The FDA Decides Not to Approve Arena’s Weight Loss Drug Lorqess

Following on the heels of the decision for Bydureon, the FDA also decided last week not to approve Arena Pharmaceutical’s new weight loss drug Lorqess (lorcaserin). But this move by the FDA was less surprising. The FDA’s primary concern with this weight loss drug was the development of tumors (including mammary [breast tissue] tumors and astrocytomas [brain tumors]) in mice and rats treated with the drug. Given that the drug demonstrated relatively low efficacy in its phase 3 clinical trials – between 3.0% and 3.7% weight loss after one year with the highest doses tested – the potential risks outweighed the potential benefits of the drug, in the FDA’s view. The FDA has asked Arena to conduct additional laboratory experiments to learn about the tumor promoting mechanism(s) of lorcaserin in rats, and to provide clear evidence that such risks do not exist in humans. If this cannot be done in the laboratory, a two-year cancer study in animal models and/or additional clinical trials would likely be required. Although Arena has indicated that it plans to conduct the laboratory studies, no concrete timeline on when these studies would be carried out and when the drug would likely be resubmitted to the FDA for approval have been disclosed yet. We would be interested to know how the top 10% of patients on the drug did; we understand 3-4% weight loss isn’t necessarily considered significant but we are curious about, in addition to those who did “average,” how did the best patients do?  --BK