In a widely expected move, U.S. regulators rejected Merck & Co. Inc.'s arthritis drug Arcoxia amid concerns that it could pose some of the same cardiovascular risks as the company's withdrawn pain reliever Vioxx.

The Food and Drug Administration said it wanted more data showing that the benefits outweighed potential risks before approving Merck's successor drug to Vioxx, the company said today.

Merck said the FDA issued a "nonapprovable" letter for Arcoxia stating that "Merck would need to provide additional data in support of the benefit-to-risk profile for the proposed doses of Arcoxia in order to gain approval."

The FDA's decision was anticipated after an FDA advisory panel voted 20-1 two weeks ago against approval of Arcoxia to treat osteoarthritis because of a possible link to increased risks of heart attacks and strokes.

Arcoxia is a pain reliever in the same class of drugs, called cox-2 inhibitors, as Vioxx, which Merck pulled off the market in September 2004.

"We are disappointed with today's decision," said Peter S. Kim, president of Merck Research Laboratories, based in West Point. "We pursued FDA approval of Arcoxia because we believe strongly that new medicines are needed for patients whose osteoarthritis pain is inadequately managed with currently available therapies."

Arcoxia is on the market in 63 other countries, and Merck said it would continue selling the drug outside the United States. Arcoxia had sales of $265 million last year.

Merck did not say whether it would reapply with additional data. "At this time, we are evaluating the FDA's letter," company spokesman Ron Rogers said.

Kim told shareholders at Merck's annual meeting this week that the company was committed to working with the FDA to get Arcoxia on the U.S. market.

Kim said in a statement today that "there is more long-term safety data from controlled clinical trials" for Arcoxia than for any other cox-2 drugs and traditional anti-inflammatory medicines.

"I think they will conduct the additional studies and resubmit at some future point," Herman Saftlas, an analyst at Standard & Poor's, said in a telephone interview. "That's my gut feeling. I don't think they will just throw away this drug. It's being sold extensively overseas."

Arcoxia, like other cox-2 inhibitor drugs, was developed to avoid ulcers and gastrointestinal problems of older nonsteroidal anti-inflammatory drugs, or NSAIDs, such as ibuprofen and naproxen.

Merck had been awaiting approval of Arcoxia since December 2003, and asked the FDA to approve 30- and 60-milligram doses.

But Arcoxia came under increased scrutiny after Merck withdrew Vioxx in September 2004 following analysis of studies confirming increased risks of heart attacks and strokes. Vioxx generated nearly $2 billion for Merck in 2003.

Only one cox-2 inhibitor, Celebrex, made by Pfizer Inc., is still sold in the United States. In 2005, Pfizer pulled its other cox-2 drug, Bextra, off the market at the FDA's request and strengthened warnings on Celebrex.

The FDA advisers who met April 12 said Arcoxia's risk of causing heart attacks and strokes appeared to outweigh its marginal advantage of relieving pain with fewer minor stomach problems - and likely at a much higher price than existing drugs.

Panel members did agree that Arcoxia might benefit some patients. But they noted that Merck gave them no estimates of the number of patients or scope of what it called an unmet need.

Many Wall Street analysts had expressed doubt that the FDA would approve Arcoxia, and had not factored new Arcoxia revenue into their projections for Merck, which is based in Whitehouse Station, N.J., and employs 12,000 outside Philadelphia in West Point, Upper Gwynedd, Blue Bell and Wayne.

Merck shares closed down 57 cents, or 1 percent, at $51.86 today on the New York Stock Exchange.

Contact staff writer Linda Loyd at 215-854-2831 or lloyd@phillynews.com.