There was good news and bad news Friday for people at very high risk of heart attack or stroke.

The good news: A study in the New England Journal of Medicine found the people taking a newer kind of cholesterol-lowering drug cut their risk of heart attack, stroke, hospitalization for chest pain, cardiac death, and other cardiovascular events by 15 percent.

Previous studies had shown that the medication—evolocumab (Repatha)—could slash levels of LDL (bad) cholesterol to below 30, well under the 100 that is usually considered ideal. But this is the first study to show that those dramatic reductions translated into health benefits.  

The bad news: The drug—which is taken once a month, as an injection—costs over $1,000 a month, probably has to be taken indefinitely, and insurers still may not cover it. That's because that 15 percent reduction isn't substantial enough to make the drug cost effective, Peter Bach, M.D., director of the Center for Health Policy and Outcomes at Memorial Sloan-Kettering, wrote on Twitter Friday afternoon. In addition, while the drug did prevent deaths from heart disease, it did not reduce deaths overall.

While patients in the study did not report many side effects, some experts worry that, over time, lowering your LDL level so much could impair the body's ability to absorb fat-soluble vitamins and possibly impair cognitive function, wrote Robin P.F. Dullart, M.D., from the department of Endocrinology, University of Groningen, in the Netherlands, in an editorial accompanying the new Repatha study.

And it's important to remember that Repatha is only approved for a narrow slice of people: Those with a genetic condition that causes extremely high LDL levels, and those who have already had a heart attack or stroke and can’t get their LDL levels down despite serious efforts to make lifestyle changes plus maximum doses of statins, such as atorvastatin (Lipitor).

Heart experts had high expectations for Repatha, and a related drug called alirocumab (Praluent). Both belong to a new type of medication, called PCSK9 inhibitors, that work differently than statins. So they offered hope to the small group of people not sufficiently helped by those older medications.

"This is a game changer for high-risk patients," Sean E. Harper, M.D., executive vice president of research and development at Amgen, the maker of Repatha, said in a press release.

In an effort to encourage insurers to cover the drug, Amgen has offered to refund the cost of medication if patients suffer a heart attack or stroke.

And both Amgen and Sanofi, the maker of Praluent, have told us in the past that us that they have programs that can lower out-of-pocket costs for some people who are not on Medicare or Medicaid.