Royalty Pharma decreased the acceptance threshold for its increased bid with $6.4 billion for Irish drug firm Elan to 50 percent plus one share as it seeks enough support to acquire Elan.

Royalty Pharma increased its cash bid for Elan to $12.50 per share but announced its right to reduce the acceptance threshold from 90 percent.

According to Royalty's chief executive Pablo Legorreta, the U.S. firm believes that the increased bid will provide an attractive financial alternative to shareholders. He added in a statement that they are encouraging Elan shareholders against announced transactions.

The previous bid offered by Royalty was rejected by Elan, leading to the new increased bid from an offer of $11.25.

A buyer of royalty rights on patented drugs, Royalty Pharma said that the efforts of Elan to reinvent itself through a series of acquisitions and debt transactions were hasty and were not conceived.

Elan's board is set to review the new offer but advised shareholders to take no move on the bid.