Randall Osborne of Elsevier's “Pink Sheet Daily” contributed to this report.
Pharmaceutical manufacturer Merck & Co. has stopped developing taranabant, a weight-loss drug, because of concerns over psychiatric side effects, the company announced last month.
“Available phase III data showed that both efficacy and adverse events were dose related, with greater efficacy and more adverse events in the higher doses,” Dr. John Amatruda, senior vice president and research head, diabetes and obesity, at Merck Research Laboratories, said in a statement.
Interim results presented at the European Congress on Obesity in Geneva earlier this year from a 2-year study of taranabant in more than 1,200 overweight and obese patients showed average losses of 5.7 pounds, 14.5 pounds, and almost 18 pounds in patients who received placebo, taranabant 2 mg, and taranabant 4 mg, respectively.
However, psychiatric adverse events occurred in 20% of those on placebo, 28% of those on taranabant 2 mg, and 40% of those on taranabant 4 mg.
The company's decision “represents a major setback in the future development of agents for obesity,” Dr. Yehuda Handelsman, director of medical education management at the Metabolic Institute of America, in Tarzana, Calif., said in an interview. “The message drug companies got from the FDA is that they should not waste their money to study drugs for obesity and related diseases if they have some side effects, because the agency will not approve such drugs.”
Merck's decision to abandon taranabant is only the most recent in a series of setbacks for the cannabinoid-1 (CB-1) receptor antagonist class of obesity drugs. Last year, an FDA advisory panel recommended against approval of Sanofi-Aventis's CB-1 antagonist rimonabant (Zimulti); the company withdrew its new drug application for rimonabant a few weeks later.
But Sanofi is not completely through with rimonabant. A phase III trial of the drug, marketed in Europe as Acomplia, is expected to report data in the second half of 2009.
Pfizer's CP-945598, another CB-1 antagonist for obesity, also seems to be on its way out. Results from a 2,000-patient phase III trial were expected in the first quarter of 2009, but Pfizer recently said obesity programs will be dropped.
One CB-1 antagonist that is still being investigated is Bristol-Myers Squibb/ Solvay's CB-1 antagonist SLV-319. That compound is currently the subject of phase IIb trials.
Dr. Handelsman is on the speakers bureau for Merck & Co. and has received research support from Sanofi-Aventis.