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
"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.
"By inhibiting NGF, we really get a dramatic reduction in pain in patients who have pretty severe osteoarthritis," she said. "It doesn't do anything to the disease, it doesn't hurt your stomach, it doesn't change how you think or make you groggy. This is a real game-changer."
The phase 3 trial is also testing the drug in patients with
cancer pain, interstitial cystitis, chronic low back pain, and
diabetic nerve pain.
Dr. Elaine Tozman, associate professor in the division of
rheumatology and immunology at the University of Miami Miller
School of Medicine, said she doesn't think this new painkiller
would add much to the treatment of osteoarthritis.
"This is really a drug which is for a symptom of osteoarthritis, it's really for pain," she said. "As rheumatologists, most of us are looking for a drug that works on the underlying disease."
Tozman noted that patients with severe osteoarthritis of the
knee usually go on to have a joint replacement.
Some 27 million adults in the United States have osteoarthritis,
with the knee being the most affected joint, according to the U.S.
Centers for Disease Control and Prevention.
The number of people with osteoarthritis of the knee is expected
to rise as baby boomers age and as obesity among Americans
increases, Lane said.
For more on osteoarthritis, visit the
U.S. National Library of Medicine.
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