Scientists say the experimental drug might be even more versatile, providing a new tool to help people stop abusing drugs and alcohol, too.

It’s called rimonabant, or Acomplia, and last week researchers reported it could help people not only lose weight but keep it off for two years.

Two studies in March suggest it could fight both obesity and smoking, two of humanity’s biggest killers.

The pharmaceutical firm Sanofi-Aventis plans to seek US federal approval for rimonabant next year.

But researchers say the drug’s benefits may go beyond just smokers and obese people.

“I think it’s going to have a big impact on the treatment of addiction,” said Dr Charles O’Brien, an addiction expert at the University of Pennsylvania and the Philadelphia Veterans Affairs Medical Centre.

Animal studies suggest rimonabant can block the effects of marijuana and fight relapse in alcohol and cocaine abuse, he said.

However no human test results for rimonabant in alcohol abuse have yet been published.

Rimonabant’s versatility traces back to its effects on the brain’s reward system, circuitry that tells you to keep on doing something.

The drug appears to help break the connection between an activity like smoking and the rewarding feeling it causes in the brain.

“We think that the (endocannabinoid) system is over activated by chronic smoking, or perhaps even excessive overeating,” said Dr Robert Anthenelli of the University of Cincinnati College of Medicine and the Cincinnati Veterans Affairs Medical Centre. He’s on the advisory board of Sanofi-Aventis.

Rimonabant blocks the effect of the natural endocannabinoids by keeping them from latching onto the brain cells they normally stimulate, he said.

In smokers, for example, that seems to restore the natural balance of the brain reward circuitry, he said.