EON

Arena Pharmaceutical stock fell by over 20 percent Monday on news that its obesity drug has underperformed in clinical trials. The experimental drug lorcaserin has achieved the primary endpoints of the study, and Arena reports it is well tolerated by patients.

This paves the way for approval by the Food and Drug Administration, enabling it to be sold in the United States. However, weight loss goals were not reached, causing investors to back off and Arena’s stock price to fall. Patients taking the drug for over a year lost only 5.8 percent of their body weight versus 2.2 percent for those on a placebo.

The company had expected a 5 percent difference for those using the drug. Analysts predict low sales for the drug even if approved by the FDA since its clinical studies show results that be achieved by intense dieting.

Obesity drugs are under scrutny due to safety concerns.

Major manufacturers such as Merck and Pfizer have recently discontinued work on these drugs due to clinical evidence that they can contribute to depression and suicidal thoughts. Lorcaserin reportedly did not display these side effects or the heart valve damage which is another concern for this class of drug.