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The current state and future directions of RNAi-based therapeutics

An Author Correction to this article was published on 24 April 2019

A Publisher Correction to this article was published on 18 March 2019

This article has been updated


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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Fig. 1: Early events in the discovery and elucidation of the RNAi pathway.
Fig. 2: Pathways for mammalian miRNA biogenesis, synthetic RNAi trigger processing and RNAi silencing.
Fig. 3: Representative secondary structure motifs of different classes of synthetic RNAi triggers along with their primary mechanisms of entry into the RNAi pathway.
Fig. 4: The therapeutic mechanism of patisiran.
Fig. 5: RNAi-based therapeutics beyond siRNA.

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.

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Correspondence to Si-ping Han.

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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.

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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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Setten, R.L., Rossi, J.J. & Han, Sp. The current state and future directions of RNAi-based therapeutics. Nat Rev Drug Discov 18, 421–446 (2019).

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