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Federal health regulators are revisiting questions about the risk of tumors and heart problems with an experimental diet pill from Arena Pharmaceuticals, which was previously rejected for similar safety concerns.

But documents posted Tuesday suggest the company may have provided the government with enough new information to alleviate those concerns.

The Food and Drug Administration denied approval for Arena's lorcaserin in 2010 after scientists raised concerns about tumors that developed in animals studied with the drug. The company resubmitted the drug with additional data earlier this year, hoping for a better outcome.

FDA reviewers said increased hormone levels likely contributed to noncancerous tumors seen in studies of female rats. But reviewers said the evidence suggests "negligible risk to human subjects."

Questions remain about the drug's effects on heart valves, an issue that frequently plagues weight loss pills. The FDA said pooled results from several studies provided by the company show statistically worrisome levels of heart valve damage.

The agency will ask a panel of advisers Thursday whether Arena has provided enough data to address those and other risks.

The FDA is not required to follow the advice of its advisers, though it usually does.

The quest for a blockbuster weight loss drug has eluded nearly every major pharmaceutical firm over the last four decades.

With U.S. obesity rates nearing 35 percent of the adult population, many doctors say new pharmaceutical treatments are needed. And Wall Street analysts estimate that even a modestly effective drug has blockbuster potential.

But a long line of prescription weight loss offerings have been associated with safety problems, most notably the fen-phen combination, which was linked to heart damage in 1997. The cocktail of phentermine and fenfluramine was a popular weight loss combination prescribed by doctors, though it was never approved by FDA.

Arena is one of three small drugmakers racing to launch the first new prescription diet drug in more than a decade. The FDA has already rejected each of the drugs once and all three companies have resubmitted their products for a second review. Earlier this year, rival Vivus Inc. won a surprising endorsement from an FDA panel for its drug Qnexa, raising expectations for Arena and Orexigen Therapeutics Inc., the third company in the race.

Shares of San Diego-based Arena Pharmaceuticals Inc. rose 44 cents, or 16.2 percent, to $3.16 in afternoon trading.

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