AstraZeneca’s MedImmune unit has acquired AlphaCore Pharma, a privately held U.S. biotechnology company developing a new type of cholesterol medicine. Financial details were not disclosed.   AlphaCore’s lead drug candidate ACP-501, a genetically engineered liver-derived enzyme called LCAT, completed Phase I trials last year. ACP-501 is being developed to help manage cholesterol to reduce the risk of heart attacks and strokes. It could also play a role in a rare, hereditary disorder called famili...