BRUSSELS (Reuters) - U.S. drugmaker Pfizer (>> Pfizer Inc.) gained European Union antitrust approval on Tuesday for its proposed $15 billion acquisition of U.S. rival Hospira (>> Hospira, Inc.) after pledging to sell some drugs to allay competition concerns.

"The approval is conditional on Pfizer divesting certain sterile injectable drugs, as well as its infliximab biosimilar drug, which is currently under development," the European Commission said.

The deal, the biggest ever for Pfizer, will boost its portfolio of generic injectable drugs and copies of biotech medicines.

(Reporting by Julia Fioretti and Foo Yun Chee)

Stocks treated in this article : Pfizer Inc., Hospira, Inc.