One of Pfizer Inc.’s last decisions of 2021 was to shell out $6.7 billion for San Diego’s Arena Pharmaceuticals Inc., a deal centered around the pipeline inflammatory disease pill etrasimod. A potential successor to Xeljanz (tofacitinib), the price New York-based Pfizer paid suggests blockbuster potential for etrasimod. Phase III results announced March 23 suggest Pfizer’s big acquisition, the fifth largest in biopharma in 2021, was money well spent.