WASHINGTON May 7 U.S. drug reviewers on Monday
questioned whether the benefits of Pfizer Inc's
experimental treatment for rheumatoid arthritis outweighed its
risks of cancerous cells and infections.
The Food and Drug Administration staff said the drug, called
tofacitinib, appeared to reduce swollen and tender joints during
clinical trials, but questioned the method of analyzing X-rays
to prove the drug worked.
The FDA staff review comes ahead of an advisory panel, which
will vote on whether to recommend the drug on Wednesday. The FDA
will make a final decision in August, taking into account the
Analysts say tofacitinib could be a potential blockbuster
medicine, reviving faith in Pfizer's research prowess if its
benefits are deemed to outweigh its risks.
The FDA staff said the company's method of showing its drug
worked, by analyzing and scoring X-rays, did not always mean the
drug actually slowed down structural damage in people with
rheumatoid arthritis, a potentially crippling condition in which
the body's own immune system attacks the joints.
At the same time, tofacitinib was tied to a higher risk of
malignancies, or cancerous cells that could spread, especially
of lymphoma. The FDA staff said the risk of malignancies may get
worse with higher doses or longer exposure to the drug.
"Substantial evidence to support a salutary effect of
tofacitinib for structural damage progression becomes even more
important in light of the aforementioned malignancy concerns,
particularly since other therapies for (rheumatoid arthritis)
are available that may not have a similar malignancy risk," the
FDA staff said in documents posted online on Monday.
Tofacitinib is one of Pfizer's biggest pipeline hopes and
could become one of the few major new medicines to come from its
own laboratories since impotence treatment Viagra more than a
decade ago. If approved, the likely cheaper pill would compete
with widely used injectable medicines, including Abbott
Laboratories Inc's $8 billion-a-year Humira.