In the latest chapter of the battle for control of Elan Corp, the Irish drugmaker has rejected a third increased offer from Royalty Pharma but noted that it has hired an advisor to look at other offers.

At the end of last week, Royalty raised its bid to potentially $8 billion. Specifically, it offered $13 per share, up from $12.50, plus an additional $2.50 per share in contingent value rights. The latter would depend on the performance of Tysabri (natalizumab), the multiple sclerosis drug that Elan sold its stake in to partner Biogen Idec in return for $3.25 billion and royalties.

Elan has yet again turned down Royalty's offer, saying that "the value gap…remains significant", adding that the bid is "wholly inadequate". However, "in response to several recent unsolicited enquires", the company has instructed Citigroup to "assess any or all tangible indications of interest that would reflect a proper valuation of the overall business platform".

The Elan board says it remains unanimous in recommending "four previously announced transactions" that will be voted on at an upcoming extraordinary general meeting to be held on June 17. Those deals include a $1 billion alliance giving it access to royalties from Theravance's four respiratory drugs partnered with GlaxoSmithKline and the acquisition of Austria's AOP Orphan Pharmaceuticals.