Endogenous RNA is central to protein control and, ultimately, cellular function. Synthetic RNA is an important tool for biological research and is also offering a new generation of promising therapeutic modalities to treat many inherited and acquired genetic and infectious diseases (Figure).

Figure. Chronological schematic of the advancements in RNA research leading to the development of new modalities.

Some of these target the cell’s RNA to impact protein expression by silencing genes, others target the DNA to cause genetic change, and others generate a selective immune response, such as chimeric antigen receptor (CAR) T cells against cancer or vaccines directed toward an infectious agent.

In this article, we describe these various modalities and the advances in therapy that have been enabled by RNA.

RNA for gene silencing

RNA interference (RNAi) is an endogenous cellular process in which double-stranded small interfering RNA molecules (siRNAs) bind to a specific mRNA target and trigger its degradation, resulting in reduced protein levels in the cell. This gene silencing method is allowing researchers to study the function of proteins within biological pathways by transiently removing them and analyzing the impact on cellular function.
While the biological regulatory function of the RNAi mechanism is still being studied, the use of synthetic siRNA oligos in therapeutics is becoming a good treatment option for viral diseases.1

Gene transcription control is also mediated using other endogenous RNA molecules, such as microRNAs (miRNAs) and small nuclear RNAs (snRNAs). snRNAs contribute to pre-mRNA splicing regulation rather than binding to mRNA and causing degradation. These RNA molecules are also available as synthetic gene modulators and are able to up- or down-regulate protein expression transiently.

RNA in gene editing

While RNAi has proven to be an effective tool for transient gene control, the discovery of CRISPR has revolutionized the field of permanent gene editing. The CRISPR-Cas9 system can be used in various gene editing applications, such as gene knock-out through the creation of stop codons or splice site variants. CRISPR is often used to validate gene function data that was initially obtained using RNAi approaches.

Ivonne Rubio, PhD

CRISPR has opened new possibilities in precision medicine. At the time of writing, the first CRISPR gene editing therapeutic has been approved by regulatory authorities for the treatment of sickle cell disease,2 and other clinical trials are currently underway to treat a wide variety of conditions including blood disorders, cancers, inherited eye disease, diabetes, infectious diseases, and inflammatory diseases.

CRISPR relies on the creation of a DNA double-strand break and homology-directed repair or the less desirable nonhomologous end joining for gene editing to occur. When editing of more than one target at a time is needed, there is an increased risk of unwanted genetic rearrangements including insertions and deletions (indels), increasing the possibility of adverse genetic changes that may increase cancer risk.

Base editing techniques that require only single-strand DNA breaks and offer precise DNA editing at the single-base level may offer a better safety profile. Because base editing systems are more tightly controlled, they offer the opportunity for simultaneous modification of several genes at once, offering a more streamlined editing system with improved tolerability in sensitive cells, such as stem cells.

Anis H. Khimani, PhD

Base editing can be used to silence disease-causing genes, to correct disease-associated point mutations, and to optimize the turnaround time and the yield of cell therapies.
All of the components for CRISPR and base editing can be delivered to the cell as synthetic RNA, making this a revolutionary and highly manufacturable therapeutic modality.

RNA to create cell therapies

Advances in gene editing have also enabled new developments in CAR T-cell therapies. By using gene editing on these therapeutic immune cells, researchers are improving their efficacy and persistence while reducing treatment-related toxicities. Scientists have even generated disease-specific CAR T cells in vivo by delivering modified mRNA encapsulated in T cell–targeting lipid nanoparticles. This approach has successfully reduced fibrosis and restored cardiac function in a mouse model of heart disease.3

Researchers are also exploring the role of epigenetic modifications of RNA and their implications in antiviral immunity, tumorigenesis, and cancer progression. For example, one of the most common and abundant transcriptional modifications of RNA that has been associated with tumorigenesis and drug resistance is N6-methyladenosine (m6A) RNA methylation.4 This epigenetic modification has been proposed as a prognostic marker for cancer or adverse drug response and as a novel target for therapeutics.

RNA in vaccines

One of the most well-documented therapeutic applications of RNA in recent years is its use in vaccines. The benefits of using mRNA vaccines include the flexible nature of the mRNA platform and the ability to efficiently deliver mRNA in vivo using lipid-based vehicles, allowing rapid uptake and expression in the cytoplasm, without a risk of genome integration and subsequent mutagenesis. Also, mRNA vaccines can be manufactured in a cell-free manner, allowing for rapid, scalable, and cost-effective production.

