Pfizer’s (PFE.N) announcement of what is expected to be the biggest-ever healthcare deal pushed its shares down 2.6 percent making it one of the biggest drags on the S&P. Target company Allergan (AGN.N) closed 3.4-percent lower after the $160 billion deal announcement. “Today was a dull day unless you’re involved in Pfizer or Allergan. Away from that, it’s kind of aimless,” said Brian Fenske, head of sales trading at ITG in New York.