The ALN-PCS injection can be given as an alternative for the one in five people who cannot take statins - the current gold-standard cholesterol-lowering drugs.
But, in what marks a revolutionary new treatment option, the drug could be given in combination with a statin to produce even greater effects at cutting the artery-clogging fats.
Professor Peter Weissberg, the British Heart Foundation's medical director, said that people with extremely high cholesterol are at increased risk of a heart attack, and this approach could offer hope for those who are resistant to statins.
He said that these results add to growing evidence that blocking the action of a certain protein can dramatically lower 'bad' LDL cholesterol.
More research is now needed to confirm this approach is both safe and effective at preventing heart attacks in the long term before it becomes widely available, he said.
The results are published in The Lancet.