Review Article | Published:

The current state and future directions of RNAi-based therapeutics

Nature Reviews Drug Discovery (2019) | Download Citation


The RNA interference (RNAi) pathway regulates mRNA stability and translation in nearly all human cells. Small double-stranded RNA molecules can efficiently trigger RNAi silencing of specific genes, but their therapeutic use has faced numerous challenges involving safety and potency. However, August 2018 marked a new era for the field, with the US Food and Drug Administration approving patisiran, the first RNAi-based drug. In this Review, we discuss key advances in the design and development of RNAi drugs leading up to this landmark achievement, the state of the current clinical pipeline and prospects for future advances, including novel RNAi pathway agents utilizing mechanisms beyond post-translational RNAi silencing.

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Alnylam 2014 presentation on GalNAc-siRNA with Enhanced Stabilization Chemistry:

Alnylam 2017 presentation on ESC + GalNAc siRNA:

Alnylam 2018 presentation on CNS preclinical data:

Alnylam announcement of top-line phase III clinical trial results for givosiran:

Alnylam presentation on nonclinical evaluation of GalNAc-siRNAs:

Alnylam report on Investigation of Mortality Imbalance in Revusiran Phase III Study, ENDEAVOUR:

Alnylam RNAi pipeline:

Arrowhead Pharmaceuticals presentations:

Codiak Biosciences product pipeline:

Dharmacon siDESIGN Center:

Dicerna GalXC technology platform:

IDT DNA custom DsiRNA design center:

Martin Maier (Alnylam) presentation at Precision Nanosystems 2018 Symposium: = 8msoAVIPVWU

US National Institutes of Health website on primary hyperoxaluria:

Reuters news on withdrawal of ARC-520, ARC-521 and ARC-AAT:

Silence Therapeutics presentations:

siDirect web portal:

Quark Pharmaceuticals product pipeline:

Change history

  • 24 April 2019

    Errors in the alignment and structure of the siRNN and in the structure of the sisiRNA in the original version of Fig. 3 have been corrected.

  • 18 March 2019

    The use of the names for patisiran has been made consistent throughout the article in line with the journal style and typographical errors have been corrected.


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This work was funded by US National Institutes of Health grant AI29329 and US National Science Foundation Emerging Frontiers in Research and Innovation (EFRI)–Origami Design for Integration of Self-assembling Systems for Engineering Innovation (ODISSEI) award 133241.

Author information


  1. Department of Molecular and Cellular Biology, Beckman Research Institute, City of Hope, Duarte, CA, USA

    • Ryan L. Setten
    • , John J. Rossi
    •  & Si-ping Han
  2. Irell and Manella Graduate School of Biological Sciences, City of Hope, Duarte, CA, USA

    • Ryan L. Setten
    •  & John J. Rossi
  3. Materials and Process Simulation Center, California Institute of Technology, Pasadena, CA, USA

    • Si-ping Han


  1. Search for Ryan L. Setten in:

  2. Search for John J. Rossi in:

  3. Search for Si-ping Han in:

Competing interests

J.J.R. is a co-founder of Dicerna Pharmaceuticals and MiNA Therapeutics. S.-p.H. and J.J.R. are inventors on US patents and patent applications for conditional RNA interference-related technologies.

Corresponding author

Correspondence to Si-ping Han.


Small interfering RNAs

(siRNAs). Short (19–21 bp) RNA duplexes with two-base 3ʹ overhangs that trigger RNA interference without Dicer cleavage.

Hereditary transthyretin amyloidosis

(hATTR). A rare inherited condition caused by deposition of amyloid fibrils formed by misfolded transthyretin protein monomers.

Endosomal escape

The escape of RNA interference agents from endosomes into the cytosol.

RNA-induced silencing complex

(RISC). Protein RNA complexes that serve as the effectors of RNA interference. RISCs are composed of an Argonaute (Ago) protein with an inserted RNA guide strand and other proteins complexed with Ago.

Guide strand

An RNA strand that is inserted into an Argonaute protein to form a mature RNA-induced silencing complex.

Antisense strand

The strand in an RNA interference trigger that is complementary to the intended target.

Sense strand

The strand in an RNA interference trigger that is homologous to the intended target.

Dicer substrate siRNAs

(DsiRNAs). RNA duplexes of 22–29 bp with a two-base 3ʹ overhang on the putative guide strand that trigger RNA interference via cleavage by Dicer.


(PS). A nucleic acid backbone modification in which one oxygen in the phosphodiester is replaced by a sulfur atom.


(Ago). One of four different proteins, Ago1–Ago4, that bind to RNA interference guide strands to form RNA-induced silencing complexes.

Passenger strands

The complements to the guide strands that are discarded during strand selection.

Antisense oligonucleotides

(ASOs). Synthetic single-stranded oligonucleotides of varying chemistries for which the sequence specifically hybridizes with target RNAs.


(2′-O-me). A naturally occurring modification of RNA in which a methyl group is added to the 2′ hydroxyl of the ribose sugar.


(2ʹ-F). A synthetic analogue of RNA in which the 2ʹ hydroxyl on the sugar is replaced by a fluorine.


(2′-MOE). A synthetic analogue of RNA in which a 2-methoxyethyl group is attached to the 2ʹ hydroxyl.

Locked nucleic acid

(LNAs). A synthetic analogue of RNA in which a methylene bridge connects the 2′ oxygen and the 4′ carbon.

Unlocked nucleic acid

(UNA). A synthetic acyclic analogue of RNA missing the C2′–C3′ bond of the ribose ring.


A charge-neutral analogue of DNA in which backbone phosphodiesters are replaced with phosphorodiamidate linkages.

Peptide nucleic acid

(PNA). A synthetic analogue of DNA and RNA that has a peptide backbone.

2ʹ-Deoxy-2ʹ-fluoro-β-d-arabinonucleic acid

(FANA). A synthetic nucleotide in which the 2′ sugar position is a stereoisomer of DNA with an additional fluorine group.


Molecular features that determine pharmacokinetics.


Molecular features that determine pharmacodynamics.


(GalNAc). A sugar derivative of galactose that binds to the asialoglycoprotein receptor on hepatocytes.


The nonspecific cellular uptake of single-stranded oligonucleotides, especially those with phosphorothioate backbones.


The exit of pharmaceutical agents from the systemic circulation into the extracellular space.


Disrupts the integrity of the endosomal membrane, leading to membrane rupture.


Induces the fusion of lipid vesicles. These are typically less disruptive of endosomal membranes than endosomolytic agents.

Transcriptional gene silencing

(TGS). Direct epigenetic silencing of a target gene’s promoter induced by either small interfering RNAs or microRNAs.

Small activating RNAs

(saRNAs). Short double-stranded RNAs that induce transcription of a target gene in an Argonaute 2-mediated process called RNA activation.

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