Pfizer said in a statement on Sunday that it will reduce its Massachusetts workforce by about 200 employees — almost 10 percent of its headcount in the state — as it ends development of drugs aimed at Alzheimer’s and Parkinson’s disease as well as other neuroscience research programs. The New York City-based pharmaceutical company (NYSE: PFE) said the total job cuts from the restructuring will be 300, about a third each in Cambridge, Andover and Groton, Connecticut.