FILE PHOTO: Pfizer Chief Executive Ian Read leaves after appearing at a commons science committee hearing at Portcullis House in London May 14, 2014. REUTERS/Luke MacGregor

(Reuters) - Pfizer Inc PFE.N said on Friday Ian Read will retire as executive chairman at the end of this year, after a four-decade association with the largest U.S. drugmaker that included eight years as chief executive officer.

Company veteran Albert Bourla, who succeeded Read, will assume the additional role of chairman.

Read, 66, helped Pfizer weather patent expirations of several blockbusters, including cholesterol drug Lipitor, through dealmaking, expansion in emerging markets and cost cuts.

The drugmaker has since eschewed large, transformative deals because of confidence in the strength of its pipeline.

In July, Pfizer announced plans to spin off its off-patent branded drugs business and combine it with generic drugmaker Mylan NV MYL.O, a move that will help the company focus on its innovative drugs that generate more profit.

Separately, the drugmaker reported positive data from a late-stage study testing its experimental atopic dermatitis treatment, abrocitinib.

The company’s shares gained 0.6% at $36 in premarket trading.