The number of monkeys was minimal, treatment was started very soon after infection, and drugs that work in monkeys sometimes fail in humans, he said, adding: “But if I were a doctor with MERS patients, and I had nothing else to give them, I wouldn’t hesitate. If someone has advanced disease, there’s 50 percent mortality.”

Dr. Ziad A. Memish, the deputy health minister of Saudi Arabia, where most of the known MERS cases have occurred, said doctors there had already tried the two-drug combination on patients. It did not work well, he said, but that might have been because it was started late, when patients were hospitalized and already severely ill.

“This is great news and much-needed information, although it’s very preliminary,” he said.

Saudi doctors tried the regimen, Dr. Memish added, because of a recent article in the International Journal of Infectious Diseases reviewing therapies that seemed to help during the 2003 global epidemic of SARS, which is also caused by a coronavirus.

According to the World Health Organization, there have been 108 known human cases of MERS since it emerged in 2012, of which 50 have been fatal.

There is no recommended treatment, although patients are often put on ventilators and given corticosteroids to fight inflammation in their lungs and other supportive therapy.