A new nonopioid pain reliever could be welcome news for people who have difficult-to-treat back pain.
Tanezumab is what's called a monoclonal antibody. And it might offer extended relief from chronic lower back pain, a large, new study finds. However, a serious side effect remains a concern.
Tanezumab works differently from other treatments, as it blocks nerve growth factor, a protein that causes pain, researchers say.
"It appears that we are on the cusp of developing new drugs, which treat chronic pain by turning down the sensitivity of the nervous system, which is a whole new way of approaching the problem of chronic pain," said lead researcher Dr. John Markman. He's a professor of neurosurgery and neurology at the University of Rochester School of Medicine in New York.
"This is very important because we haven't really had drugs with a new way of affecting chronic pain developed in maybe 100 years," Markman said.
This phase 3 trial was funded by drugmakers Pfizer and Eli Lilly and Co. Twelve-hundred patients were randomly assigned to one of two doses of tanezumab or placebo. Another 600 patients received the opioid tramadol.
The higher dose of tanezumab reduced pain and also improved function, the researchers said.
Currently, opioid painkillers or nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin and ibuprofen are the only medications for chronic lower back pain. But opioids can be addictive, and NSAIDs can cause serious gastrointestinal bleeding.
If these drugs don't work, the alternative is spinal fusion surgery, and that's not always effective, Markman said.
Tanezumab is given by injection about every two months. It has none of the side effects of opioids or NSAIDs.
It does, however, have one very serious side effect that affects up to more than 2% of patients. The drug has been linked to joint deterioration that may require joint replacement.
This concern is the major focus of the U.S. Food and Drug Administration's current review of the drug as a treatment for chronic pain from severe osteoarthritis, Markman said.
The current study was done in 191 sites in eight countries in North America, Europe and Asia. It involved patients who did not get pain relief after trying at least three different pain drugs, including opioids.
Patients underwent treatment for a little over a year. At four months, patients taking 10 milligrams of tanezumab reported significantly more pain relief than those using the placebo.
Also, after four months, more patients taking the experimental drug reported pain relief than those taking tramadol.
Markman said the drug "is very promising and really represents a step forward."
Lower back pain affects 80% of Americans, and in as many as 20% of cases can become chronic and debilitating and disruptive, said Dr. Yili Huang, director of pain management at Northwell Health Phelps Hospital in Sleepy Hollow, N.Y.
"Any potentially effective new treatment is truly exciting," said Huang, who was not involved in the study.
Many of the currently available treatments for chronic lower back pain act on the same anti-inflammatory or opioid receptors, he said. "Treating a new target along the pain pathway can open the door to potentially safer and more effective treatments," Huang noted.
Medical treatment of lower back pain is becoming increasingly challenging as many medications may have dangerous long-term side effects that can lead to cardiovascular disease, addiction, and kidney and liver disease, Huang said.
"The efficacy of tanezumab in treating pain in patients who have already failed treatment with these medications, including opioids, is very encouraging, but we must not discount the very small chance of it causing potentially devastating serious joint problems," he said.
"Like all treatments, we must weigh the risks and benefits before proceeding, but it is a welcome addition to the treatment toolbox," Huang added.
Because the drug doesn't yet have FDA approval, Markman said it's too early to estimate the cost. But like most new drugs, he said it will likely be expensive.
The report was published online June 19 in the journal Pain.
For more on lower back pain, visit the U.S. National Institute of Neurological Disorders and Stroke.