Heart disease remains the leading cause of death in the United States, killing more than 600,000 people annually, according to the Centers for Disease Control and Prevention. (BigStock)

The Food and Drug Administration on Friday approved the first in a new class of cholesterol-busting drugs that many doctors believe will trigger a breakthrough in reducing the incidence of strokes and heart attacks, which kill hundreds of thousands of Americans each year.

The new medications are known as PCSK9 inhibitors because they block a substance that hinders the liver’s ability to remove bad, or LDL, cholesterol from the blood. In clinical trials, the drugs have shown an ability to reduce bad cholesterol levels by as much as 60 percent, even for some people taking statin drugs, which have been the standard medication for high cholesterol for decades.

Still, because PCSK9 drugs are so new, there are no definitive answers yet about whether their cholesterol-lowering effects actually will translate into fewer heart attacks, strokes and other heart problems. Over the next couple years, studies already underway should begin to give a clearer picture about such long-term outcomes.

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For now, that lack of data is partly why the FDA approved Praluent -- developed through a partnership between drug companies Sanofi and Regeneron -- only for a limited set of patients. The agency said the drug could be used for people with heterozygous familial hypercholesterolemia, an inherited disorder that can severely elevate LDL levels, as well as for patients who have had heart attacks and other serious cardiovascular problems and still cannot reach target LDL levels through the use of statins.

Later in the summer, the FDA is expected to approve a second PCSK9 drug developed by Amgen; that drug already was approved by European regulators earlier this week. Global pharmaceutical giant Pfizer has yet another PCSK9 drug in the pipeline.

“The FDA strongly supports continued work to provide new and innovative options for the treatment and prevention of cardiovascular disease," John Jenkins, director of the FDA's Office of New Drugs, said in a statement Friday.

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Jay Edelberg, head of the PCSK9 development unit at Sanofi, said in an interview that the new drug represents "a breathtaking revolution" for certain patients who have been unable to get their bad cholesterol to desirable levels, despite taking the maximum dosage of statins.

"The clinical studies we've done to date really have shown exactly what we've hoped for, which is a truly unprecedented ability to lower LDL cholesterol," he said. "The ability to lower LDL for these high-risk patients is incredibly important."

Edelberg said the company is conducting a trial involving 18,000 patients around the globe who already are taking statins but not at their target cholesterol levels. That trial, expected to wrap up by the end of 2017, should show whether the new drugs actually help prevent heart attacks and stroke.

Even before Friday's approval, the potential cost of the new cholesterol drugs has caused consternation among insurers and others in the health care industry. Statin drugs, which have long been available in generic form, can cost as little as $4 a day.

Sanofi on Friday disclosed that it plans to charge $40 a day, or more than $14,000 a year, for its PCSK9 drug, which is intended for patients still in need of lowering their bad cholesterol levels even after taking statins.

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That price is far less than expensive specialty drugs for cystic fibrosis, certain cancers and hepatitis C, but potentially a massive collective cost given the drugs could eventually treat large numbers of patients and must be taken indefinitely.

Dan Durham, interim head of the trade group America’s Health Insurance Plans, said in a statement Friday that the price of the PCSK9 drug “raises concerns as to whether consumers and the health system can sustain the long-term cost.”

Steven Pearson, president of the Institute for Clinical and Economic Review, a nonprofit that assesses the value of new treatments, said his group would study the new cholesterol drug in coming months in an effort to evaluate if the benefits of the drug justify its price tag.

"We don't know [yet] if we are getting good value with these new drugs to manage cholesterol," Pearson said. "We will look at that ... At the end of the day, what matters is the health that it brings to patients.”