If Alexion failed to offer more aggressive financial performance guidance or consider strategic alternatives such as a sale, Elliott could start a proxy fight to claim board seats, the paper reported, citing people who were not authorized to speak publicly.

In a recent meeting between Alexion and Elliott, the hedge fund sought to have more biotech experts as directors and suggested four potential candidates, the newspaper said.

"Alexion believes in active and constructive dialogue with all of our shareholders, and we value their perspective," a company spokeswoman said in an emailed statement on Friday.

The hedge fund has set an end-December deadline for the board changes, according to the report.

Alexion has made "significant progress executing an aggressive and decisive strategy", the spokeswoman said.

In September, the company said it would lay off about 20 percent of its workforce.

The company has been hit by a sales-practices scandal related to Soliris, its pricey rare-disease treatment, as well as an exodus of top management including its chief executive and chief financial officers who left late last year.

Elliott started investing in Alexion in April and has warned the company against ambitious acquisitions beyond its core expertise, according to the report.

(Reporting by Kanishka Singh and Ankur Banerjee in Bengaluru; Editing by Gopakumar Warrier and Sriraj Kalluvila)