A protein called PCSK9 causes the liver to break down fewer 'bad' cholesterol carriers, which means more of it stays in your blood.

People born with a certain gene change that breaks the PCSK9 gene tend to have much lower 'bad' cholesterol their whole lives and are far less likely to get heart disease — so scientists think blocking this gene with medicine might help protect others' hearts too.

PCSK9 inhibitors can help lower bad cholesterol, either when added to other treatments or used instead of them.

PCSK9 doesn't just raise bad cholesterol — it also directly worsens artery disease by making immune and blood vessel cells absorb more damaged fats, reducing their ability to clean out cholesterol, and increasing inflammation in the arteries.

A protein called PCSK9 helps break down the liver's 'LDL cholesterol cleaners,' so more bad cholesterol stays in your blood, raising heart disease risk. People with certain PCSK9 gene changes either have very high or very low cholesterol levels.

Some cholesterol drugs called PCSK9 inhibitors also lower another harmful fat in the blood called lipoprotein(a), and that might help protect the heart in ways that aren't just about lowering bad cholesterol.