WEDNESDAY, Sept. 29 (HealthDay News) -- A new painkilling drug called tanezumab appears effective in relieving knee pain from osteoarthritis, researchers are reporting.
But the U.S. Food and Drug Administration has halted a phase 3 trial of the drug after 16 patients developed worsened arthritis and underwent joint replacements.
Lead researcher Dr. Nancy E. Lane, director of the Aging Center, Medicine and Rheumatology at the University of California, Davis, said those patients who ended up needing a knee replacement most likely overworked their damaged joint because they were feeling no pain.
"They probably accelerated the degeneration of the joint," she said. "Sometimes, pain is good in protecting you."
The study findings were published in the Sept. 30 issue of the New England Journal of Medicine.
Tanezumab is made by Pfizer Inc., which funded the trial. Whether the osteoarthritis portion of the phase 3 trial will resume is up in the air. Pfizer spokesman Mackay Jimeson said the company is still in discussions with the FDA, and no decisions about the drug's future have been made.
For the study, Lane's team randomly assigned 450 patients with osteoarthritis of the knee to receive either tanezumab or a placebo. Those taking tanezumab had their pain reduced anywhere from 45 percent to 62 percent, compared with those given a placebo, who saw their pain reduced 22 percent, on average.
Lane said tanezumab, which is given by injection, should probably not be used frequently. The effect of the drug can last at least eight weeks, she added, but no studies have been done yet on its long-term effects.
The drug works in a unique way by blocking nerve growth factor (NGF), which is essential for normal development of the nervous system, but is also released when there is inflammation. NGF stimulates nerve cells and triggers pain, Lane explained.
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