PCSK9 inhibitors

PCSK9 inhibitors (sometimes also shown as PCSK9i) are a new type of medicine for lowering cholesterol in the blood.

PCSK9 is a protein that’s made in the liver. Research has shown that people with high levels of PCSK9 tend to have high cholesterol throughout their lives and develop heart disease early. But people with low levels tend to have low cholesterol and a lower risk of heart disease. This discovery has led to the development of medicines called PCSK9 inhibitors to lower cholesterol.

There are two PCSK9 inhibitors, Repatha (Evolocumab) and Praluent (Alirocumab), and others are being developed at the moment.

In clinical studies, these medicines have lowered people’s cholesterol levels by more than half. Early research shows they could prevent strokes and heart attacks too.

Who can take PCSK9 inhibitors?

Your doctor might suggest you take PCSK9 inhibitors if you have very high levels of cholesterol in your blood and you are at risk of early heart disease.

For example, if you:

  • have already had a heart attack, stroke or another disease of the blood vessels, and other medicines such as statins and ezetimibe haven’t lowered your cholesterol enough
  • have familial hypercholesterolaemia (FH) and your treatment isn’t bringing your cholesterol levels down low enough
  • you have high cholesterol and other medications for cholesterol aren’t working well, they’re giving you side effects, or you have another health problem which means you can’t take them.

You can take PCSK9 inhibitors alongside other treatments, such as statins, to lower cholesterol.

How do PCSK9 inhibitors work?


Our liver cells have LDL receptors on the outside of them. These receptors attach to LDL cholesterol (sometimes called 'bad cholesterol') when it passes by in the blood. The receptor takes the cholesterol out of the blood and into the liver to be broken down. The more LDL receptors we have, the easier it is for us to keep our blood cholesterol low.

The PCSK9 protein breaks down the LDL receptors, so that we have less of them – meaning our cholesterol goes up. PCSK9 inhibitors act on the PCSK9 protein and stop it from working so that we have more working LDL receptors and less cholesterol in the blood.

Taking PCSK9 inhibitors

PCSK9 inhibitors can be prescribed by a specialist doctor in a lipid clinic.

They are given by injection once every two to four weeks. Your doctor or nurse will show you how to give the injection yourself so that you don’t need to go to hospital or your GP surgery for the injections.

After two to three months, you will have an appointment and a blood test to see how well the PCSK9 inhibitors are working. If they're working well, you’ll then have appointments less often, perhaps once a year.

Side effects of PCSK9 inhibitors

All medicines can have side effects, including PCSK9 inhibitors, but clinical studies have shown that they usually cause very few side effects. 

The most common side effects, which affect less than 1 in 10 but more than 1 in 100 people, are:

  • flu-like symptoms such as cold, nausea, back and joint pain
  • soreness or itchiness where you give the injection
  • muscle pain.