Messenger RNAs—molecules that carry information between the genome and the protein-building machinery of cells—could become the next big class of biopharmaceutical drug.

These molecules were once thought unusable as drugs because they are notoriously fragile and could rouse an inflammatory immune response. Now, thanks to several recent scientific discoveries, they are attracting the increasing attention of pharmaceutical companies.

Recently, the pharmaceutical heavyweight AstraZeneca announced it would pay Moderna Therapetuics $240 million for rights to the startup’s mRNA technology, which it will use to develop treatments for cardiovascular, metabolic, and cancer patients.