US STOCKS-Wall St flat as momentum stocks stabilize; Pfizer drags
* Pfizer weighs on Dow, S&P 500
* Mallinckrodt to buy Questcor for $5.6 bln
* MannKind stumbles; FDA extends drug review date
* Dow down 0.17 pct, S&P down 0.08 pct, Nasdaq up 0.09 pct (Updates to open, adds quote)
By Chuck Mikolajczak
NEW YORK, April 7 (Reuters) - U.S. stocks were little changed on Monday, as recent weakness in so-called momentum names appeared to abate while a decline in shares of Pfizer weighed on the market.
Declines in momentum shares - fast-growing companies which have outperformed the market recently - have left investors anxious about how much further they may fall.
That weakness continued early on Monday, with names such as TripAdvisor Inc down 1.6 percent to $84.30. However, other names such as Facebook Inc, up 1 percent to $57.33 and Gilead Sciences Inc, up 0.8 percent at $72.76, were able to reverse initial declines.
"There is a difference between that sense you get when it is picking up speed and becoming a one-way juggernaut either way, to the downside or the upside, and we are not seeing that," said Gordon Charlop, a managing director at Rosenblatt Securities in New York. Continuación...