Pfizer says it’s going to keep its research unit in St. Louis and expand it. The unit had been owned by Pharmacia Corporation, with offices in Creve Coeur, Chesterfield, and at the Washington University School of medicine. One-thousand people work for the unit now. Pfizer is the world’s biggest pharmaceutical company. Among the widely-used drugs developed by the group in the St. Louis area – Celebrex, Bextra, Dynastat, and Somavert.