Orexigen has since been mum on further progress, other than to say last month that it was continuing with the dispute resolution process.
New Look at Crucial Lorcaserin Rat Study
Arena's lorcaserin was tripped up by data showing an increase in rat mammary tumors coupled with clinical efficacy results showing a mean average weight loss of 5 percent, the poorest of the three products. The FDA indicated that the drug's tepid efficacy failed to offset the safety risks.
The company has now produced a reanalysis of the two-year rat study, commissioning a group of independent pathologists to take another look at the tumor diagnoses.
The result: "Adenocarcinomas were no longer numerically higher than the control group in the lorcaserin low- and mid-dose groups," Arena said in a statement.
Another potential cancer risk mentioned by the FDA was astrocytoma, also seen in rat studies, though not in the drug's clinical trials. Arena has addressed this problem indirectly, with pharmacokinetic data indicating that the drug penetrates into the human brain at far lower rates than in rats.
As a result, the company suggested, lorcaserin concentrations in the human brain are probably much lower than rats at equivalent doses.
On the other hand, recently reported efficacy data for lorcaserin have confirmed that it seldom produces large weight loss. For example, a meta-analysis of three phase III trials reported in June, based on intention to treat, found that more than one-third of patients failed to lose 5 percent of body weight after one year and only about one-fifth lost 10 percent or more.
Arena has not said when it plans to ask the FDA to reconsider approving the drug.