Messenger RNA gave us a COVID-19 vaccine. Will it treat diseases, too?
The dramatic success of two COVID-19 vaccines in clinical trials last month marked a triumph for a previously unproven medical technology. The vaccines, one of which was authorized for emergency use by the U.S. Food and Drug Administration last week, rely on the genetic instructions known as messenger RNA (mRNA). It prompts cells to make a SARS-CoV-2 protein that trains the immune system to recognize the virus.
But long before the pandemic, mRNA tantalized pharma, promising a simple and flexible way to deliver both vaccines and drugs. One mRNA sequence might mend a damaged heart by producing a protein that stimulates blood vessel growth. Another might encode a missing enzyme to reverse a rare genetic disease. Now, the vaccine wins have created a “tsunami” of enthusiasm around the concept, says pharmaceutical scientist Gaurav Sahay of Oregon State University, Corvallis.
But mRNA medicines—especially those that replace beneficial proteins for chronic disease—have a tougher road to the clinic than vaccines. These drugs face the challenges of targeting mRNA to specific tissues and giving strong, lasting benefits without excessive side effects. Few have made it to clinical trials. “It’s not like you just put in another sequence and it will treat anything,” says Heleen Dewitte, a pharmaceutical scientist at Ghent University. 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.
For vaccines and some mRNA drugs, administration is relatively simple. After a jab in the arm, muscle cells take up mRNA and crank out a viral protein. The immune system sees the protein as foreign and produces antibodies and T cells that arm the body against future invasion. Aside from SARS-CoV-2, mRNA vaccines against rabies, Zika, cytomegalovirus, influenza, and other viruses are advancing through clinical trials.
A 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. 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.
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