Vaccines have been reliably and affordably protecting people from diseases worldwide for centuries. Until the COVID-19 pandemic, however, vaccine development was still a long and idiosyncratic process. Traditionally, researchers had to tailor manufacturing processes and facilities for each vaccine candidate, and the scientific knowledge gained from one vaccine was often not directly transferable to another.
But the COVID-19 mRNA vaccines brought a new approach to vaccine development that has far-reaching implications for how researchers make drugs to treat many other diseases.
I am a biochemist, and my lab at UMass Chan Medical School focuses on developing better ways to use mRNA as a drug. Although there are many possibilities for what researchers can use mRNA to treat, some important limitations remain. Better understanding how mRNA-based drugs interact with the immune system and how they are degraded in human cells can help lead to safe, durable and effective treatments for a wide range of diseases.
Some basics of mRNA drugs
Messenger RNA, or mRNA, is made of four building blocks denoted by the letters A, C, G and U. The sequence of letters in an mRNA molecule conveys genetic information that directs how a protein is made.
An mRNA drug comprises two essential components: mRNA molecules, which code for desired proteins, and the lipid molecules – such as phospholipids and cholesterol – that encapsulate them. These mRNA-lipid nanoparticles, or LNPs, are tiny spheres about 100 nanometers in diameter that protect mRNA from degradation and facilitate its delivery into target cells.
Once inside cells, mRNA molecules instruct the cell’s machinery to produce the target protein required for a desired therapeutic effect. For example, the mRNA in the Pfizer-BioNTech and Moderna COVID-19 vaccines directs cells to produce a harmless version of the virus’ spike protein that trains the immune system to recognize and better prepare for potential infection.
The science behind COVID-19 mRNA vaccines has been decades in the making.
From a drug development perspective, mRNA drugs offer significant advantages over traditional drugs because they are easily programmable. Hundreds of pounds of mRNA can be made from readily available DNA templates, such that producing a different mRNA drug is as simple as changing the corresponding DNA templates.
More importantly, different mRNA drugs produced by the same set of methods will have similar properties. They will be delivered to the same tissues, trigger similar levels of immune responses and degrade in similar ways. This predictability significantly reduces the development risks and financial costs of developing mRNA drugs.
In addition to being easy to program, mRNA drugs have several other unique properties. For example, just like the mRNAs your body naturally produces, therapeutic mRNAs have a short half-life in cells:
