Having just completed its acquisition of Cadence, Mallinckrodt is buying the USA's Questcor Pharmaceuticals in a deal valued at an eye-watering $5.60 billion.

Mallinckrodt, which is registered in Ireland but operates out of Missouri, is paying $86.08 a share (in cash and stock), which represents a 27% premium on  Questcor's closing price on April 4. The principal attraction of the deal is the latter's Acthar (corticotropin), which is approved by the US Food and Drug Administration for 19 indications, most of which are associated with autoimmune and inflammatory conditions.

Sales of the gel last year climbed 49.6% to $761.3 million and Mallinckrodt chief executive Mark Trudeau said Acthar is increasingly being employed for a range of serious, difficult-to-treat diseases "where patients often have exhausted other good therapeutic options". He went on to say that "after significant due diligence, we have concluded that Questcor is another ideal strategic fit", following on from the recent $1.3 billion purchase of Cadence.

Mr Trudeau concluded by saying that "we believe we are now well on our way to becoming a leader in the development and commercialisation of specialty therapeutics around the world". The combined company's earnings "will be enhanced from sustainable cost and tax synergies" derived from Mallinckrodt's Irish domicile, the firm added.