Biogen, the $75 billion biotech giant, is surging after a report that it has received takeover interest.
The Wall Street Journal on Tuesday reported that Merck and Allergan have each expressed interest in doing a deal.
The talk of a takeover comes just days after Biogen said its CEO George Scangos would leave the company after six years at its helm.
A takeover of Biogen would be the biggest of a biotech company since 2008, and one of the largest takeovers on record by a drug company.
Biogen, based in Cambridge, Massachusetts, focuses on neurological and autoimmune diseases.
Drugmakers embarked on a record dealmaking spree in 2014 and 2015, as they sought to rebuild drug pipelines as older drugs lost patent protection.
Several of the largest biotech takeovers of those years became fiercely competitive as huge drugmakers tapped low-cost debt for the spending.
A spokesperson for Allergan said the company "does not comment on market rumor or speculation." Merck and Biogen could not immediately be reached for comment.