AstraZeneca said on Friday it has sued the US government to block parts of a program that gives the Medicare health insurance plan the power to negotiate lower drug prices. The British drugmaker, which filed its complaint in a Delaware district court, joins other drugmakers and business groups claiming that the program would restrict the development of new medicines. The program faces at least seven other court challenges, including from leading industry group PhRMA and drugmakers Johnson & Johnson, Merck & Co, Bristol Myers Squibb and privately-held Boehringer...