A long-acting cholesterol medicine cut the risk of having a heart attack or some other serious problems by 15 to 20 percent in a big study that’s likely to spur fresh debate about what drugs should cost.

Statins such as Lipitor are cheap and cut cholesterol, but some people don’t get enough help from them. The new drug, Amgen’s Repatha, lowers cholesterol more and is given as shots every two weeks or once a month.

It costs $14,000 a year, and insurers have balked at paying without proof that it lowers heart risks. The new study gives that evidence, but the benefit is not as great as some doctors had hoped.

Results were discussed Friday at a medical conference and published by the New England Journal of Medicine.