Novel Drug Provides Significant Pain Relief in Moderate to Severe Osteoarthritis

Barbara Boughton

October 29, 2008

October 29, 2008 (San Francisco, California) — A phase 2 clinical trial of a novel drug called tanezumab has shown that treatment once every 8 weeks significantly reduces pain in patients with moderate to severe osteoarthritis, according to research presented here at the American College of Rheumatology 2008 Annual Scientific Meeting.

In the 16-week trial, tanezumab, given at 5 different doses, reduced walking knee pain by 46% to 62%, compared with 22% for placebo, according to lead researcher Nancy Lane, MD, director and endowed professor at the Aging Center, Medicine and Rheumatology, University of California at Davis Medical Center, in Sacramento.

"Pain therapy for osteoarthritis is truly an unmet medical need, and there are very few effective medications to address it. Currently available medications cause side effects or have the potential to cause drug dependency," Dr. Lane said.

"Our study indicates that tanezumab could be an effective treatment option for patients with moderate to severe osteoarthritis. If we continue to see the same safety and efficacy in a phase 3 trial, it might be one of the agents that make it to the clinic," Dr. Lane said during a press conference. She expects that a phase 3 trial of the medication will begin within a year.

In the phase 2 trial, 444 patients, aged 40 to 78 years, were randomized to tanezumab intravenously administered at 10, 25, 50, 100, or 200 μg/kg on day 1 and day 56 of the study. As well as significant improvement in knee pain, the researchers noted improvement in patients' assessments of their conditions. At weeks 12 and 16, the researchers documented significant improvement in those taking tanezumab in the WOMAC physical function, pain, and stiffness scores, compared with those taking placebo. At week 16, the WOMAC pain score had decreased by 29 to 44 points in the tanezumab groups, compared with 17 points in the placebo group. Likewise, at week 16, WOMAC stiffness score had decreased by 32 to 48 points with tanezumab, compared with 18 points with placebo. At week 16, OMERACT-OARSI responders ranged from 60.8% to 87.5% in the tanezumab group, compared with 49.3% in the placebo group.

Dr. Lane noted that most of the patients involved in the trial had fairly severe pain at baseline, ranging from 62 to 69 on the WOMAC scale. "These were patients who were on their way to joint replacements," she said. Tanezumab was effective in reducing pain at all doses, and the effect was maintained through the course of the study, she said.

Tanezumab is a humanized monoclonal antibody that acts on nerve growth factor, a neurotrophin that is released at sites of injury and inflammation. Despite the efficacy shown during the trial, the drug also caused a significant number of adverse events, especially at higher doses. Treatment-related adverse events occurred in 21% of patients receiving tanezumab. The most common were headache (8.9%), upper respiratory tract infection (7.3%), and paresthesia (6.8%).

"Any neurological problems were transient, and nobody dropped out of the study because of sensation changes," Dr. Lane said.

At the same time, the paresthesia evident in the treatment group shouldn't be dismissed lightly, according to Dr. Lane and those who attended the presentation. "Tanezumab is potentially a very promising drug. But the side effect of paresthesia is a concern," said Grace Lo, MD, assistant. professor of rheumatology at Tufts Medical Center in Boston, Massachusetts, who moderated the session. "We need to understand these adverse events, and they need to be looked at in a larger, longer study," she said.

The study was funded by Pfizer. Dr. Lane is a consultant for Pfizer, Proctor and Gamble, and Rigel Pharmaceuticals. Dr. Lo has disclosed no relevant financial relationships..

American College of Rheumatology (ACR) 2008 Annual Scientific Meeting: Abstract 1989. Presented October 28, 2008.

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