Coronary artery bypass graft surgery. (iStock)

People taking statins for heart disease saw major benefits when doctors added a powerful, newer drug to their treatment regimen, according to a major study released Friday morning at the start of an American College of Cardiology conference in Washington.

The addition of the cholesterol-busting drug evolocumab, from a class known as PCSK9 inhibitors, reduced the risk of deaths, heart attacks, strokes, the need for coronary bypass and hospitalization for chest pain, according to a team of researchers from around the globe, who also published their results online Friday in the New England Journal of Medicine.

Evolocumab works by lowering LDL, or “bad,” cholesterol. The researchers found an average decline of 59 percent in LDL levels among the 14,000 people in 49 countries who were put on the drug for 48 weeks, when compared with an almost identical number of patients who received a placebo.

And when the researchers looked at the most serious possible outcomes for heart patients — deaths, heart attacks and strokes — the study showed a 20 percent reduction of those events.

“The data from our trial provide insight into the benefit of decreasing LDL cholesterol levels to median levels lower than those in previous trials,” wrote the researchers, led by Marc S. Sabatine of Brigham and Women’s Hospital in Boston.

The data reinforce the growing body of evidence showing that as clinicians push LDL cholesterol levels ever lower, their patients fare better. Currently, an LDL cholesterol below 100 is considered optimal for people at risk of heart disease, according to the Mayo clinic.

Heart disease is the number one killer of Americans.

A second study of another PCSK9 inhibitor, bococizumab, was much less successful and was terminated, another set of researchers reported Friday. It showed widely varying effects on LDL cholesterol levels and had no benefit for people with LDL levels below 100, although patients with higher LDL levels did see significant benefits. In contrast to evolocumab, the impact seemed to fade with time and some patients developed antibodies to the drug.

Pfizer, the drug's manufacturer, halted development of bococizumab in November. A third drug is still under study.

The evolocumab study was funded by Amgen, the pharmaceutical company that makes the drug, which is marketed as Repatha. Amgen announced in February that the drug was a success, but details of the research were not released until Friday.

The Food and Drug Administration approved the first PCSK9 inhibitors in 2015, but only for people with heterozygous familial hypercholesterolemia, an inherited disorder that can severely elevate LDL levels, or for patients who have had heart attacks and other serious cardiovascular problems but still cannot reach target LDL levels using statins.

In the study released Friday, the impact of the drug actually grew over time. At a news conference, Sabatine said that the reduction in the most serious harms was 19 percent in the first year and 33 percent in the second year. That increasing impact over time is similar to the effect of statins.

"It takes time for LDL lowering to translate into healthier arteries," he said.

Taken by injection, PCSK9 inhibitors cost about $10,000 a year, far more than statins, which are now available in generic form and are in millions of home medicine cabinets around the world. But some people cannot take them without significant side effects, such as muscle pain, and in most people they do not lower LDL cholesterol as significantly as the new drugs.

The average age of the patients in the study was 63, and three-quarters of them were men. More than 80 percent had suffered heart attacks, and some had histories of stroke and peripheral artery disease. Nearly all were taking modest or large doses of statins.

The main note of caution expressed by other experts Friday concerned the cost of the drug. Sabatine said cost-benefit analyses will have to be conducted before the FDA and the medical community can determine how widely the drugs will be used. He said the main criteria for him would be an analysis of the patient's baseline risk and those most likely to see the largest reduction in LDL cholesterol.

"As a class, these drugs clearly have the potential to lower event rates," said Paul M. Ridker, director of the Center for Cardiovascular Disease Prevention at Brigham and Women's hospital, who presented the bococizumab study and spoke at the news conference. "Now the question is who do you give them to."