New Therapy May Fight Knee Osteoarthritis Pain

A clinical trial of a novel drug known as tanezumab has shown that treatment once every eight weeks significantly reduces pain in patients with knee osteoarthritis, according to research presented this week at the American College of Rheumatology Annual Scientific Meeting in San Francisco, Calif.

Osteoarthritis is the most common joint disease affecting middle-age and older people. It is characterized by progressive damage to the joint cartilage—the slippery material at the end of long bones—and causes changes in the structures around the joint. These changes can include fluid accumulation, bony overgrowth, and loosening and weakness of muscles and tendons, all of which may limit movement and cause pain and swelling.

The weight-bearing joints including the knees, hips and spine are most often affected by osteoarthritis. Osteoarthritis in the knee and hip areas can cause chronic pain or discomfort during standing or walking.

Researchers recently set out to determine if tanezumab, a humanized monoclonal antibody specific for nerve growth factor, is effective in relieving the pain of those with moderate to severe knee OA. They followed 444 men and women who ranged in age from 40 to 78 and had moderate to severe pain associated with their knee OA. Patients enrolled had not had successful control of their pain by nonsteroidal anti-inflammatory drugs, such as ibuprofen or naproxen, or were considered candidates for more invasive treatments such as total joint replacement.

The 444 patients enrolled in this 16 week study were treated with either tanezumab or placebo. Tanezumab was intravenously administered at ten, 25, 50, 100, or 200 µg/kg on days one and 56 of the study. Researchers measured effectiveness by evaluating knee pain with walking and patient global assessment of response to the treatment, as well as other outcome measures, including stiffness and physical function.

Researchers found that tanezumab treatment significantly improved knee pain and the patients’ overall assessments of their condition when compared with placebo over the time of the study. At weeks 12 and 16, researchers noted a significant improvement in the secondary outcome measures, including pain, physical function and stiffness.

Treatment related adverse events occurred in 21 percent of patients receiving tanezumab and in 8 percent of those receiving placebo. Among the patients receiving tanezumab, the most common adverse events among patients receiving tanezumab were headache, upper respiratory tract infection and abnormal tingling sensations.

“Effective treatment to relieve pain in patients with osteoarthritis is an unmet medical need,” says Nancy E. Lane, MD; director and endowed professor, University of California at Davis Medical Center, Aging Center, Medicine and Rheumatology, Sacramento, Calif. “Recent work has found that nerve growth factors are synthesized at sites of inflammation and appear to accentuate pain. Treatment with a monoclonal antibody against nerve growth factor, tanezomab, was very effective in reducing knee pain and improving physical function in patients with moderate to severe knee OA. Therefore, inhibition of nerve growth factor may provide a new type of therapy to reduce pain in OA and possibly other pain states,” explains Dr. Lane. Phase III studies are now being initiated to further define the effectiveness of this medication.