SCAD: A modular platform for efficient delivery of duplex RNA to the CNS and beyond.

Oligonucleotide therapeutics-including antisense oligonucleotides and duplex RNAs such as small interfering RNAs, small activating RNAs, and microRNAs-hold immense potential for treating both genetic and acquired diseases by modulating gene expression in a target-specific manner. However, effective delivery to extrahepatic tissues, particularly the central nervous system, remains a significant challenge. While N-Acetylgalactosamine conjugation has enabled liver-specific delivery of oligonucleotides leading to several approved siRNA drugs for hepatic indications, there remains a significant unmet need for effective treatment options in the CNS space. We have developed the smart chemistry-aided delivery platform that enables duplex RNA delivery by conjugating to an accessory oligonucleotide, which facilitates protein binding and promotes cellular uptake. Through extensive screening, we identified an optimal SCAD architecture that demonstrates enhanced cell-free protein binding and in vitro activity. In rodent models, local administration of SCAD-siRNA conjugates resulted in broad biodistribution throughout the CNS and sustained mRNA knockdown for over 5 months, with a favorable safety profile. The SCAD platform also exhibited efficient delivery to other extrahepatic tissues, including the eye, lung, and joint. The modular design of SCAD can be easily adapted to any duplex RNA, making it a powerful tool for advancing oligonucleotide therapeutics.