202409220002 Status: #article Tags: Title: RNA Therapeutics (Wikipedia) Author: ---- # RNA Therapeutics (Wikipedia) ## What Kind of Article Practical / Expository ## Summary ## Outline - **The main types of RNA therapeutics are based on** - **Messenger RNA (mRNA)** - Responsible for bringing genetic data (i.e. one codon of 3 nucleotides) to ribosomes to produce amino acids. Comes as a result of the transcription step. The administration of a nucleoside-modified mRNA sequence can cause a cell to make a protein, which in turn could directly treat a disease or could function as a vaccine - mRNA-based therapy is the only type which is based on triggering synthesis of proteins within cells, making it particularly useful in vaccine development - DNA therapeutics needs access to the nucleus to be transcribed into RNA, and its functionality depends on nuclear envelope breakdown during cell division. However, mRNA therapeutics do not need to enter into the nucleus to be functional since it will be translated immediately once it has reached to the cytoplasm. Moreover, unlike plasmids and viral vectors, mRNAs do not integrate into the genome and therefore do not have the risk of insertional mutagenesis, making them suitable for use in cancer vaccines, tumor immunotherapy and infectious disease prevention - **Mechanisms:** In vitro transcription (IVT) is performed on a linearized DNA plasmid template containing the targeted coding sequence. Then, naked mRNA or mRNA complexed in a nanoparticle will be delivered systemically or locally. Subsequently, a part of the exogenous naked mRNA or complexed mRNA will go through cell-specific mechanisms. Once in the cytoplasm, the IVT mRNA is translated by the protein synthesis machinery - **Challenge:** primary challenges of RNA therapy center on delivering the RNA to the appropriate cells. These challenges include: - Naked RNA sequences naturally degrade after preparation - RNA sequences may trigger the body's immune system to attack them as an invader - RNA sequences are impermeable to the cell membrane. - **Solution:** methods that have been researched to improve the delivery system of mRNA are using [microinjection](https://en.wikipedia.org/wiki/Microinjection "Microinjection"), RNA patches (mRNA loaded in a dissolving micro-needle), [gene gun](https://en.wikipedia.org/wiki/Gene_gun "Gene gun"), [protamine](https://en.wikipedia.org/wiki/Protamine "Protamine") condensation, RNA [adjuvants](https://en.wikipedia.org/wiki/Adjuvant "Adjuvant"), and encapsulating mRNA in nanoparticles with lipids - **Antisense RNA (asRNA)** - asRNA is a single-stranded RNA that is complementary to a protein coding mRNA with which it hybridizes and thereby blocks its translation into protein. The primary function of asRNA is regulating gene expression. asRNAs have found widespread use as research tools for gene knockdown (an experimental technique by which gene expression of one or more of an organism's genes is reduced) - asRNAs can also be promising targets for drugs. Drugs tend to downregulate whatever they bind to (by blocking some function of the molecule when they bind to it). Hence, it has historically been difficult to use drugs to *upregulate* desired genes, such as tumor suppressor genes and neuroprotective growth factors. Drugs can then target asRNAs and downregulate their blocking of specific mRNAs to, in turn, upregulate those genes. This should, in theory, be easier than the current approaches of enzyme replacement therapies and microRNA therapies. - **RNA interference (RNAi)** - RNAi is a biological process in which RNA molecules are involved in sequence-specific suppression of gene expression by double-stranded RNA, through translational or transcriptional repression. microRNA (miRNA) and small interfering RNA (siRNA) are central components to the RNAi pathway. There is a growing class of siRNA-based drugs that decrease the expression of proteins encoded by certain genes - **Small interfering RNAs (siRNAs)** are short, 19-23 base-pair (with a 3' overhang of two nucleotides), double-stranded pieces of RNA that participate in the RNA-induced silencing complex (RISC) for gene silencing. Specifically, siRNA is bound by the RISC complex where it is unwound using ATP hydrolysis. It is then used as a guide by the enzyme "Slicer" to target mRNAs for degradation based on complementary base-pairing to the target mRNA - **Micro RNAs (miRNAs)** are short, ~19-23 base pair long RNA oligonucleotides that are involved in the microRNA-induced silencing complex. Specifically, once loaded onto the ARGONAUTE enzyme, miRNAs work with mRNAs to repress translation and post-translationally destabilize mRNA. While they are functionally similar to siRNAs, miRNAs do not require extensive base-pairing for mRNA silencing (can require as few as seven base-pairs with target), thus allowing them to broadly affect a wider range of mRNA targets. In the cell, miRNA uses switch, tuning, and neutral interactions to finely regulate gene repression. As a therapeutic, miRNA has the potential to affect biochemical pathways throughout the organism. - **RNA aptamers** - RNA aptamers are oligomers (molecules consisting of a few repeating subunits that could be derived from monomers) that bind to a specific target molecule or family of target molecules. Aptamers and antibodies can be used in many of the same applications, but the nucleic acid-based structure of RNA aptamers is very different from the amino acid-based structure of antibodies. This difference can make aptamers a better choice than antibodies for some purposes. - Aptamers are much smaller in size and mass than antibodies, which could be a relevant factor in choosing which is best suited for a given application. When aptamers are available for a particular application, their advantages over antibodies include potentially lower immunogenicity, greater replicability and lower cost, a greater level of control due to the _in vitro_ selection conditions, and capacity to be efficiently engineered for durability, specificity, and sensitivity. - Because aptamers are nucleic-acid based, they can be directly synthesized, eliminating the need for cell-based expression and extraction as is the case in antibody production ## Thoughts & Ideas ## Criticisms --- # References