The challenge was to find that compound and ensure that it would be safe for humans to take as a drug. There were many claims to success, but none held up.

Dr. Vagelos, who had just begun a job as head of research at Merck, suggested that Mr. Alberts take on the task.

Almost immediately, Dr. Vagelos learned that Merck had a competitor. Dr. Akira Endo of the Japanese drug company Daiichi Sankyo had already found such a compound, and his company had tested it in the laboratory and in dogs and was starting tests in people.

“I said, ‘Oh, my God, we are behind already,’” Dr. Vagelos recalled. “Then I said: ‘The hell with it. We are a lot faster than they are. Let’s go ahead.’”

Soon Mr. Alberts found a similar compound secreted by aspergillus, a fungus. The compound, he found, proved effective in the laboratory and in animal studies, so Merck began tests in people, and it did exactly what it was supposed to — reduce levels of LDL cholesterol, the dangerous kind.

Suddenly Daiichi Sankyo stopped all tests of its compound. The company would not say why, but the rumor was that it was causing tumors in dogs.

That did not bode well for Merck.

“Their compound was an inhibitor of HMG-CoA reductase,” Dr. Vagelos said. “Ours was an inhibitor of the same enzyme. If the rumor was true, that it was causing tumors in dogs, the implication was that it would cause cancer in humans. We could not put humans at risk. I decided we would stop all studies.”