Messenger ribonucleic acid (mRNA) is a single stranded molecule responsible for transferring genetic information from deoxyribonucleic acid (DNA) to ribosomes. Ribosomes then decode genetic information and synthesize proteins. The mRNA therapy to be discussed here refers to the use of mRNA based drugs developed for the treatment or prevention of diseases.

In recent years, the technology of in vitro transcription (IVT) of mRNA has gradually attracted the interest and attention of scientists in research institutions and R&D departments of biopharmaceutical companies. Biomedical companies use mRNA based technology platforms to develop targeted drug delivery methods, making drugs more precise and personalized. And with the collaboration of genetic engineering, researchers can use synthesized mRNA to express specific proteins. Due to the structural similarity of synthesized mRNA to natural mRNA, patients are able to produce therapeutic proteins in their own bodies and reduce various troubles caused by the complex manufacturing process of recombinant proteins. Based on the diversity of mRNA based therapies, new drug developers have made progress in developing immunotherapy for cancer treatment, stem cell therapy and infectious disease control by using synthetic mRNA as a disease treatment tool. Especially during the COVID-19 pandemic, mRNA based technology has obvious advantages in vaccine research and development.

In the 1960s, cellular and molecular biology made significant progress. The discovery of messenger RNA (1961), the subsequent discovery of RNA related replicases and reverse transcriptase (1962, 1970), and the discovery and application of RNA splicing and catalytic ribozymes (1977, 1982) directly or indirectly promoted the development of mRNA based new drugs. After more than 30 years of continuous scientific progress, RNA based drugs were tested on animal bodies. First, Wolff et al. completed the research on using mRNA molecules for therapeutic purposes in 1990, which is widely recognized as the earliest application. In this study, IVT mRNA was directly injected into the skeletal muscle of mice and expressed as the encoded protein. The article points out that due to the repeated acquisition of RNA and tissue, RNA based therapy can transfer the determined reversible type of gene transfer into the patient's cells to prevent or treat specific diseases. Subsequently, a series of milestone experiments revealed the potential of RNA based therapy, including injecting influenza mRNA to induce immune responses in mice (1993), injecting mRNA vaccines for anti-cancer research in mice (1995), and using modified RNA to inhibit hepatitis C virus in mice (2002). These groundbreaking studies have perfected the development of mRNA based therapy in different fields.

The improvement of lipid nanoparticle (LNP) carrier technology also greatly promotes the development of mRNA based therapy. LNP is an emerging drug carrier, and its applications have also expanded to innovation and development in other fields, such as medical imaging. The earliest LNP for nanomedicine delivery platform from concept to clinical application should be liposomes. Because liposomes can transport hydrophobic or hydrophilic molecules, including small molecules, proteins, and nucleic acids, they have become an extremely versatile carrier platform. In the development of anti-tumor drugs, liposomes have reduced the side effects of drug delivery and improved patient tolerance, but have not significantly improved patient survival rates. In the early 1990s, with the development of nanoscience and nanotechnology, LNP gradually began to be applied. Overall, lipid nanoparticles and liposomes have similar designs, both of which are lipid nanoparticles and drug delivery carriers. They can protect drugs from damage by the human immune system, mimic biofilms, and give drugs more time to reach their intended targets. Secondly, they all have pharmacological properties that help dissolve highly lipophilic molecules or regulate drugs, thereby minimizing drug induced side effects and improving drug safety. LNP and liposomes have slight differences in composition and function, and their applications are more diverse.

In the past two decades, mRNA based technology for cancer treatment has gradually gained attention and been fully developed. Through continuous optimization, remarkable progress has been made in the research of cancer, rare diseases, genetic diseases, and infectious diseases based on mRNA technology. In August 2018, Patisiran, the first small interfering RNA based drug, received approval from the US FDA for the treatment of multiple neurological disorders caused by hereditary transthyretin amyloidosis (hATTR). This is a milestone market approval based on RNA therapy. SiRNA refers to small double stranded RNAs that can be split into single strands and bind to their intended target mRNA, causing the mRNA to break and degrade, hence also known as RNA interference (RNAi) therapy.

