About ReutersPossible carcinogen found in Pfizer AIDS drug
Tue Sep 11, 2007

WASHINGTON (Reuters) - A potential human carcinogen has been found in
batches of Pfizer Inc.'s AIDS drug Viracept, U.S. regulators said on
Monday.

Levels of the substance, ethyl methanesulfonate or EMS, were "substantially
lower" than those that prompted Roche Holding AG to recall the same drug in
Europe, a Pfizer letter to physicians said.

A Food and Drug Administration notice called EMS a "potential human
carcinogen." Studies suggest EMS may cause cancer and birth defects in
animals but no data in humans exist, the FDA and Pfizer said.

The agency and Pfizer agreed that pregnant women and children who are
starting HIV therapy should not be given Viracept until further notice, the
letter said.

Pediatric patients who are stable on Viracept-containing regimens may
continue to be treated with the drug, the letter said.

Pregnant women currently taking Viracept should be switched to an
alternative medicine while manufacturing changes are implemented to limit
EMS levels, the letter added.

For pregnant women with no alternative treatment options, "FDA and Pfizer
agree that the risk-benefit ratio remains favorable for the continued use
of Viracept," the letter said.

A Pfizer spokeswoman could not immediately be reached for comment.

Pfizer shares were off 1.1 percent, or 26 cents, to $23.99 in afternoon
trading on the New York Stock Exchange.

© Reuters 2007.