Shares of Pfizer have been on the decline, losing some 5% from its January 5 high of $33.61 a share.
U.S. stocks were mixed Wednesday even amid better-than-expected earnings from the banking sector.
Citigroup reported fourth-quarter earnings that topped estimates. The company returned $4.7 billion of capital to shareholders during the quarter.
Goldman Sachs reported fourth-quarter earnings that topped Wall Street's estimates, thanks in part to a 25% increase in trading revenue.