Arena Pharmaceuticals Inc said on Saturday U.S. health officials have rejected its experimental obesity pill, citing cancer risks.

The drugmaker said Food and Drug Administration officials requested an independent review of the findings and may require additional studies to assess risks to humans from tumors found in animal studies.

The FDA found the risks outweighed the “marginal” effectiveness of the drug.

Arena had hoped its drug, called lorcaserin, would be the first new U.S. prescription weight-loss drug in more than a decade in a sector battered by serious side effects.

But investors’ hopes for the drug sank after FDA’s outside advisers last month urged the agency to reject the pill amid worries that tumors in rats given the drug might indicate a risk of cancer in humans.

Shares of Arena have fallen 56 percent since the panel’s recommendation, and analysts have largely expected the agency to reject the weight-loss drug since the panel voted last month.

Saturday’s announcement is the latest in a string of bad news for U.S. diet drugs.

Abbott Laboratories’ controversial Meridia was pulled off the market earlier this month, leaving few alternatives. FDA panelists in July also rejected a potential rival from Vivus Inc. The FDA’s final decision is due on Thursday.

Some of the concerns about lorcaserin could be addressed by data expected from a 600-patient company trial next year, said Piper Jaffray analysts Edward Tenthoff and Chad Messer.

“We envision Arena will need to conduct additional clinical and preclinical studies ... and project a push out of potential lorcaserin approval by at least three years,” they said on Wednesday, adding that approval could come in 2015.

One last experimental weight loss drug has yet to face FDA’s advisers - Orexigen Therapeutics Inc makes its case for Contrave Dec. 7.

Japan’s Eisai Co Ltd holds U.S. marketing rights to lorcaserin.

Arena held a conference call on Monday to address the FDA’s decision. Arena Chief Executive Jack Lief said in a statement the company intended to meet with the FDA to “obtain further clarity on the approval path and timeline.”

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WASHINGTON/NEW YORK (Reuters)