Twenty years ago, the fight against cancer seemed as if it were about to take a dramatic turn.

Traditionally, cancer doctors fought the disease with crude weapons, often simply poisoning fast-growing cells whether they were cancerous or healthy. But then a team of researchers hit on a new strategy: drugs targeting proteins produced by cancer cells that seemed necessary to their survival.

One such drug, Gleevec, worked spectacularly in patients with chronic myeloid leukemia. But the clinical trials that followed mostly have produced disappointments. According to a study published earlier this year, only 3 percent of cancer drugs tested in clinical trials between 2000 and 2015 have been approved to treat patients.

A study published on Wednesday in the journal Science Translational Medicine offers one reason for the failure: Scientists are going after the wrong targets.

“I hope people will really wake up to the need to be much more rigorous,” said Dr. William Kaelin, a professor of medicine at Harvard University who was not involved in the new study.