiveness

The patent employs composite materials by creating dsRNA molecules that combine modified nucleotides with unmodified nucleotides in specific ratios and positions. The composite structure includes 2′-O-alkyl modified nucleotides, locked nucleotide analogs, and natural nucleotides arranged to optimize both stability and RNAi function. This composite approach allows the molecule to benefit from the enhanced nuclease resistance of modified components while retaining the functional capabilities of natural RNA structures

The patent applies local quality by strategically placing modified nucleotides at specific positions within the dsRNA sequence rather than uniformly modifying all nucleotides. The modifications are concentrated at the 3′ ends of the strands and at positions most susceptible to nuclease attack, while internal regions may use unmodified or less complex modifications. This localized approach maximizes protective effect while minimizing synthesis complexity and cost

The patent implements partial action by incorporating modified nucleotides at specific percentages (e.g., 1-10 modified nucleotides per 22-nucleotide strand) rather than full modification. This partial modification approach provides sufficient nuclease resistance to achieve the desired stability improvement while keeping synthesis procedures manageable and costs acceptable for therapeutic development