Powerful new weight-loss drug discovered by accident

A powerful new weight-loss drug originally developed to treat brain diseases is twice as effective as the best existing anti-obesity medicines, research has shown.

Obese patients given the drug tesofensine daily for 24 weeks lost around two stone.

The amount of weight they shed was at least double what could have been achieved with the currently available anti-obesity drugs sibutramine and rimonabant, said experts.

Tesofensine, which suppresses hunger and prevents over-eating, targets neurosignalling chemicals in the brain.

Its potential for fighting obesity was discovered by accident while being tested as a treatment for Parkinson’s and Alzheimer’s disease.

Doctors found that obese patients given the drug began to lose weight.

The new study conducted in Denmark involved 161 obese patients with an average weight of around 16 stone.

The were prescribed varying daily doses of tesofensine, or an inactive placebo, for 24 weeks.

At the end of the trial patients on the two highest 0.5mg and 1.0mg doses of the drug had lost 11.3kg (1.77 stone) and 12.8kg (2.01 stone) of weight respectively.

This was more than twice the weight loss experienced by patients taking sibutramine or rimonabant, marketed as Reductil and Acomplia, said the researchers, writing in an early online edition of 'The Lancet' medical journal.

Tesofensine was around four times more effective than a third drug, orlistat.

The authors, led by Professor Arne Astrup, from the University of Copenhagen, concluded: “This phase II study shows that tesofensine is very effective in producing weight loss in patients over six months.”

Previous studies had shown that over a similar period orlistat helped obese patients lose 2.9kg, sibutramine 4.2kg and rimonabant 4.7kg.

However tesofensine was not without side effects. In patients taking the highest dose, the most common problems were dry mouth, nausea, constipation, irregular bowel movements and insomnia.

For this reason the 0.5mg dose was considered the most promising.

The researchers added: “One should keep in mind that this a study of small size, and the very positive findings cannot be directly compared with those produced by much larger phase III studies on currently approved compounds.

“Our findings need to be confirmed in larger phase III trials, and direct head-to-head comparison with approved weight loss compounds is needed before any conclusion about comparative efficacy is made.”

Obesity expert Professor Steve O’Rahilly, from Cambridge University, said: “If we could treat obesity, like we treat high blood pressure, with safe, effective and affordable drugs this would be an enormous boon to health care. However, to date obesity drugs that have been effective have not been safe, and conversely those that are safer, are relatively ineffective.

“The results with this new drug demonstrate that, over a six month period, it is quite effective. However as the drug is likely to have actions on parts of the brain not involved in weight control, the risk of serious side effects on longer term administration will need to be watched very carefully.”