The Crispr components can’t naturally get into cells on their own, so Intellia uses a delivery system called lipid nanoparticles—essentially tiny fat bubbles—to ferry them to the liver. In Intellia’s trials, patients receive a one-time IV infusion of these Crispr-laden nanoparticles into the veins in their arms. Since blood passes through the liver, lipid nanoparticles can easily travel there from the bloodstream. In the liver, the nanoparticles are taken up by cells called hepatocytes. Once inside these cells, the nanoparticles break down and let Crispr get to work editing out the problematic gene.

In both diseases, a genetic mutation allows an aberrant protein to run amok and cause damage. In hereditary angioedema, Intellia’s Crispr treatment is designed to knock out the KLKB1 gene in liver cells, which reduces the production of kallikrein protein. Too much kallikrein leads to the overproduction of another protein, called bradykinin, which is responsible for recurring, debilitating, and potentially fatal swelling attacks.

According to an Intellia press release, before receiving a Crispr infusion, patients experienced one to seven swelling attacks per month. During a 16-week observational period, the Crispr infusion reduced those attacks by an average of 91 percent.

In transthyretin amyloidosis, mutations in the TTR gene cause the liver to produce abnormal versions of the transthyretin protein. These damaged proteins build up over time, causing serious complications in tissues including the heart, nerves, and digestive system. One type of the disease can lead to heart failure and affects between 200,000 to 500,000 people worldwide. By the time patients are diagnosed with the disease, they’re expected to live just two to six more years.

Intellia’s Crispr treatment is designed to inactivate the TTR gene and reduce the buildup of the disease-causing protein it makes. Vaishali...