Pfizer Inc has suspended its clinical trials of the experimental osteoarthritis drug tanezumab effective immediately after finding that a small number of patients taking the medication experienced a worsening of their condition that required joint replacement surgery.
The announcement comes less than a week after Pfizer presented positive data at a European medical meeting, showing that tanezumab significantly reduced knee pain better than a placebo in patients with osteoarthritis.
The current Phase III trial involves 690 patients who suffered from chronic knee pain from osteoarthritis but were unable to take an NSAID or Celebrex (celecoxib), another arthritis medication by Pfizer.
The drug is also being tested as a treatment for cancer pain, interstitial cystitis, chronic low back pain, and diabetic nerve pain. The worsening of condition has not been observed so far in non-osteoarthritis patients taking tanezumab, says Pfizer, so these clinical trials will continue.
Tanzumab is a humanized monoclonal antibody that targets nerve-growth factor, a protein that mediates the pain response to injury. It is administered by infusion every eight weeks. During the phase three studies, the most commonly reported adverse events included abnormal peripheral sensations such as tingling, numbness, and a burning sensation; muscle ache, and pain in the extremities.
The US Food and Drug Administration (FDA) is requesting Pfizer to present its assessments of the adverse events and the potential implications for the other tanezumab clinical programs.
"I don't think it's definitely over for this product, but this is a potential big red flag for some of those other indications," said Morningstar analyst Damien Conover, who added it is often difficult to get pain drugs approved.
"We believe this drug will ultimately prove itself to be superior to existing therapies for osteoarthritis," said Mark Brown, head of the arthritis clinical development program for Pfizer.
"The company is coordinating closely with regulatory authorities and investigators to implement the clinical hold in the osteoarthritis studies and for patients with osteoarthritis in the chronic pain program," added Pfizer spokesman MacKay Jimeson. “Patient safety is a top priority for Pfizer.”
Source: Pfizer Inc
