U.S. drugmaker Pfizer (PFE) fought back on Saturday against criticism that its planned takeover of rival AstraZeneca (AZN.L) would damage Britain’s science base by saying strong UK research was a key reason for the deal. Given its record of big job cuts after past acquisitions, the U.S. group has come under fire in Britain, the United States and Sweden as it weighs its next move to buy AstraZeneca, which could be a sweetened offer next week.