Experts said the findings were the most important since the first statins trials two decades ago. On the other hand, researchers didn't observe any effect on the rates of hospitalization for unstable angina, cardiovascular death or hospitalization for worsening heart failure, or death from any cause.
What the study hasn't yet proven is that people were less likely to die while on the drug.
The results of a large worldwide trial on 27,000 patients paved the way for the drug to become available to millions of people.
"This is one of the most important trials of cholesterol-lowering since the first statin trial, published 20 years ago", said Professor Peter Sever, from the National Heart and Lung institute at Imperial, who led the United Kingdom arm of the trial involving 1,500 patients across 75 centers.
It means that if all 325,000 eligible Britons were to be treated, 2,200 potentially fatal heart emergencies would be avoided every year.
The results of the study, which cost about $1 billion and was paid for by Amgen, maker of the drug, were published on Friday in The New England Journal of Medicine and presented at the annual meeting of the American College of Cardiology.
The drug was designed for people already taking the maximum dose of cholesterol-lowering statins but who had been unable to lower their cholesterol level sufficiently to ward off heart disease, in some cases because of an inherited genetic condition.
Separately, Repatha cut heart attacks by 27 per cent and stroke by 21 per cent.
Repatha, injected either once or twice a month, lowered LDL by about 60 per cent to a median of 30, with a quarter of patients getting below 20, researchers reported. In the second year of the study, the results were more pronounced, with a 35 per cent reduction in heart attack risk and a 24 per cent decrease in stroke risk. The benefits were seen across all subtypes of patients, even in those who started with low levels of cholesterol.
"What this trial shows is that if you achieve these really low levels of cholesterol, you get the additional benefit, and you get that without any apparent adverse effects".
Heart disease and stroke are the number one killers worldwide, taking 15 million lives in 2015, according to the World Health Organization.
Last May NHS watchdog NICE approved Repatha and a similar drug called Praluent on the basis of early trials.
The drug, Repatha, is called a PCSK9 inhibitor and can make cholesterol tumble to levels nearly never seen naturally in adults, or even in people taking cholesterol-lowering statins.
The treatments were approved only for specific groups - those with a genetic condition which means they have dangerously high cholesterol, and people with heart disease who can not cope with the side effects of statins. "Why not just reduce the price of the drug and make it more broadly available?"
Price could provide a stumbling block however. Due to its steep pricing, most medical insurances do not want to pay for the drug. A similar drug to Repatha, called Praluent, costs about as much.
Reacting to the offer, multiple doctors were mostly critical about the deal, stating that it may be a lose-lose situation for both the patient and their insurance provider.
However, new drug evolocumab changes the way the liver works to also cut bad cholesterol.
Professor Sir Nilesh Samani, medical director at the British Heart Foundation, said the trial was a "significant advance".
The study demonstrated that the effect of Repatha on the primary endpoint of executive function was non-inferior to placebo.