Results of a phase 3 study on the experimental anti-obesity drug taranabant demonstrated significant weight loss with relatively few treatment discontinuations, according to a presentation here at the 16th European Congress on Obesity (ECO). Taranabant, however, carries an appreciable risk of adverse psychiatric and gastrointestinal side effects depending on dosage.
The randomised study of 2,502 obese patients, presented on May 16, took place over 52weeks, noted Joseph Proietto, MD, Sir Edward Dunlop Chair of Medicine, University of Melbourne, Heidelberg, Victoria, Australia.
Part of the cohort received placebo, he explained, while the others received taranabant in doses of 2, 4, or 6 mg.
Early in the trial, Dr. Proietto and colleagues re-randomised the subjects, taking those who had received 6 mg of taranabant to 2 mg or placebo after it was observed that the patients had a higher incidence of adverse psychiatric and gastrointestinal effects without obtaining significantly greater benefit.
The patients in the placebo arm achieved an average weight loss of 2.6 kg. The patients in the 2-mg arm achieved an average weight loss of 6.6 kg. The patients in the 4-mg arm achieved an average weight loss of 8.1 kg.
Approximately 57% of the patients in the 2-mg group achieved a minimum weight loss of 5%, compared with approximately 27% of patients in the placebo group.
There were other positive effects as well. Waist circumferences, for example, shrank an average of 3.1% in the patients receiving placebo, 7% in those receiving 2-mg taranabant and 7.5% in those receiving 4 mg. High-density lipoproteins (commonly known as "good cholesterol") increased, too -- by an average of 7% in the patients receiving placebo, 13.2% in those receiving 2-mg taranabant, and 14.1% in those receiving 4 mg.
At the same time, high proportions of patients suffered adverse effects. In patients who received placebo, 28.5% had gastrointestinal problems, compared with 41.8% in patients who received 2-mg taranabant, and 46.7% in patients who received 4 mg. The gastrointestinal problems included nausea and diarrhoea.
Similarly, 20.4% of patients who received placebo encountered psychiatric problems, compared with 28.3% who received 2-mg taranabant and 40.2% who received 4 mg. The psychiatric problems included depression, anxiety, and irritability.
Nevertheless, there were relatively few discontinuations of the treatment due to the adverse gastrointestinal and psychiatric effects. Discontinuations due to adverse gastrointestinal effects were 0.7 % in the placebo arm, 1.7% in the 2-mg arm, and 2.7% in the 4-mg arm. Discontinuations due to adverse psychiatric effects were 4.6% in the placebo arm, 8.9% in the 2-mg arm, and 12.5% in the 4-mg arm.
"In combination with diet and exercise, treatment with 2 mg of taranabant was generally well tolerated and led to meaningful weight loss and improvements in obese and overweight patients," Dr. Proietto concluded.
Taranabant is known as a cannabinoid-1 receptor (CB1R) blocker.
Source: Doctor's Guide