Messenger RNA (mRNA) therapy is an approach that has gained significant attention due to its success immunizing people against COVID-19 variants. This methodology utilizes mRNA molecules to instruct cells in the body to produce specific proteins that can be used by the immune system to build immunity.

mRNA therapies incorporate synthetic nucleotides that resist degradation and reduce immunogenicity. They are delivered into cells via advanced lipid-based packaging and can be bulk manufactured in relatively short time. As a therapeutic strategy, mRNA shows applicability for a wide range of indications. Furthermore, because the mRNA molecules do not integrate into the genome, they have a favorable safety profile, reducing the risk of unintended genetic mutations.

How does mRNA therapy work?

Synthetic mRNA molecules are made of modified nucleotide sequences designed to mimic the structure and function of natural mRNA molecules. They are produced through in vitro transcription, where the DNA sequence encoding the desired protein is transcribed into an mRNA molecule. The resulting synthetic mRNA molecule is then purified and packaged for delivery to the body.

Once administered using lipid-based delivery vehicles, the mRNA molecules are taken up by cells. The instructions they carry are translated into nascent proteins by the cell's own ribosome machinery. Therapeutic proteins can be displayed on the cell’s surface or secreted into the extracellular environment. In the case of vaccines, the antigens produced by mRNA encoding viral proteins instruct the immune system to mount a response against the pathogen from which they were derived.

Therapeutic mRNA applications include gene editing functions like those provided by the CRISPR-Cas9 system.

Advantages of mRNA therapy

• High specificity: Lipid nanoparticles can be designed with ligands or receptors on their surface that allow them to be taken up by specific cells. This ensures that the mRNA payload is delivered to the site of interest (e.g., tumor).

• Rapid development: Compared to traditional drug development methods, mRNA therapies can be rapidly developed and manufactured.

• Low mutagenicity: mRNA molecules do not integrate into the host genome, reducing the risk of an insertional mutagenesis.

• Versatility: mRNA therapy has the potential to treat a wide range of indications, including cancer, infectious diseases and genetic disorders.

mRNA therapeutics - Design and synthesis

The process of making mRNA therapeutics is relatively short in duration yet requires specialized technologies and expertise for manufacturing steps. mRNA molecules intended for therapeutic applications require thorough design, synthesis and packaging specifications to ensure optimal delivery and in vivo translation.

1. Design: Bioinformatics tools are used to design optimal mRNA sequences that result in therapeutic protein expression.
2. Synthesis: Once the mRNA sequence is designed, it is typically synthesized in vitro using a DNA template that is transcribed with RNA polymerases.
3. Purification: The synthesized mRNA is then purified to remove any contaminants, ensuring the mRNA is of high quality and free of impurities.
4. Formulation: The purified mRNA is formulated with other materials, such as cationic lipids or polymers, to protect it from degradation and improve its delivery to cells.

mRNA Therapeutics - Cell delivery

Synthetic mRNA is delivered to target cells using lipid delivery vehicles. Lipids protect mRNA molecules from degradation and facilitate their uptake into cells. Advances in lipid nanoparticle technology are expanding the possibilities for creating safe and effective mRNA-based therapeutics with improved delivery and therapeutic potential.

Some examples of lipid delivery vehicles used in mRNA therapy:

1. Liposomes: Liposomes are spherical structures made of a lipid bilayer that can encapsulate mRNA molecules. Liposomes can improve the stability and bioavailability of mRNA molecules and can also target specific cell types through modification with targeting ligands.
2. Lipid Nanoparticles (LNPs): LNPs are lipid-based nanoparticles composed of an mRNA molecule core surrounded by a lipid bilayer shell that can facilitate uptake into cells.
3. Solid Lipid Nanoparticles (SLNs): SLNs are like LNPs but use solid lipids and are covered by a surfactant. SLNs have higher stability and can protect mRNA molecules from degradation for extended periods.
4. Ethanolamine-Based Lipids: These cationic lipids can form stable complexes with mRNA molecules and effectively deliver mRNA-based vaccines.

One major challenge that a synthetic mRNA faces is that when it is introduced into cells, it can become trapped in endosomes, which are small membrane-bound compartments inside cells responsible for transporting and breaking down cellular material. If the mRNA is not able to escape from the endosome, it will degrade and not translate.

Synthetic mRNAs designed for therapeutic applications can overcome this challenge. Chemical modifications, such as pseudouridine, can be introduced into a synthetic mRNA molecule to make it more stable and resistant to degradation. This can help the mRNA survive longer inside the cell and increase the likelihood of successful translation. Endosome-disrupting agents, such as chloroquine or bafilomycin A1, can be used to prevent the endosome from breaking down the mRNA. This can increase the amount of mRNA available for translation and promote optimal expression.

Clinical Applications of mRNA therapy

mRNA therapy has the potential to revolutionize the treatment of various diseases by using a patient's own cells to produce proteins that can prevent or treat the condition. Some developing mRNA therapy clinical applications include:

1. Cancer Immunotherapy: mRNA cancer therapy is being investigated to stimulate the immune system to recognize and attack cancer cells.
2. Genetic or Rare Diseases: mRNA therapy has the potential to treat genetic disorders and rare diseases caused by a faulty or missing protein. The patient’s cells can produce the missing protein by delivering mRNA that codes for that protein and potentially alleviate the disease symptoms to improve the patient’s quality of life.
3. Infectious Diseases: mRNA vaccines can be developed against ligands expressed on the surface of infectious agents for the immune system to recognize them and mount an attack.
4. Cardiovascular Diseases: mRNA therapy has the potential to treat cardiovascular diseases by delivering mRNA that codes for proteins that promote blood vessel growth or reduce inflammation.

Overall, mRNA therapy can potentially transform the treatment of various diseases and has already shown promising results in research studies and clinical trials. New mRNA therapy investigations include regenerative medicine to repair damaged tissues, treating neurological diseases such as Alzheimer’s and Parkinson’s and providing remedies for chronic disorders such as diabetes and heart disease.

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