Royalty Pharma says that it wants to buy Elan Corp. PLC for about $6.5 billion, but has yet to receive a response from the Irish drug maker.
The $11 per share offer, which was made earlier this month and applies to both Elan's regular and American depository shares, represents a 4 percent premium over its Friday closing ADS price.
The news disclosed Monday sent Elan's U.S. shares up 80 cents, or 7.6 percent, to $11.40 in premarket trading on Monday.
Royalty Pharma, a private company based in New York, acquires royalty interests in marketed and late-stage biopharmaceutical products. It does not discover, develop or market products.
The company said Monday that Elan hadn't formerly responded to its proposal and that it's been unsuccessful in engaging the company in talks since the proposal was made.
Elan officials in Ireland didn't immediately return a call seeking comment.
Royalty Pharma said it plans to finance the acquisition through a combination of cash and debt.
Over the past 52 weeks, Elan's U.S. shares have traded between $9.37 and $15.27. Over the past year, the shares have lost about 15 percent of their value.