Founded in 1992 by a Yale physician, Alexion had struggled for years before its breakthrough came in securing approval of Soliris, a $500,000-a-year rare blood disorder medicine. Alexion's shares have since underperformed on the Nasdaq index, down 40 per cent since its 2015 peak, and under Ludwig Hantson, the chief executive, it has been emerging from a period of boardroom upheaval a few years ago and criticism of misfiring acquisitions. Underlining the American company's problems, Elliot, the formidable US activist investor, put pressure on Alexion's board in May to pursue a sale.