Doctors have been telling their patients for what seems like eons to fight heart disease by quitting smoking, treating blood pressure, becoming more active and eating a healthy diet. You'd think we might have come up with something better by now. But no. Heart disease remains a leading cause of Canadian mortality, accounting for about a quarter of all deaths. And it's been frustratingly stuck in that position for a long time.
Now, a new class of drugs has the potential to transform the way we think about lowering cholesterol levels--and the fight against heart disease. Health Canada approved in September the first drug of the class, known by the brand name Repatha and the generic name, evolocumab. A second drug that is know by the brand name Praluent and the generic name, alirocumab, was approved by the FDA in July and should be approved soon for use in Canada.
The two drugs belong to a class of drugs known as PCSK9 inhibitors, which lower blood cholesterol levels in a completely new way. Cholesterol, of course, is one of the main factors in heart disease. There are various types, but the real contributor is LDL cholesterol, a sticky molecule in the blood that contributes to plaque buildup in the arteries. Lower LDL cholesterol levels correspond to a lower risk of developing heart disease.
Increasing number of doctors are counselling their patients to focus on lifestyle and overall risks rather than simply lowering LDL cholesterol scores. All the same, some of my patients get positively maniacal about cutting their counts. One way to lower your LDL score is by eating better -- cutting out saturated fats and processed foods, and eating lots of fruits and vegetables.
Pharmaceuticals can also help. Many of my patients lower their cholesterol with drugs called statins, the best-known of which is Lipitor. In fact, if you listen to some doctors, nearly everyone over 50 should be on a statin, which have been on the market since the late 1980s.
But statins aren't taken by everyone. Some patients worry about side effects, like muscle pain, or don't want to take a daily medication. And their potency is limited. Statins decrease LDL cholesterol levels between 30 and 50 per cent on average.
Hence, the search for a more potent cholesterol-lowering agent--which lead to these new PCSK9 inhibitors. The origin of the discovery is pretty fascinating. Our livers have receptors that naturally filter LDL cholesterol from the blood. But then scientists discovered a naturally occurring protein called PCSK9, which prevents the liver's receptors from cleansing the blood of the bad cholesterol. Researchers then discovered that some people -- about 2.5 per cent of black people --had a genetic mutation that prevented PCSK9 from messing with the liver. The result was abnormally low LDL cholesterol scores, and what seemed like an immunity to heart disease.
Pharmaceutical companies raced to copy the mutation's effect, resulting in the new drugs, alirocumab and evolocumab. To paraphrase a great observation by an American MD, the only cardiologists who aren't excited about these new drugs are dead. Clinical trials have seen these drugs reducing LDL cholesterol levels by about 60 per cent.
Some aspects of the new drugs prevent them, at this point, from being the panacea that some are predicting they'll be. The drugs are human monoclonal antibodies, which can be tricky to make in mass quantities -- so they're more expensive. For now, they can only be administered as injections, once or twice a month.
But at this point, these new PCSK9 inhibitors are looking like they have the potential to transform heart disease prevention. "We are entering a new and exciting era in the prevention world," says Dr. Beth Abramson, the cardiologist who leads the cardiac prevention centre at St. Michael's Hospital. "We should keep in mind however, that these newer medications have a role in addition to statins, which are proven to reduce risk."
Dr. Erin Michos, associate director of preventive cardiology at Baltimore's Johns Hopkins University, agrees with the hype--but only for the right type of patients, such as those with something called familial hypercholesterolemia, an inherited condition that makes it difficult to lower LDL cholesterol levels by traditional means.
It's too soon to prescribe PCSK9 inhibitors for lower-risk patients, Dr. Michos says. "The PSCK9 studies so far have been short-term," she says. "Longer-term studies are needed to confirm that these drugs really do prevent heart attacks and save lives without significant side effects."
In fact, PCSK9 inhibitors are so effective that some docs are worrying they may decrease LDL cholesterol too much. Cholesterol is used to build cell membranes and make hormones, among other functions. Is it possible we may need some minimum levels of LDL cholesterol for our bodies to work properly? Sure. We'll need to do more research to identify what that minimum level is.
If your cholesterol score is proving tricky to lower, and you've tried other methods, then it's possible these drugs can help you. And the next trick? Cutting the costs for these drugs as effectively as the drugs cut cholesterol levels -- solve that, and we'll be that much closer to a revolution in cardiac care.
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