While Sanofi’s diet drug Rimonabant (Acomplia / Zimulti) remains stalled at the FDA, a potential competitor currently in phase III trials, Merck’s MK-0364, now has an official generic name: Taranabant.

Taranabant is Merck’s cannabinoid-1 (CB-1) receptor inverse agonist, and from reports we periodically receive from participants in the phase III trial of this diet drug, taranabant is as effective for weight loss as rimonabant with fewer side effects.

An experimental weight loss medication in the same class as the drug Acomplia helped patients lose weight in a 12-week, phase II study, but side effects were common at higher doses.

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.

Taranabant Trial

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 diet and 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 most.

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 new diet pill, if approved, won’t be for everyone. “This is not going to be a class of drugs that people take because they want to look good on vacation” and lose 10 pounds or so.