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In ornithine transcarbamylase (OTC) deficiency, for example, a missing enzyme causes a buildup of ammonia in the blood that can lead to seizures, coma, and death. Propionyl-CoA carboxylase, needed for normal metabolismĬas9, which cuts DNA to remove a defective geneīut many other mRNA medicines have to find their way to a specific site in the body via the bloodstream. OTC, which helps remove nitrogen from the body VEGF-A, which stimulates blood vessel growth Here are some.ĬFTR, which maintains fluid balance across membranes Message in a bottleĪlthough dozens of trials are testing messenger RNA to arm the immune system against viruses or cancer, only a few companies have launched small clinical trials of other therapies-such as mRNA to replace missing or defective proteins. More than a dozen clinical trials are underway for such therapies, which encode tumor proteins or immune signaling molecules to help ramp up the body's attack on cancer cells. Aside from SARS-CoV-2, mRNA vaccines against rabies, Zika, cytomegalovirus, influenza, and other viruses are advancing through clinical trials.Ī local injection-into muscle, under the skin, or into a tumor-can also deliver some mRNA-based therapies that harness the immune system to fight cancer. The immune system sees the protein as foreign and produces antibodies and T cells that arm the body against future invasion. After a jab in the arm, muscle cells take up mRNA and crank out a viral protein. Tailoring an mRNA medicine to a disease often means tweaking the structures of both the mRNA itself and the protective bubble commonly used to ferry it through body, known as a lipid nanoparticle.įor vaccines and some mRNA drugs, administration is relatively simple. "It's not like you just put in another sequence and it will treat anything," says Heleen Dewitte, a pharmaceutical scientist at Ghent University. These drugs face the challenges of targeting mRNA to specific tissues and giving strong, lasting benefits without excessive side effects. Now, the vaccine wins have created a "tsunami" of enthusiasm around the concept, says pharmaceutical scientist Gaurav Sahay of Oregon State University, Corvallis.īut mRNA medicines-especially those that replace beneficial proteins for chronic disease-have a tougher road to the clinic than vaccines. Another might encode a missing enzyme to reverse a rare genetic disease. One mRNA sequence might mend a damaged heart by producing a protein that stimulates blood vessel growth. It prompts cells to make a SARS-CoV-2 protein that trains the immune system to recognize the virus.īut long before the pandemic, mRNA tantalized pharma, promising a simple and flexible way to deliver both vaccines and drugs. Food and Drug Administration last week, rely on the genetic instructions known as messenger RNA (mRNA).

The vaccines, one of which was authorized for emergency use by the U.S. The dramatic success of two COVID-19 vaccines in clinical trials last month marked a triumph for a previously unproven medical technology.