Two drugs -- interferon-alpha 2b and ribavirin -- that are commonly used together against hepatitis C inhibited the spread of the MERS coronavirus in the rhesus macaques species, they said.
The combination also braked inflammation and reduced the risk of pneumonia in treated animals, they said.
The combination "should be considered as an early intervention therapy" given the lack of targeted treatment or vaccine for MERS, they wrote in the journal Nature Medicine.
A cousin to the SARS virus that erupted in China a decade ago, causing a global health scare, Middle East Respiratory Syndrome (MERS) causes flu-like symptoms, with fever and respiratory difficulties, but can also lead to organ failure.
According to a toll placed on the World Health Organisation (WHO) website on August 30, the virus has killed 50 out of 108 known cases of infection.
Last week, Qatar and Saudi Arabia said three more fatalities had occurred. It was not immediately clear whether these were included in the 108 cases recorded by the UN's health agency.
The research, led by Heinz Feldmann of the US National Institutes of Health (NIH), entailed infecting six monkeys with the virus.
Three were given shots of the drugs very soon -- just eight hours -- after infection, which was followed up with additional doses at regular intervals over three days.
The three other monkeys were left untreated, to serve as a comparison.
The animals were then killed, and their bodies examined to measure levels of virus and damage to tissues.
Work on the primates proceeded after researchers found that the drugs inhibited the MERS virus in lab-dish cells.
The researchers admit to limitations in their work.
The rhesus macaque is the only known animal substitute for humans in experiments on MERS.
However, it tends to develop only mild or moderate forms of the disease.
As a result, the doctors are unsure whether the combination treatment is an option for people with severe MERS.
On the other hand, it may be possible to treat humans later than was the case in the animal experiments, they say.
"The prolonged disease course in humans suggests the treatment window may be considerably longer," says the paper.