People with osteoarthritis (OA) often live with pain that reaches into every part of their lives. Medications currently on the market don’t work in everyone, and many come with side effects that can be dangerous. For instance drugs such as NSAIDs only alleviate about 30 percent of the pain, leaving some treatment options for osteoarthritis (OA) inadequate. NSAIDs and opioids also bring the risk of serious side effects, such as ulcers, heart and kidney problems, or drowsiness and risk of addiction with opioids.

As of March 2012, researchers were investigating new ways to treat OA using biologic medications similar to those used in treating rheumatoid arthritis. One class of drugs called anti-NGFs attack chronic pain by preventing pain signals from reaching the brain. Anti-NGFs are being tested for many conditions such as nerve damage from diabetes, cancer pain and OA.

One of the anti-NGFs being studied is called tanezumab, an antibody designed to specifically block nerve growth factor (NGF), which acts as a master control switch for pain. NGF helps nerve cells grow and divide. In some circumstances though, NGF stops being such a good guy. For example, in the inflammatory environment of an arthritic joint, NGF turns neighborhood bully by goading nearby immune cells into overreacting to inflammation.

Such an action keeps pain messages going to the brain until pain turns chronic and can’t be easily stopped.  

Tanezumab and similar drugs work by blocking NGF in the same way that anti-tumor necrosis factor therapies block pathways that lead to inflammation in rheumatoid arthritis.

“It’s the pathway itself that’s critical,” says Nancy Lane, MD, an arthritis expert at University of California-Davis, and part of a group of researchers who have been studying tanezumab. “The idea is to get more pain relief without side effects,” she says.

In 2010, however, the U.S. Food and Drug administration (FDA) asked Pfizer Inc. (tanezumab’s manufacturer) and other manufacturers of anti-NGFs to suspend clinical studies for OA, lower back pain and for nerve damage from diabetes. The request was made after participants in a Phase III osteoarthritis trial experienced joint failure. Some of those affected required hip replacement surgery.

Dr. Lane and others are hoping that tanezumab and its therapeutic cousins get a second chance. Because anti-NGF therapies work so specifically to block pain the side effects are few and the drug seems to be safe, she says.

On March 12, 2012, the FDA Arthritis Advisory Committee heard testimony from a panel of arthritis and pharmaceutical experts who discussed the risk of anti-NGFs when compared to the benefit of pain relief, and recommended that the FDA resume trials.