What are RNA drugs?

RNA drugs refer to RNA with the function of treating diseases, which can directly regulate the expression of the disease genes from the source, which is one of the effective means of precision medicine. RNA drugs mainly include small interfering RNA, small activated nucleic acids, mRNA drugs, ribozymes, etc.

• siRNA drugs

In October 2018, the world's first RNAi drug Patisiran (trade name ONPATTRO®) was approved by the US FDA for the treatment of hereditary thyroxine-mediated amyloidosis polyneuropathy. The launch of this product marks that the in vivo delivery of RNAi therapy has been solved, proving the clinical application value and commercial development value of RNAi technology. In November 2019, Alnylam announced that its new RNAi therapy drug GIVLAARI (trade name GIVOSIRAN®) has been approved by the US FDA for the treatment of adult acute hepatic porphyria. This is the second RNAi therapy drug approved globally.

RNAi technology once again shows its huge potential for disease treatment. At present, there are many siRNA drugs in clinical stage in the world.

• saRNA drugs

The small dsRNA with gene activation function is called small activating RNA (saRNA). Compared with the silencing effect of RNAi, the activation of RNAa is more durable, and it provides a new idea and method for the treatment of tumors, metabolism, and genetic diseases.

RNA activation (RNAa) was first discovered by Dr. Li Longcheng of the University of California, San Francisco, and David Corey of the University of Texas at Southwest in 2006. The British company MiNA obtained the two-person patent authorization and launched the world's first clinical trial of saRNAs drug MTL-CEBPA against liver cancer with a low response rate and high recurrence rate in 2016. The preclinical data of the MTL-CEBPA project shows that the compound can promote the reversal of the disease process in several liver disease models and reduce the tumor burden of liver cancer. At present, the clinical trial of MTL-CEBPA combined with sorafenib in the treatment of liver cancer has progressed to clinical phase two.

• mRNA drugs

The use of mRNA as a drug can guide intracellular protein expression or extracellular protein secretion. It is fundamentally different from other types of drugs to treat diseases. mRNA therapy can not only treat diseases caused by gene defects through the expression of functional proteins, but also can be used in vaccines by expressing viral or tumor antigen proteins, especially in large-scale sudden Virus infections, tumor vaccines, and personalized vaccines have great potential. Another characteristic of mRNA drug is that they change the way new drugs are developed in terms of speed and scale. In the study of new coronavirus vaccines in early 2020, most of the leading ones were mRNA vaccines.

• Ribozyme

Ribozyme is a type of small-molecule RNA with biocatalytic activity, which can specifically degrade target mRNA, thereby blocking the expression of specific genes.

Compared with other RNAs, ribozymes have a relatively stable three-dimensional structure and are not easily attacked by RNases. More importantly, after the ribozyme cuts the mRNA, it can be freed from the hybrid chain, and then recombine and cleave other mRNA molecules. This means that the activity of ribozymes in the body is high, and only a small amount is required to function.

There are many types of ribozymes. From the structural point of view, they can be divided into two types. One is hairpin ribozymes. The cleavage activity requires a minimum length of 50 nucleotides, of which 15 are necessary. The ribozyme of this structure is usually composed of four-helix regions and several ring-binding regions; the other is the hammerhead ribozyme, which is about 30 nucleotides long, has three base-paired helix regions, and two single-strand Region and a bulged nucleotide.

As a method of gene therapy, ribozymes have been tested for HIV, HBV, HCV, HDV, etc.. in addition, some experiments have used ribozymes to treat leukemia in mice have achieved good results. However, for some unclear reasons, no ribozyme drugs have hit the market so far.

RNA drugs, as a treatment method that can directly affect the pathological process at the genetic level, are expected to become another explosive product after small molecule drugs and monoclonal antibodies.