RNAi: The Benefits of Shooting the Messenger

In 2006, Andrew Fire and Craig Mello shared the Nobel Prize in Physiology or Medicine for their discovery of RNA interference (RNAi), which they published in 1998. Since then, the potential of a technology capable of silencing disease-causing genes has been a very attractive proposition.

It was not until 2018 that the US Food and Drug Administration (FDA) approved the first therapy developed using the technique. Since then, there’s been a steady, but slow, number of RNAi treatments coming into the market. This November is likely to see the approval of Arrowhead Pharmaceutical’s (ARWR) first commercial product. This development marks a compelling point for precision medicine, as we may be about to see the floodgates open for a lot of previously untreatable diseases.

How RNAi Intercepts the Instructions

First, let’s start with a massively oversimplified biology lesson: Part of normal human function consists of molecules called messenger RNA (mRNA), which grab a copy from the DNA stored in the cell’s nucleus and bring those instructions to a ribosome. The ribosome then “prints” proteins required for day-to-day bodily functions.

By now, we have probably heard at some point that disease X is caused by a mutation in gene Y. In other words, the instructions have led to either faulty proteins or the overproduction of healthy ones. The solutions in these cases are three: We can edit the gene directly (gene therapy), address the wonky proteins being created by the printer (traditional small molecule/biologic drugs), or intercept the mRNA bringing those instructions before they get to the printer (RNAi).

Let’s use a leaky faucet analogy. Traditional therapies would mop up the puddle under the pipe on a fixed schedule, RNAi would tighten the faucet for the leak to temporarily stop, while gene therapies would replace the faucet altogether. It is then no secret why the therapeutic use of RNAi would be so attractive.