Last Updated: 2008-01-15 15:16:18 -0400 (Reuters Health)
By Karla Gale
NEW YORK (Reuters Health) - Taranabant is a new drug that induces weight loss by reducing appetite and increasing the amount of calories burned, according to new data published in the medical journal Cell Metabolism.
Using PET scanning, the study showed that taranabant entered the brain and bound to about 30 percent of the central nervous system receptors, Dr. Steven B. Heymsfield at Merck Research Laboratories in Rahway, New Jersey, told Reuters Health.
"This is the first drug study to show these relations in humans," he pointed out, which are important in developing dosing and understanding the side effects.
Taranabant is also believed to work outside the small area of the brain "known to have important body weight regulatory effects," he added. These new drug actions "provide new therapeutic opportunities for weight management given the very limited current repertoire of weight-loss drugs."
In a weight loss study designed to find the optimal dose, taranabant induced significant weight loss in obese subjects, the authors report. The study was completed by 368 of the original 533 subjects who were randomly assigned to receive placebo or taranabant up to 6 milligrams (mg) per day.
The average weight losses from the beginning of treatment to week 12 ranged from 1.4 kilograms (3.1 pounds) in the placebo group to 3.6 kg (7.9 lb) in the group receiving 0.5 mg taranabant and 6.4 kg (13.9 lb) in subjects taking 6 mg taranabant.
Gastrointestinal adverse events and psychiatric symptoms were common, causing 32 subjects to discontinue treatment.
In a 24-hour food intake study that included 36 overweight and moderately obese participants, the total calories were reduced significantly in 22 percent in subjects who were randomly assigned to 12 mg taranabant compared with those in the placebo group.
In another study involving 17 overweight or moderately obese subjects, resting energy expenditure was measured. (Resting energy expenditure is the amount of calories the body requires during a non-active period of 24-hours.)
Between 2 and 5 hours after dosing, the average ratio of peak resting energy expenditure after treatment with 12 mg of taranabant and 30 mg of sibutramine (another weight-loss drug) was almost the same. Heymsfield's group also observed a statistically significant decrease in average respiratory quotient after 12 mg taranabant "suggesting increased fat metabolism."
"Such modest increases in energy expenditure, particularly when combined with appetite suppression, could exert profound effects on body weight over a period of months," the research team concludes.
"Our study is one of the first and definitely the most comprehensive" to evaluate the drug's effect on food intake and energy expenditure in overweight patients, Heymsfield said. "More studies in this area are needed."
SOURCE: Cell Metabolism, January 2008.
Dr. Sears comments:
This drug is the cousin of rimonbant that inhibits the binding of endocannaboids to their receptors in the brain. This decreases hunger so you lose weight. The results of the two drugs are virtually the same. Rimonbant was denied FDA approval because of its neurological side effects. I imagine this new drug will have the same side effects if not greater. The best way to reduce endocannaboid binding in the brain is high-dose fish oil. Its only side effect is to make you smarter.