Michelle Fraser, PhD

The first mRNA vaccine was developed in 1995 for the treatment of cancer.5 It wasn’t until 2013 that the first clinical trial for a mRNA-based rabies vaccine was launched.6 Two years later, the first lipid nanoparticle (LNP)–formulated avian influenza mRNA vaccine was evaluated.7

However, during the COVID-19 pandemic, interest in mRNA-based vaccines spiked. In 2020, two SARS-CoV-2 vaccines from Moderna and Pfizer-BioNTech using mRNA encoding the virus spike protein as an immunogen received emergency use authorization or regulatory approval. Now, mRNA-based vaccines continue to be the focus of many SARS-CoV-2 vaccine strategies, as well as against other infectious diseases.
In the oncology field, mRNA cancer vaccines are being evaluated in combination with drugs that enhance the body’s immune response to tumors. Researchers are also exploring personalized vaccines that stimulate an antitumor response based on the mutational signature of a patient’s tumor and as therapies for autoimmune diseases.8


Given the success of the COVID-19 vaccines and the progress that has been made in understanding the role of RNA in health and disease, it is not surprising that RNA-based therapeutics have gained significant attention and are showing the potential to grow considerably. This growth is also being fueled by tools that enable the development and evaluation of RNA modalities.

For example, Revvity’s Dharmacon portfolio has been developing and manufacturing custom RNA for more than two decades. These include siRNA, shRNA, miRNA, CRISPR mRNAs, and guide RNAs and Pin-point™ base editing reagents.

Furthermore, the ongoing improved understanding of the mechanism of action of a range of RNA types, such as siRNA, shRNA, and miRNA, will continue to uncover novel causes of disease and offer emerging and potentially transformative therapeutic modalities.

In addition to the fundamental science and the multidisciplinary nature of future therapeutic modalities, collaboration at every level should be encouraged. Biotechnology, pharmaceutical, academic, and government organizations must consider how science, process development, informatics, supply chain, manufacturing, and regulatory interact. Hence, development teams ought to follow an integrated approach.

Ivonne Rubio, PhD, is a scientific support specialist based in Cambridge, U.K.; Anis H. Khimani, PhD, serves as senior strategy leader, life sciences, in Waltham, MA; and Michelle Fraser, PhD, is head of cell and gene therapy, in Boulder, CO. All three work for Revvity.

1. Hariharan, VN, et al.Divalent siRNAs are bioavailable in the lung and efficiently block SARS-CoV-2 infection. Proc. Natl, Acad. Sci. 2023, 120(11).

2. Frangoul H., et al. CRISPR-Cas9 gene editing for sickle cell disease and b-thalassemia. New Eng J Med 2021 Jan; 384: 252-60.

3. Rurik, JG, et al. 2022. CAR T cells produced in vivo to treat cardiac injury. Science. 2022 Jan;375(6576): 91-96.

4. Chen Z, Hu Y, Jin L, Yang F, Ding H, Zhang L, et al. The emerging role of N6-methyladenosine RNA methylation as regulators in cancer therapy and drug resistance. Frontiers in Pharmacology. 2022;13.

5. Conry RM, LoBuglio AF, Wright M, Sumerel L, Pike MJ, Johanning F, Benjamin R, Lu D, Curiel DT. Characterization of a messenger RNA polynucleotide vaccine vector. Cancer Res. 1995 Apr 1; 55(7): 1397-400.

6. Alberer M, Gnad-Vogt U, Hong HS, Mehr KT, Backert L, Finak G, Gottardo R, Bica MA, Garofano A, Koch SD, Fotin-Mleczek M, Hoerr I, Clemens R, von Sonnenburg F. Safety and immunogenicity of a mRNA rabies vaccine in healthy adults: an open-label, non-randomized, prospective, first-in-human phase 1 clinical trial. Lancet. 2017 Sep 23;390(10101):1511-1520.

7. Feldman RA, Fuhr R, Smolenov I, (Mick) Ribeiro A, Panther L, Watson M, et al. MRNA vaccines against H10N8 and H7N9 influenza viruses of pandemic potential are immunogenic and well tolerated in healthy adults in phase 1 randomized clinical trials. Vaccine. 2019;37(25):3326–34.

8. Krienke C, Kolb L, Diken E, Steuber M, Kirchhoff S, Bukur R, Akilli-Öztürk Ö, Kranz LM, Berger H, Pechenga J, Diken M, Kreiter S, Yogev N, Waisman A, Karikó K, Türeci Ö, and Sahin U. A noninflammatory mRNA vaccine for treatment of experimental autoimmune encephalomyelitis, Science 2021; 371(6525):145-153.

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