Pfizer replaces long-time CEO Ian Read with veteran Albert Bourla

US drugmaker Pfizer on Monday announced that chief executive Ian Read is stepping down, handing off to chief operating officer Albert Bourla on January 1.

Read will serve in future as executive chairman of Pfizer's board of directors, the company said in a statement.

"It's been an honour to serve as Pfizer's CEO for the past eight years," Read said in the statement.

"However, now is the right time for a leadership change, and Albert is the right person to guide Pfizer through the coming era." Pfizer, one of the world's biggest drugs companies, reported earnings of $3.9 billion in the second quarter, up 26 per cent from the year-ago period.

But like its rivals, Pfizer is contending with the expiry of patents on some of its blockbuster drugs, which has allowed generic drugmakers to offer cheaper alternatives.

This evolution had hit earnings to the tune of $23 billion during Read's time at the top, Pfizer said in its statement announcing the leadership change.

But it said a strong pipeline of new products bequeathed by the outgoing CEO meant "the company is now better positioned for success".

Bourla, 56, became chief operating officer at the start of this year after previously overseeing Pfizer's "Innovative Health" unit.

He said he was "humbled and privileged" to be unanimously appointed by the board as Read's successor.

"This is a dynamic time for Pfizer, and I look forward to working with our colleagues to deliver critical medicines to patients all over the globe, which remains the compass for all we do at Pfizer," he said.