* Fed Chair Yellen to speak at Jackson Hole on Friday
* Medivation jumps on $14 bln Pfizer deal
* Indexes: Dow off 0.12 pct, S&P off 0.06 pct, Nasdaq up 0.12 pct (Updates to market close)
By Chuck Mikolajczak
Aug 22 (Reuters) - U.S. stocks were little changed on Monday as a drop in oil prices that weighed on the energy sector was offset with a strong showing by biotech stocks.
Oil prices settled down more than 3 percent, after touching two-month highs last week, on worries about burgeoning Chinese fuel exports, more Iraqi and Nigerian crude shipments and a rising U.S. oil rig count.
The S&P energy index lost 0.9 percent, its worst performance in two weeks, and was the worst-performing of the 10 major S&P groups.
As earnings season draws to a close, investor focus will shift to Federal Reserve Chair Janet Yellen's speech on Friday at the annual central bankers' meeting in Jackson Hole, Wyoming, to assess the odds of an interest rate hike in coming months.
"It's oil and then we've got Jackson Hole hanging over us, and there is always some surprise that comes out of Jackson Hole," said Jack Ablin, chief investment officer at BMO Private Bank in Chicago.
The case for a rate hike was bolstered by Fed Vice Chairman Stanley Fischer's comments that the U.S. economy was close to hitting the Fed's job and inflation targets.
Traders have priced in an 18 percent chance of a rate hike for September, up from 12 percent on Friday. That measure rose to about 50 percent for December, from 46.2 percent, according to the CME Group's FedWatch tool.
Biotech stocks received a boost from Pfizer's $14 billion acquisition of cancer drug maker Medivation. Medivation's shares jumped nearly 20 percent as the biggest boost to the Nasdaq, and the Nasdaq biotech index was up 2 percent, its best day since July 27.
Of the 479 companies in the S&P 500 that have reported earnings, 71 percent have topped Wall Street's expectations, according to Thomson Reuters data through Monday morning. Earnings are currently showing a decline of 2.3 percent for the quarter.
The Dow Jones industrial average fell 23.15 points, or 0.12 percent, to 18,529.42, the S&P 500 lost 1.23 points, or 0.06 percent, to 2,182.64 and the Nasdaq Composite added 6.23 points, or 0.12 percent, to 5,244.60.
Apple was off 0.8 percent as the biggest drag on all three major indexes.
Chipmaker Intersil jumped 19.8 percent $18.74 after a source told Reuters that Japan's Renesas was in the final stages of negotiations to acquire the company for about $2.99 billion.
Advancing issues outnumbered declining ones on the NYSE by a 1.01-to-1 ratio; on Nasdaq, a 1.19-to-1 ratio favored advancers.
The S&P 500 posted 14 new 52-week highs and no new lows; the Nasdaq Composite recorded 102 new highs and 20 new lows.
About 5.3 billion shares changed hands in U.S. exchanges, compared with the 6.38 billion daily average over the last 20 sessions. (Reporting by Chuck Mikolajczak; Editing by Dan Grebler and Nick Zieminski)