New Drug Attacks Fat, Helps Obese Monkeys Slim Down

Scientists have developed a new drug that attacks excess body fat, and a new study reports that it helped a small group of obese monkeys lose weight. Experts say the drug's fat-attack mechanism is an intriguing approach to weight loss, but questions remain about the drug's effectiveness and safety in humans.

Previous diet drugs try to help the body lose fat by increasing metabolism or by controlling the hunger pangs that make people want to eat more. But researchers at the M.D. Anderson Cancer Center in Houston designed the new drug Adipotide to attack the fat itself by destroying the blood supply that keeps it alive.

"Without the blood supply, the fat withers away and is remetabolized by the liver," said Dr. Wadih Arap, one of the study's authors.

The researchers tested the drug in a small group of obese monkeys. After four weeks, the monkeys lost an average of 11 percent of their body weight. The drug also lowered the animals' Body Mass Index (BMI) and trimmed their waistlines. Lean monkeys who took the drug did not lose weight, suggesting that the drug selectively targeted the fat in obese monkeys.

The study was published in the journal Science Translational Medicine.

"This is an exciting new concept in our efforts to control obesity," said Dr. Lou Aronne, director of the Comprehensive Weight Control program at Weill-Cornell Medical College. "But we need human studies for efficacy and more importantly, safety."

Researchers say the fact that the drug worked in monkeys, the closest animal relatives of humans, makes them hopeful that the drug could be safe and effective in humans. The monkeys in the study were also similar to people in the way they packed on the pounds – by overeating and not exercising.

But despite the promise of these early results, the drug seems to share some of the problems that have plagued diet drugs and "magic bullet" obesity treatments in the past. Four weeks after the monkeys stopped taking the drug, they began to regain their weight. Dr. Keith Ayoob, associate professor in pediatrics in the Albert Einstein College of Medicine in Bronx, N.Y., said that fact makes the drug like many of its less-than-magical predecessors.

"We've always been able to get people to lose weight, but the real question is how to keep the lost weight from returning. Right now, there's no drug for that," Ayoob said.

Arap acknowledged that the drug didn't seem to help the monkeys keep weight off, but he noted that the animals didn't change their lifestyles or diet the way that humans can.

"The hope is that in patients, we say this treatment gave you a leg up and helped you lose the weight, now you have to diet and exercise and change your lifestyle," Arap said.

Even if Adipotide proves to be successful in humans, the drug would have to travel the long regulatory road required by the U.S. Food and Drug Administration before it could be sold for weight loss. Experts have noted that the agency's approval process seems to be more rigorous for drugs aiming to fight obesity. The FDA nixed three weight-loss drugs submitted for approval in 2010, citing safety concerns.

Currently, only one drug is FDA-approved for weight loss: orlistat (sold as Xenical or Alli). But the drug causes a number of unpleasant and damaging side effects, including liver damage, pancreatitis and kidney stones, according to a report from the consumer watchdog Public Citizen in April.

Adipotide produced some side effects in the monkeys in this current study, particularly in the kidneys. But the researchers noted that these were "generally mild and reversible."