Patisiran is an siRNA formulated into LNP, which then binds to apolipoprotein E (APOE) receptors and is absorbed by liver cells. It further cleaves and breaks down the mRNA of transthyretin through interfering RNA, thereby reducing the production of transthyretin in circulation and its deposition in tissues and organs. In ATTR amyloidosis patients, disordered overlapping transthyretin accumulates in various tissues in the body, such as peripheral nerves and the heart, causing damage to organs and tissues, leading to neuropathy and cardiomyopathy. So far, in addition to Patisiran, there are three other RNAi drugs approved for marketing in the United States to treat some rare diseases, such as acute porphyria hepatica (AHP), primary hyperoxaluria type 1 (PH1), familial hypercholesterolemia (HeFH) or clinical atherosclerotic cardiovascular disease (ASCVD).

In the past few years, mRNA based therapy has achieved remarkable results in the field of infectious diseases, including the use of nucleoside modified mRNA for immunotherapy against infections such as human immunodeficiency virus (HIV), cytomegalovirus (CMV), and human papillomavirus (HPV).

During this period, in vitro mRNA transcription methods based on mRNA therapy gradually matured. There are currently two commonly used and stable methods. One method is to transfer mRNA ex vivo into the patient's cells, and then transfuse these cells back to the patient. This method is commonly used in genomic engineering, gene reprogramming, or cell-based (T cells and dendritic cells) immune cell anti-cancer research. Another method is to directly deliver transcribed mRNA in vitro for research in the treatment of tumors and infectious diseases, allergic tolerance, and other protein replacement therapies. In addition to the above achievements in the treatment of rare diseases, the mRNA vaccine also shows its advantages of high efficiency and safety in reducing COVID-9 infection and preventing its severity. Compared to traditional vaccines, mRNA vaccines based on synthesis are more effective, without the risk of integration into human DNA, and have the advantages of short research and development cycles, simple production processes, and low manufacturing costs. This makes mRNA vaccines more attractive in stimulating immune responses, reducing infection rates or severe cases.

2 ► mRNA based therapy - now available

Since the COVID-19 pandemic, the mRNA vaccine has successfully replaced the traditional vaccine and developed into a revolutionary new drug. Driven by the overall increase in healthcare and research and development expenditures, there has been a surge in mRNA based vaccine development. The first mRNA vaccines to receive Emergency Use Authorization (EUA) were Comirnaty developed by Pfizer/BioNTech (December 2020) and Spikevax developed by Moderna (December 2020). Subsequently, the mRNA vaccines that have obtained local emergency use rights continue to emerge. GEMCOVAC-19 of Gennova Biopharma in India (June 2022), AWcora of Watson Biopharma in China (October 2022), and COVID-19 mRNA vaccine of Sri Lanka (December 2022) were authorized by local drug supervision authorities for emergency use respectively. Not only in the fight against COVID-19 infection, but also in the fight against HIV infection, mRNA technology began to launch (NIH News, March 14, 2022). The Phase III clinical trial on the prevention of respiratory diseases caused by respiratory syncytial virus (RSV) also showed that vaccines developed through mRNA technology have good safety and clinical efficacy (Moderna News, January 17, 2023).

Driven by the growing interest of various stakeholders and encouragement of clinical practice, the RNA based therapy and vaccine market is expected to continue growing before 2035, with the potential for scientific advancements and breakthrough drug candidates in RNA molecular biology. Currently, over 35 companies are involved in the clinical development of more than 195 mRNA based therapies or vaccines at different stages, targeting different diseases. It can be expected that in the next decade, some RNA based therapies will continue to emerge and be commercialized in clinical practice. Due to the continuous success of RNA therapies, investors have shown increasing interest in investing in biotechnology companies engaged in mRNA technology; At the same time, biotechnology companies will invest funds in improving mRNA technology platforms, streamlining operations, and providing a wider range of services to promote their healthy development. The active participation of multinational pharmaceutical companies in mRNA technology and drug development is also crucial, and research and development pipelines will continue to grow. The main leading biotechnology companies in this field worldwide include BioNTec (Germany, 2008, 1200), Moderna (United States, 2005, 760), CureVac (Germany, 2007, 700), Microorganisms (China, 2016, 500), ImmoRNA (United States, 2019, 200), Omega Medical (United States, 2017, 200), eTheRNA (Belgium, 2013, 50), Blue Magpie Biotech (China, 2019, 50), Chimeron Biotech (United States, 2015, 10+).

