A study published in the Journal of the American Chemical Society in 2014 describes the development of multivalent N-acetylgalactosamine (GalNAc)-conjugated siRNA that effectively targets hepatocytes and induces robust RNAi-mediated gene silencing. The research team, led by Jayaprakash K. Nair and colleagues from Alnylam Pharmaceuticals and the University of California, Los Angeles, designed and synthesized chemically modified siRNA-GalNAc conjugates that can be delivered subcutaneously (SC) with high efficacy and minimal side effects. The GalNAc ligand, derived from N-acetylgalactosamine, is a highly efficient ligand for the asialoglycoprotein receptor (ASGPR), which is expressed on hepatocytes. The conjugates were synthesized using solid-phase oligonucleotide synthesis and deprotection conditions, resulting in high yields comparable to standard oligonucleotides. The conjugates were shown to be stable against nucleases and to have improved pharmacokinetics compared to unconjugated siRNAs. In vitro and in vivo studies demonstrated that the siRNA-GalNAc conjugates efficiently enter hepatocytes and silence target genes, including those encoding apolipoprotein B 100 (ApoB100) and mouse transthyretin (mTTR). The conjugates were effective in silencing mTTR mRNA in the liver after SC administration, with over 80% suppression of TTR mRNA in mice following a single dose. The conjugates also showed sustained gene silencing for over 9 months with no adverse effects in rodents. The study highlights the potential of chemically modified siRNA-GalNAc conjugates as a novel class of RNAi therapeutics with demonstrated preclinical efficacy in vivo. The conjugates can be delivered subcutaneously, which is more convenient and less invasive than intravenous administration. The research also shows that the ASGPR can be efficiently recycled for multiple rounds of siRNA uptake, enabling robust and sustained gene silencing. The findings suggest that the ASGPR is a promising target for chronic SC treatment of liver-expressed genes.A study published in the Journal of the American Chemical Society in 2014 describes the development of multivalent N-acetylgalactosamine (GalNAc)-conjugated siRNA that effectively targets hepatocytes and induces robust RNAi-mediated gene silencing. The research team, led by Jayaprakash K. Nair and colleagues from Alnylam Pharmaceuticals and the University of California, Los Angeles, designed and synthesized chemically modified siRNA-GalNAc conjugates that can be delivered subcutaneously (SC) with high efficacy and minimal side effects. The GalNAc ligand, derived from N-acetylgalactosamine, is a highly efficient ligand for the asialoglycoprotein receptor (ASGPR), which is expressed on hepatocytes. The conjugates were synthesized using solid-phase oligonucleotide synthesis and deprotection conditions, resulting in high yields comparable to standard oligonucleotides. The conjugates were shown to be stable against nucleases and to have improved pharmacokinetics compared to unconjugated siRNAs. In vitro and in vivo studies demonstrated that the siRNA-GalNAc conjugates efficiently enter hepatocytes and silence target genes, including those encoding apolipoprotein B 100 (ApoB100) and mouse transthyretin (mTTR). The conjugates were effective in silencing mTTR mRNA in the liver after SC administration, with over 80% suppression of TTR mRNA in mice following a single dose. The conjugates also showed sustained gene silencing for over 9 months with no adverse effects in rodents. The study highlights the potential of chemically modified siRNA-GalNAc conjugates as a novel class of RNAi therapeutics with demonstrated preclinical efficacy in vivo. The conjugates can be delivered subcutaneously, which is more convenient and less invasive than intravenous administration. The research also shows that the ASGPR can be efficiently recycled for multiple rounds of siRNA uptake, enabling robust and sustained gene silencing. The findings suggest that the ASGPR is a promising target for chronic SC treatment of liver-expressed genes.