FILE PHOTO: A sign marks a Biogen facility in Cambridge, Massachusetts, U.S. January 26, 2017. REUTERS/Brian Snyder/File Photo

(Reuters) - Biogen Inc said on Monday it would buy back shares worth $5 billion, days after its stock slumped on the drugmaker’s announcement to end two Alzheimer’s disease trials.

Biogen had lost more than $18 billion of its value last week after the company and partner Eisai Co Ltd ended two late-stage trials of their experimental Alzheimer’s disease treatment, aducanumab.

Biogen shares, which lost 32.4 percent of their value since the company’s announcement on Thursday to scrap the trials, were up 1.5 percent before the opening bell on Monday.

The share buyback is in addition to the approximately $1.7 billion remaining under the stock repurchase program authorized by its board in August 2018, the company said in a regulatory filing bit.ly/2Tt6APq.