The U.S. Food and Drug Administration told J&J last week that the development program for its drug fulranumab had been put on hold, Jeffrey Leebaw, a spokesman for New Brunswick, New Jersey-based J&J, said in an e-mail. London-based AstraZeneca said yesterday it has voluntarily stopped early-stage research of a similar medicine. Regeneron Pharmaceuticals Inc. of Tarrytown, New York, said yesterday the FDA had halted trials of its treatment in the class known as anti-nerve growth factors.

Pfizer Inc., the world’s largest drugmaker, suspended trials of the pain drug tanezumab in June after reports that patients in one of its studies needed joint replacements. The move left nerve-growth inhibitors “a tainted class” and has lowered investor’s expectations, said Ziad Bakri, a Cowen & Co. analyst in New York.

“You’d have to have a lot of safety data to ever get a drug like this approved, so for investors this is not a class that’s generating very high hopes,” Bakri said in a telephone interview. “You’re not going to see many companies chasing these drugs at this point.”

Before New York-based Pfizer halted its trials at the FDA’s request, tanezumab and similar nerve-growth treatments were estimated to reach as much as $11 billion in annual sales, Catherine Arnold, a Credit Suisse analyst in New York, wrote in a May 3 note to investors.

J&J, Pfizer

J&J rose 9 cents to $62.02 in New York Stock Exchange composite trading at 9:35 a.m., after falling 3.9 percent for the year before today. Pfizer was unchanged at $17.49 and has fallen 3.9 percent for the year. Regeneron slipped 31 cents, or 1 percent, to $33.38 in Nasdaq Stock Market composite trading and has gained 39 percent this year.

In light of the Pfizer findings, AstraZeneca stopped studies on its nerve inhibitor, medi578, Janet Milton-Edwards, a company spokeswoman, said by telephone. The suspension wasn’t requested by regulators and the company hasn’t seen similar cases of bone-tissue death, she said. AstraZeneca is “evaluating how we will go forward” with the research, she said.

AstraZeneca rose 14 pence to 2,988 pence on Dec. 24, the most recent day of London trading.

FDA Concerns

The FDA said it was concerned that J&J’s fulranumab and other drugs in the class may be associated with rapidly progressive osteoarthritis, a wearing away of the cartilage protecting bone joints, or osteonecrosis, the death of bone tissue due to a lack of blood supply, according to Leebaw, the company spokesman.

J&J isn’t aware of trial results until researchers release data, so the company doesn’t know how many side effects have occurred, if any, he said.

The company “will work with the FDA toward resolution of this issue,” he said. J&J didn’t notify investors of the suspension because it is “not a material event for us,” he said.

Pfizer’s tanezumab may have increased joint problems in some people because it worked too well, reducing the pain that could have signaled to patients that they were overusing fragile bones, researchers said in a study published on Sept. 29 in the New England Journal of Medicine. Sixteen of 6,800 patients taking the medicine needed replacements in knee, hip or shoulder joints, the study found.

Regeneron on Hold

Regeneron said in a regulatory filing today that the agency halted study of its anti-nerve growth factor, REGN475/SAR164877, after confirming last week a case of avascular necrosis, or bone-tissue damage, in the trial of another company’s treatment. Regeneron didn’t name the other company or drug involved. The biotechnology company is developing its treatment with Paris- based Sanofi-Aventis SA.

There are currently no ongoing trials with the Regeneron drug that are enrolling or treating patients, the company said in the filing.

Avascular necrosis occurs when bones don’t get enough oxygen and nutrient-carrying blood, according to the website of the Rochester, Minnesota-based Mayo Clinic.

Pfizer’s development program remains on hold, MacKay Jimeson, a spokesman, said by telephone. Pfizer is preparing a response and studying data from 15 studies with tanezumab, Jimeson said. He declined to comment on Regeneron’s statement.

Abbott Laboratories, which is studying another nerve-growth inhibitor, hasn’t been contacted by the FDA and has seen no cases of avascular necrosis, said Tracy Sorrentino, a spokeswoman for the Abbott Park, Illinois-based drugmaker. The study of the drug, ABT-110, is “proceeding as planned,” she said yesterday in a telephone interview.

Peter Dworkin, a Regeneron spokesman, didn’t respond to messages seeking comment. Shelly Burgess, an FDA spokeswoman, said the agency couldn’t comment beyond confirming research suspensions already disclosed by companies.