Experimental Drug Slims Obese Monkeys
WEDNESDAY Nov. 9, 2011 -- An experimental drug that targets and kills fat cells in the blood appears to help obese rhesus monkeys lose weight, a new study suggests.
In the future, this approach may help obese humans lose weight, according to the University of Texas M.D. Anderson Cancer Center researchers.
"Targeting blood vessels of white fat tissue is a novel conceptual approach against obesity," said study author Dr. Wadih Arap, the Stringer Professor of Medicine and Experimental Diagnostic Imaging at M.D. Anderson. "Adipotide is a new drug candidate against obesity to be translated into potential clinical applications in humans."
The report was published in the Nov. 9 issue of Science Translational Medicine.
The usual way drugs work to counter obesity is either by suppressing appetite or by increasing metabolism to try to burn calories faster, the investigators noted.
However, this new drug works by attaching itself to fat cells in the blood vessels and triggering a synthetic protein that causes the cell to die. These cells are then reabsorbed and metabolized, the researchers explained.
When the drug was tried on monkeys that were naturally obese they lost about 11 percent of their body weight over a month, Arap's team found.
In addition, the treated monkeys also improved their insulin resistance, which is a marker for developing type 2 diabetes. After treatment, the monkeys used 50 percent less insulin, the researchers found.
"Moreover, the monkeys lost 27 percent of abdominal white fat after Adipotide treatment," Arap said.
When the drug was given to lean monkeys they did not lose weight, suggesting that the drug may just select obese animals.
The drug did not have any adverse side effects, the researchers said, adding that the monkeys were "bright and alert throughout, interacting with caretakers and demonstrating no signs of nausea or food avoidance."
Within a month after treatment was stopped the monkeys started to gain weight again, the study authors noted.
The researchers are planning to test the drug on prostate cancer patients. These patients are prone to weight gain during hormone therapy, which can lead to arthritis-causing inactivity and a host of other health problems.
In addition, fat cells produce growth hormones that help cancer cells thrive, the researchers explained.
In this study, patients would receive injections of adipotide for 28 days.
"There is an increasingly clear scientific and medical interplay among obesity, metabolic syndrome and several human cancers, such as prostate, breast, colon, ovarian, among others," Arap said.
"Basically, we are in a cancer center and our group in particular has long been interested in this matter as a potentially new therapeutic in prostate cancer patients," he said.
Obesity expert Dr. David L. Katz, director of the Prevention Research Center at Yale University School of Medicine, said that "for those hopeful that pharmacotherapy might ultimately help us overcome epidemic obesity, this study serves up a preliminary dose of encouraging news."
This good news comes in a precautionary package of prior experience, Katz noted. "A study of nine weeks in a small group of genetically select monkeys is a very far cry from evidence in people, in the real world, over a meaningful span of time," he said.
Even weight-loss drugs that appeared to perform well in people over time like rimonabant and sibutramine have all led to disappointment, either because of waning effectiveness or toxicity, Katz noted.
"Adipotide may prove an exception to this rule, but believing it now would be the triumph of hope over experience," Katz said.
"This should not distract us from how much good we could reliably get done right now if we focused on turning what we already know about the power of feet and forks into what we routinely do," he added.
For more information on obesity, visit the U.S. National Library of Medicine.
Posted: November 2011