* Tanezumab osteoarthritis trials halted immediately
* Some patients worsened, needed joint replacement
* FDA requested trials suspension
* Pfizer shares down 0.8 percent
(Adds analyst, Pfizer comment, background)
By Bill Berkrot
NEW YORK, June 23 (Reuters) - Pfizer Inc said it suspended clinical trials of its experimental biotech arthritis drug, tanezumab, at the request of U.S. health regulators after some patients taking the medicine experienced a worsening of their condition that required joint replacement surgery.
The worldwide suspension of the clinical osteoarthritis program is effective immediately, Pfizer Inc (PFE.N) said on Wednesday.
The announcement was the latest in a long list of setbacks for the world’s biggest drugmaker, which has been stung by criticism it has been unable to develop important new medicines on its own, despite an annual research and development budget in excess of $7 billion.
The clinical hold includes both suspension of recruitment of new patients and of the dosing of existing patients in the osteoarthritis program, as well as patients with osteoarthritis in other tanezumab studies, Pfizer said.
The halt comes less than a week after Pfizer presented positive tanezumab data at a European medical meeting showing it significantly reduced knee pain better than a placebo in patients with osteoarthritis.
Tanezumab, which is administered by infusion every eight weeks and works by blocking a protein called nerve growth factor that is associated with pain, has the potential to become the first biotechnology drug specifically for pain.
Several injectable biotechnology medicines are used to treat rheumatoid arthritis, a potentially crippling immune system disorder. More traditional oral pain killers, such as aspirin, ibuprofen and Pfizer’s own Celebrex, are typically used to treat osteoarthritis, which is damage to the joints caused by wear and tear.
The worsening seen in a small number of osteoarthritis patients leading to surgery has so far not been observed in non-osteoarthritis patients taking tanezumab, Pfizer said.
The U.S. Food and Drug Administration, which requested the arthritis trials program halt, has asked Pfizer to present its assessment of the potential implications of the adverse events for the other tanezumab clinical programs.
The drug is also being tested as a treatment for cancer pain, interstitial cystitis, chronic low back pain and diabetic nerve pain.
“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.
Pfizer is trying to produce lucrative new drugs that can help replace lost revenue when its $12 billion a year cholesterol fighter Lipitor goes off patent late next year. Branded drugs quickly lose 80 percent or more of their sales once faced with competition from cheap generics.
The company bought smaller rival Wyeth for $67 billion last year in large part to gain control of its vaccines and promising pipeline of drugs in development as a hedge against the loss of Lipitor revenue.
Pfizer executives had expressed excitement about tanezumab’s potential only last week.
“We believe this drug will ultimately prove itself to be superior to existing therapies for osteoarthritis,” Mark Brown, who is heading up the drug’s arthritis clinical development program for Pfizer and presented the data last week, had said in a telephone interview.
Pfizer said it is working with the FDA to determine the appropriate course of action for the drug going forward.
“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,” Pfizer spokesman MacKay Jimeson said.
Pfizer shares were down less than 1 percent to $14.75 in extended trading from their New York Stock Exchange close at $14.88. (Reporting by Bill Berkrot; editing by Carol Bishopric and Andre Grenon)