FDA panel supports continued testing of pain drugs

A panel of arthritis experts recommended Monday that the federal government allow continued testing of an experimental class of pain drugs for arthritis, despite links to bone decay and joint failure

The Food and Drug Administration's 21-member panel of arthritis experts voted unanimously that research on the nerve-blocking drugs should continue, with certain safety precautions. Reports of joint failure led the agency to halt studies of the drugs in 2010 before any of the medications could be submitted for U.S. approval.

Pfizer Inc., Johnson & Johnson and Regeneron Pharmaceuticals have asked the FDA to lift the moratorium on testing of their drugs. The FDA will weigh the advice of its panel before making a final decision.

"There's clearly a worrisome safety signal, but in spite of that, I think there's an unmet need in certain patient populations," said panelist Dr. Sherine Gabriel, of the Mayo Medical School in Rochester, Minn.

Panelists noted that not all patients respond to medications currently on the market, like Aleve and aspirin. The experts also said that the drugs could prove useful in treating a variety of other chronic pain conditions for which there are few options.

"Anything that has the hope of helping pain patients is worth pursuing," said Susan Broyles, the patient representative on the panel.

Drugmakers have touted the drugs, known as nerve growth factor inhibitors, as a potential breakthrough for treating osteoarthritis, back pain and other chronic pain conditions. They've pointed to strong results in early testing and shortcomings of familiar painkillers like aspirin and Advil, as well as powerful opiate-based drugs. Anti-inflammatory painkillers like Advil can cause stomach bleeding, while opiates carry a high risk of addiction

The injectable nerve-silencing drugs offer a new approach, by blocking proteins that control pain sensations throughout the body.

Experts said more study is needed to determine why some patients taking the drugs saw their arthritis worsen, in some cases to the point of joint failure. One industry theory is that patients become more active after their pain subsides, leading to increased damage at their most problematic joints.

Data analyses by the FDA showed a higher rate of joint problems among patients taking nerve-inhibitors and anti-inflammatory drugs at the same time. However, there were also cases of bone deterioration in patients taking the newer drugs alone.

The FDA's panel said the new drugs should not be mixed with older medications in future studies. Additionally, patients should be warned of the safety risks in a detailed informed consent waiver. The drugmakers should also take X-ray and MRI images to track the strength of patients' bones throughout the trial.

Problems with nerve growth factor inhibitors first emerged in the summer of 2010, when the FDA asked Pfizer to halt studies of its experimental injection tanezumab in patients with osteoarthritis, low back pain and diabetic nerve pain. The action came after Pfizer researchers reported that osteoarthritis actually worsened in certain patients, requiring joint replacements in some cases.

In December that year the FDA put a research hold on all drugs in the class after similar problems emerged, halting studies by Johnson & Johnson and Regeneron Pharmaceuticals Inc. Regeneron was developing a compound called REGN475, in cooperation with Sanofi-Aventis. Johnson & Johnson was testing its drug fulranumab in several pain conditions. The FDA lifted its hold on a trial of the drug for cancer pain last summer, though studies for osteoarthritis remain on hold.

Associated Press