AstraZeneca should stick to its winning formula. It doesn’t need a $400bn US mega-merger

The Anglo-Swedish drugmaker’s flirtation with a grand combo with US group Bristol Myers Squibb is baffling • AstraZeneca shares fall 8.9% over merger talks with US cancer drug firm Sir Pascal Soriot, chief executive of AstraZeneca, starts with huge credit in the bank, obviously.…