Studies of a new class of experimental cholesterol-lowering drugs signal that they may reduce by half the risk of heart attack and other major cardiovascular problems compared to standard treatment alone.
Doctors at the annual meeting of the American College of Cardiology, where the studies were presented, called the results "encouraging", but said larger, controlled trials were needed to fully understand the drugs, known as PCSK9 inhibitors.
An analysis of about 4 500 patients who continued treatment for nearly a year after completing earlier trials of Amgen Inc's Repatha, also known as evolocumab, found that 0.95 percent of patients given the drug and standard therapy suffered a cardiovascular event, compared with 2.18 percent of the group receiving standard treatment, which ranged from dietary changes to drugs such as statins.
Amgen defined "event" in the study as death, heart attack, stroke or "mini-stroke," unstable chest pain or heart failure requiring hospitalisation, or the need for a procedure to restore blood flow to the heart.
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Side effects more frequent, but still rare, in patients treated with Repatha included neurocognitive problems - something the U.S. Food and Drug Administration has said should be monitored closely.
"We have been looking at this throughout our clinical program," Scott Wasserman, Amgen's head of cardiovascular and metabolic therapies told Reuters. "We have not identified what we believe is a safety issue."
Neurocognitive side effects were also more common in the treatment arm of an 18-month, 2,300-patient trial of a rival PCSK9 drug being developed by Sanofi SA and Regeneron Pharmaceuticals Inc.
Reduced risk of cardiovascular problems
The drug, Praluent, was shown to reduce the risk of cardiovascular problems from 3.3 percent for placebo patients to 1.7 percent for the treatment group. "Events" in this trial were defined only as death, heart attack, stroke and chest pain requiring hospitalisation.
"Some of the endpoints in these trials are kind of soft, and they aren't prospective studies," said Dr. Anthony DeMaria, director of the cardiovascular centre at the University of California San Diego who was not involved in the trials. "It's encouraging that the larger trials are likely to succeed, but we still need those trials."
Dr Marc Sabatine, lead investigator of the Repatha study, said data for both drugs "are very consistent ... it appears that cutting LDL by 61 percent translates to a roughly 50 percent reduction in cardiovascular events."
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The experimental drugs are antibodies, given by injection, designed to target the PCSK9 protein that maintains LDL cholesterol in the bloodstream.
They work differently from statins – pills, now available as low-cost generics, that block the liver's production of LDL cholesterol in the first place.
Lower 'bad' LDL cholesterol
Both Amgen and Sanofi/Regeneron have filed for FDA approval of their drugs, based on trials showing that they lower "bad" LDL cholesterol in patients whose cholesterol is not controlled by other drugs, those who cannot tolerate other drugs and people genetically predisposed to high cholesterol.
The FDA is slated to decide on Amgen's application for Repatha by 27 August, while the regulatory deadline for Praluent is 24 July.
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Numerous trials have shown that PCSK9 inhibitors significantly lower levels of LDL in the blood, but investors expect widespread use will hinge on whether the drugs are proven to prevent death, heart attacks and other major cardiovascular events.
Both Amgen and Sanofi/Regeneron do not expect definitive data on cardiovascular outcomes for their drugs until larger trials conclude in 2017.
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