Pfizer halts osteoarthritis trial

Based on a request from the US Food and Drug Administration (FDA), Pfizer has suspended its global phase III clinical trials programme testing the investigational painkiller tanezumab in osteoarthritis. The FDA's request was based on a small number of reports of osteoarthritis worsening in subjects taking the drug, sometimes even leading to the need for joint replacement.

The adverse event has not been observed in tanezumab patients in clinical programmes for other indications, the company noted. However, at the FDA's request, Pfizer will meet with the agency this week "to present its assessment of the potential implications of the adverse events in the osteoarthritis programme for the other tanezumab clinical programmes."

The programmes include ongoing studies in patients with cancer pain, interstitial cystitis, chronic low back pain and diabetic peripheral neuropathy.

The clinical hold, which is effective immediately, suspends the recruitment of new osteoarthritis patients and the dosing of existing osteoarthritis subjects, as well as dosing of patients with osteoarthritis in other studies.

Tanezumab is a humanised monoclonal antibody directed against nerve growth factor. It was acquired by Pfizer when the company bought the biotech firm Rinat in 2006.

The announcement of the suspension of the tanezumab programme comes directly on the heels of other negative safety-related news for Pfizer. Earlier this week, the company said it would withdraw its cancer drug Mylotarg (gemtuzumab ozogamicin) from the US at the request of the FDA after postmarketing data found that the drug, which was approved based on surrogate endpoints under the FDA's accelerated approval programme, was not as safe or effective as it appeared to be in pre-marketing studies.