New Potential Drug for Osteoarthritis

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.

"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.