New Weight Loss Drug Shows Promise
Modest Weight Loss Seen in Some Patients Taking Taranabant
Jan. 8, 2008 -- An experimental
weight loss medication in the same class as the drug Acomplia helped
weight in a 12-week, phase II study, but side effects were common at higher
Like Acomplia (rimonabant), which is approved for sale in Europe but not in
the U.S., the Merck & Co. drug taranabant targets receptors in the brain
linked to appetite.
Concerns about reports of
depression in rimonabant users have kept the drug off the market in the
Based on these reports, an FDA advisory panel voted against recommending its
approval last June, prompting manufacturer Sanofi-Aventis to withdraw its
application to the agency.
Depression and anxiety were also reported in the taranabant study, but these
side effects were most common at the highest doses given, researcher Steven
Heymsfield, MD, of Merck Research Laboratories, tells WebMD.
Based on these findings, an ongoing phase III trial of taranabant does not
include the highest doses used in phase II study.
The double-blind study included 533
obese people randomly assigned to treatment with either placebo or 0.5
milligrams, 2 milligrams, 4 milligrams, or 6 milligrams of taranabant. All the
participants received counseling on
exercise throughout the trial.
At the end of 12 weeks, the placebo-treated participants had lost the least
weight and those treated with the highest dose of taranabant had lost the
Patients treated with 0.5 milligrams of the drug lost an average of 3.5
pounds, compared with 5 pounds among people treated with 2 milligrams of the
drug and almost 9 pounds among those treated with 6 milligrams.
A total of 27% of patients who took 0.5 milligrams of taranabant lost 5% or
more of their body weight, compared with 61% in the 6-milligram group.
But patients taking the higher dosages of the drug also had higher rates of
side effects, including anxiety,
nausea, and vomiting.
The study drop-out rate due to side effects was also twice as high among
patients treated with the highest dosage of the drug, compared with the lowest
dose (10.2% vs. 4.7%). But no patients dropped out because of serious
The study appears in the January issue of the journal Cell
Heymsfield says he was surprised to find that patients treated with the
lowest dose of the drug lost weight.
"We didn't expect weight loss at all doses," he says.
Seeking FDA Approval
The ongoing phase III trial includes roughly 2,000 people being treated with
taranabant at doses ranging from 0.5 milligrams to 2 milligrams, a Merck
spokeswoman tells WebMD.
She adds that the plan is to petition the FDA for approval in the second
half of this year if the phase III results prove promising.