Pfizer biotech drug tops placebo in knee pain trial

Fri Jun 18, 2010 4:30am EDT

* Improves arthritis pain, function at 3 tested doses

* Well-tolerated, but some tissue swelling seen

* Could be first biotech drug for pain

By Bill Berkrot and Ransdell Pierson

NEW YORK, June 18 (Reuters) - A new type of biotech arthritis drug being developed by Pfizer Inc (PFE.N) was significantly better at reducing knee pain than a placebo at all three tested doses in a late-stage trial, according to data presented on Friday.

The drug, tanezumab, which is administered by infusion every eight weeks and works by blocking a protein called nerve growth factor that is associated with pain, could become the first biotechnology drug for pain.

"What we've seen so far in terms of Phase II trials and this first Phase III trial has impressed upon us that this drug has some extraordinary efficacy benefits," said Mark Brown, who is heading up the drug's arthritis clinical development program for Pfizer, and led the study being presented at the European League Against Rheumatism (EULAR) meeting in Rome.

Several injectable biotechnology medicines are used to treat rheumatoid arthritis, a potentially crippling immune system disorder. More traditional oral pain killers are typically used to treat osteoarthritis, which is damage to the joints caused by wear and tear.

"We believe this drug will ultimately prove itself to be superior to exiting therapies for osteoarthritis," Brown said.

Pfizer said tanezumab would not have the high price generally associated with biotech drugs, which can cost tens of thousands of dollars per year.

The 690 patients in the Phase III study were either unwilling or unable to take standard pain killers -- such as NSAIDs like aspirin and ibuprofen, and Pfizer's own Celebrex, a member of a class of drugs called Cox-2 inhibitors. The trial also included patients who did not get sufficient relief from those drugs or those who were candidates for knee surgery.

Patients in the study received tanezumab at doses of either 2.5 milligrams, 5 mg, 10 mg or a placebo.

After 16 weeks, patients in all three tanezumab groups had statistically significant improvement compared with placebo in the primary goals of pain measurement and physical function, Pfizer said.

Pain was rated on a scale of zero to 10, with 10 being most extreme pain. Most of the patients began the trial with a pain rating of about 7.

Those taking the lowest does of tanezumab on average reported pain reduced by 3.15 points, while the 5 mg group had pain cut by 3.26 points and the pain level fell by 3.62 points in the 10 mg group. The placebo patients reported an average drop of 2.42 points.

On a similar zero to 10 physical function measure, the improvement was 2.8 points, 3.02 points and 3.29 points for the three tanezumab doses versus 2.04 on placebo.

"When you see a high degree of pain relief you will see a high improvement in function; they were both equally impressive," Ken Verburg, Pfizer's team leader for the medicine, said in a telephone interview.

Patients were also asked for a general assessment of how they were feeling on a 5-point scale with zero being very good, three representing fair and five very poor.

All groups started the trial at around 3.4, which would be between fair and poor. Those taking the highest dose of tanezumab moved a full point down the scale, with the lower doses coming down 0.83 point and 0.87 point. That compared with a reduction of only 0.51 in the placebo group.

Pfizer is also testing tanezumab against the pain drug naproxen, which is sold under the brand name Aleve, with data expected later this year. It is also being tested against more powerful opioid pain drugs to better prove its clinical worth compared with commonly used arthritis treatments.

Tanezumab was deemed to be generally well-tolerated, Pfizer said. But more patients taking it suffered peripheral edema, or swelling of the limbs, than those who got a placebo.

Brown said the condition was mild to moderate and tended to be temporary and was not necessarily the type of edema associated with heart problems.

"From this study we don't have these concerns," Brown said. (Reporting by Bill Berkrot and Ransdell Pierson, editing by Matthew Lewis)

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