As mentioned earlier, developing emerging therapeutic methods based on mRNA technology has some advantages, such as the ability to engineer candidate drugs to deliver mRNA molecules that encode functional proteins and can replace defective proteins. The main advantages are as follows:

MRNA therapy has the potential to restore gene expression or alter the genome without entering the nucleus;

MRNA therapy does not require intracellular transcription, which makes it less prone to errors, thus achieving faster gene translation;

The expression of mRNA is transient and controllable, attributed to the fact that mRNA cannot replicate in principle, thereby reducing overexpression or any related chance side effects;

Compared with other nucleic acid based therapies such as DNA, mRNA therapy has better transfection ability, providing better expression opportunities and higher success rates;

MRNA therapy has the potential to cure diseases that are currently incurable, mainly by using the cell's own mechanisms to produce natural and abundant functional proteins;

MRNA therapy has drug like properties that can simplify dosage changes and repetitive adjustments;

MRNA therapy involves selecting target genes and candidate products, so its development will be relatively faster.

Although mRNA therapy provides many benefits, current research and development still encounter many problems. In addition to the need to improve the stability of candidate drugs and address technical difficulties related to targeted delivery, other major issues include limited professional knowledge and talent, lack of demand for professional infrastructure, high capital investment requirements and restrictions, and unclear and inconsistent production standards (GMP). In addition, the current market driven design of mRNA based therapies mainly relies on intramuscular administration, and it seems unlikely that this trend will change significantly, at least not as much as expected in the near future. Moreover, mRNA based therapies have the largest market share in the global market in the field of infectious diseases, while they still lack absolute advantages in tumors or rare diseases. However, regardless, the increasing development of RNA based therapies in different disease fields indicates that this technology has a very wide range of applications and is currently a highly active research field. The advancement of biotechnology and the resulting molecular advantages greatly drive research and development work based on RNA therapy. Compared with other treatment methods, RNA based therapy not only has a multifunctional delivery platform, but also demonstrates high efficacy, high immunogenicity, and low toxicity. As mentioned above, RNA therapy has a low risk of causing accidental infections in infectious diseases, and the possibility of insertion mutagenesis is small. Secondly, the in vivo half-life of mRNA can be regulated through bioengineering, allowing for different modifications or improvements in drug delivery methods to make drugs more stable. Thirdly, it has high transcribability and is usually degraded by typical cellular activities, thereby reducing the risk of long-term presence in the body. Fourthly, due to the high yield of in vitro transcription reactions, the production and manufacturing of candidate drugs through mRNA technology have good cost-effectiveness, speed, and scalability.

Vaccination is one of the major successes of modern medicine. For example, the prevalence of infectious diseases such as measles decreases with the vaccination schedule, while smallpox is basically eliminated after vaccination. Despite the great success of traditional vaccines, these methods are still not very effective against rapidly mutating pathogenic microorganisms, such as influenza virus, Ebola virus, or Zika virus, which remains a huge public health hazard for the world. Once these viruses become prevalent, they will bring huge disasters to the world. However, traditional vaccines have the following drawbacks: (1) they require a lengthy, complex, and expensive process. Cultivate target pathogens/antigens in specialized cell culture and/or fermentation based production processes, followed by extraction, inactivation, isolation, and purification. (2) Although it shows empirical effectiveness, the exact mechanism for protecting the human body is unclear in most cases. (3) Specific strict production processes, complex production facilities, and rigorously trained operators are required. However, the shortcomings of these traditional vaccines can basically be overcome by mRNA based vaccines, which can be manufactured in a shorter time, have lower production costs, and have better anti infectious disease efficacy. MRNA based vaccines have multiple advantages,