GalNAc-siRNA Conjugates: Leading the Way for Delivery of RNAi Therapeutics
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Published on: July 23, 2016
Aaron D Springer1, Steven F Dowdy1
1Department of Cellular and Molecular Medicine, University of California San Diego , La Jolla, California.
Abstract:
Short-interfering RNA (siRNA)-induced RNAi responses have great potential to treat a wide variety of human diseases from cancer to pandemic viral outbreaks to Parkinson's Disease. However, before siRNAs can become drugs, they must overcome a billion years of evolutionary defenses designed to keep invading RNAs on the outside cells from getting to the inside of cells. Not surprisingly, significant effort has been placed in developing a wide array of delivery technologies. Foremost of these has been the development of N-acetylgalactosamine (GalNAc) siRNA conjugates for delivery to liver. Tris-GalNAc binds to the Asialoglycoprotein receptor that is highly expressed on hepatocytes resulting in rapid endocytosis. While the exact mechanism of escape across the endosomal lipid bilayer membrane remains unknown, sufficient amounts of siRNAs enter the cytoplasm to induce robust, target selective RNAi responses in vivo. Multiple GalNAc-siRNA conjugate clinical trials, including two phase III trials, are currently underway by three biotech companies to treat a wide variety of diseases. GalNAc-siRNA conjugates are a simple solution to the siRNA delivery problem for liver hepatocytes and have shown the RNAi (and antisense oligonucleotide) field the path forward for targeting other tissue types.
Insights
N-acetylgalactosamine (GalNAc) siRNA conjugates effectively deliver short-interfering RNA (siRNA) to liver cells by targeting the Asialoglycoprotein receptor. This breakthrough enables robust RNA interference (RNAi) responses, paving the way for new disease treatments.
Area of Science:
- Biotechnology
- Molecular Biology
- Drug Delivery
Background:
- Short-interfering RNA (siRNA) holds therapeutic potential for various diseases, including cancer and viral infections.
- siRNA drug development is hindered by cellular defenses against external RNA, necessitating effective delivery systems.
- Targeting specific tissues remains a challenge for siRNA-based therapies.
Purpose of the Study:
- To explore the efficacy of N-acetylgalactosamine (GalNAc) siRNA conjugates for targeted delivery to liver cells.
- To investigate the mechanism of siRNA entry into hepatocytes and subsequent RNA interference (RNAi) activation.
- To assess the clinical potential of GalNAc-siRNA conjugates for treating liver-related diseases.
Main Methods:
- Development of GalNAc-siRNA conjugates for targeted liver delivery.
- Utilizing the Asialoglycoprotein receptor (ASGPR) highly expressed on hepatocytes for receptor-mediated endocytosis.
- Monitoring siRNA entry into the cytoplasm and subsequent induction of RNAi responses in vivo.
Main Results:
- Tris-GalNAc conjugates efficiently bind to ASGPR on hepatocytes, leading to rapid endocytosis.
- Sufficient siRNA quantities successfully enter the cytoplasm to elicit potent, target-specific RNAi.
- Multiple clinical trials are ongoing, demonstrating the therapeutic promise of GalNAc-siRNA conjugates.
Conclusions:
- GalNAc-siRNA conjugates represent a significant advancement in siRNA delivery, specifically for liver-targeted therapies.
- This approach overcomes cellular barriers, enabling effective RNAi in vivo.
- The success of GalNAc-siRNA conjugates provides a roadmap for targeting other tissues and advancing RNAi-based medicine.
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