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Millions of Americans with high cholesterol now have a new treatment option, as the FDA has approved the first once-daily oral PCSK9 inhibitor.

Merck, the New Jersey-based manufacturer of Lipfendra (enlicitide), announced the approval on Thursday.

Lipfendra blocks the action of PCSK9, a naturally occurring protein that affects how the liver removes LDL ("bad") cholesterol from the bloodstream.

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"PCSK-9 is a protein that works in the liver, preventing the recycling of LDL receptors, as a result increasing bad cholesterol in the blood," Dr. Marc Siegel, Fox News senior medical analyst, told Fox News Digital.

Millions of Americans with high cholesterol now have a new treatment option, as the FDA has approved the first once-daily oral PCSK9 inhibitor. (iStock)

"In the caveman days, this was useful when we were hunter-gatherers and didn't always have food, but now it mainly forms plaques that lead directly to heart disease."

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The pill is approved as an add-on to diet and other LDL-lowering therapies in adults with high cholesterol, including inherited forms of high cholesterol, Merck stated.

In phase 3 clinical trials, Lipfendra was shown to reduce LDL cholesterol by up to 60% in patients on statin therapy.

The drug was very well-tolerated in the two phase 3 trials, Merck reported. In the larger study with a broad population of patients, the side effect profile was similar to placebo. In a smaller study of patients with a genetic form of high cholesterol, the researchers reported that a small numbers of patients experienced diarrhea and dizziness.

The pill was generally well-tolerated in the trials, Merck reported. The most common side effects were diarrhea and dizziness, while serious side effects and treatment discontinuations occurred at rates similar to those in the placebo group. (iStock)

Statins, which work by blocking an enzyme in the liver that the body uses to make cholesterol, are the most commonly prescribed cholesterol-lowering medications, according to the American Heart Association.

For many people, statins are effective on their own. But for some patients who have very high cholesterol levels, inherited forms of high cholesterol or adverse side effects when taking statins, another medication — such as a PCSK9 inhibitor like Lipfendra — may be necessary, per the AHA.

Lipfendra blocks the action of PCSK9, a naturally occurring protein that affects how the liver removes LDL ("bad") cholesterol from the bloodstream. (iStock)

Until now, PCSK9 inhibitors — such as Repatha and Praluent — have only been available as injections, a factor experts say may have contributed to their underuse.

"Repatha, the injectable form, is very useful, with few side effects," Siegel noted. "The oral form, Lipfendra, is also well-tolerated and just as effective."

Additional research is needed to determine whether Lipfendra also reduces the risk of heart attacks, strokes and cardiovascular deaths. Results from a large clinical trial are expected to be available in 2029, Merck stated. (Merck & Co.)

Additional research is needed to determine whether Lipfendra also reduces the risk of heart attacks, strokes and cardiovascular deaths. Results from a large clinical trial are expected to be available in 2029, Merck stated.

"Steve Nissen, longtime head of preventive cardiology at Cleveland Clinic, tells me that the lower the better when it comes to LDL cholesterol, especially in those at risk for heart disease," Siegel added.

Melissa Rudy is senior health editor and a member of the lifestyle team at Fox News Digital. Story tips can be sent to melissa.rudy@fox.com.

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