Still, the findings could help smooth the way for regulatory approval, wider use of the drugs by doctors and possibly reimbursement by insurers.

The drugs, evolocumab from Amgen and alirocumab from Sanofi and Regeneron, inhibit a protein in the body called PCSK9 that helps regulate cholesterol. In the studies detailed on Sunday, both drugs reduced the bad cholesterol by about 60 percent, to about 50 milligrams per deciliter from about 120 at the start of the studies. In many cases such big reductions were achieved even though the patients were already taking statins.

Both drugs could win approval from the Food and Drug Administration by this summer. Analysts say the drugs will have billions of dollars in annual sales and will be taken by millions of people who cannot lower their cholesterol enough using statins alone or cannot tolerate statins. (However, the PCSK9 drugs are taken by injection every two weeks or four weeks, which could deter some users.)

Statins reduce cardiovascular risk and scientists believe it is because they decrease low-density lipoprotein, or LDL, the so-called bad cholesterol. But merely looking at cholesterol levels can be misleading. The drug niacin did not protect against heart attacks and strokes even though it raised so-called good cholesterol and modestly lowered bad cholesterol.

Insurers in particular might demand proof that the PCSK9 drugs stave off heart attacks, strokes, deaths from coronary disease and procedures to open arteries before agreeing to pay for them for many patients. Executives at CVS Health, a leading pharmacy benefits manager, recently said that PCSK9 inhibitors might cost $7,000 to $12,000 a year and would strain health care budgets because so many people might use them.

“Managed care pharmacy, indeed the health care system, has never seen a challenge like this to our resilience in absorbing costs,” they wrote in the Health Affairs blog.

Whether the results from these two small studies will be persuasive enough remains to be seen.

The study of Amgen’s evolocumab involved 4,465 patients with various degrees of risk, two-thirds of whom were randomly chosen to get the drug in addition to the medication they were already taking. After one year, 0.95 percent of those in the group that received the drug had suffered a heart attack, stroke or other cardiovascular problem, compared with 2.18 percent in the group that did not take the drug. By a measure known as the hazard ratio, the risk of cardiovascular events was reduced by 53 percent.