(Bloomberg) -- Activist investor Starboard Value has taken a stake of about $1 billion in Pfizer Inc. and is seeking to spur a turnaround of the struggling pharmaceuticals giant, according to a person familiar with the matter.Most Read from BloombergSingapore Ends 181 Years of Horse Racing to Make Way for HomesFrom Cleveland to Chicago, NFL Teams Dream of Domed StadiumsWhat Do US Vehicle Regulators Have Against Tiny Cars?For a Master of Brutalist Provocations, a Modest Museum AppraisalMexico Cit