Jeremy Laurance
July 20 2004 at 10:29AM
When British scientists announced they had developed a drug that could potentially cure obesity two years ago, it created excitement around the world.
Researchers raced to check claims that a drug based on a hormone in the body could promote weight loss by cutting food intake by a third.
Headlines spoke of a cure for the "third helping" after the head of the laboratory that made the discovery, Professor Stephen Bloom of Imperial College, London and the Hammersmith Hospital described how the drug PYY3-36 curbed hunger by telling the appetite centre in the brain when the stomach was full.
At least two drug companies took up the chase and millions of rands have been spent in experiments on the drug.
Now the "breakthrough" may have turned out to be an apparition.
Professor Bloom's research has been questioned by more than 40 scientists from 15 international research centres who report they have been unable to replicate his findings.
The dispute revolves around the race to create an obesity wonder drug, one of the most important - and potentially lucrative - quests in medicine.
Professor Bloom and his colleagues have spent more than 20 years studying the causes of obesity and the hormones that control appetite.
When his team published claims in 2002 that the hormone decreased food intake and caused weight loss in mice and rats, Professor Bloom announced that they had found the "hormone for satiety". An infusion of the hormone given to human volunteers curbed their appetite for 12 hours so that when tempted with a buffet they consumed a third fewer calories than volunteers given a placebo infusion.
Speaking at the time, Professor Bloom said "more than a billion people" across the world were "extremely overweight" and a solution to the problem was vital. "It may be possible to identify foods which cause the release of more PYY3-36, helping to naturally limit appetite, or it may be possible to create a tablet with similar effect providing an excellent, natural and safe long-term treatment for obesity," he said.
But then the problems began.
A group of 42 scientists from leading obesity research institutions and universities across Europe and America tried to the replicate the findings in rodents.
Now they say their failure to do so "calls into question" the potential value of an anti-obesity approach based on the administration of PYY3-36.
The group, led by Matthias Tschop of the University of Cincinnati, says the original aim of repeating Professor Bloom's experiments was to accelerate the development of a new treatment for obesity.
Like Professor Bloom, the group injected PYY3-36 into the bodies of young rats. But they found the rats ate no less than the control group injected with salt solution.
Yet Professor Bloom's group had reported a decrease in weight gain of about 20 percent.
When the academic found other researchers were having similar difficulty replicating Imperial College's experiments, they decided to collaborate. They bought rats from the same source as Professor Bloom, bought food from the same supplier, and injected the animals at the same time of day with the same kind of syringes filled with PYY3-36 made by the same chemical supply house.
"The results we generated were entirely unexpected. We have been unable to replicate their results," Dr Tschop said.
Professor Bloom maintained his experiments had been replicated many times by his own group and even by two outside drug companies. He pointed out that his research had come under attack in the past and had later been proved correct. "Our results are completely convincing. It's not a problem replicating the work, it's a question of doing it properly. Handling the laboratory rats and mice during the experiments can cause stress which can put the animals off their food and so interfere with the action of PYY3-36."
The dispute is important because many hundreds of scientists around the world are now working on PYY3-36 in the belief that there is conclusive evidence that it works on both rodents and humans who took part in small-scale trials. - The London Independent