US STOCKS-Futures climb after three-day run
* Futures up: Dow 45 pts, S&P 4.25 pts, Nasdaq 8.5 pts
* Gilead falls as Express Scripts chooses AbbVie treatment
* Biocryst gets FDA OK for intravenous flu drug
By Chuck Mikolajczak
NEW YORK, Dec 22 (Reuters) - U.S. stock index futures advanced on Monday, after the S&P 500 notched its best weekly performance in almost two months, as oil prices continued to show signs of stabilizing.
* Brent crude hit a high of $62.97 and WTI crude rose to as much as $58.53 amid investor confidence there would be no substantial price loss in the run-up to the new year. However, Brent pulled back to last trade down 14 cents to $61.24 while U.S. crude was last off 0.4 percent at $56.91.
* The benchmark S&P index rose 3.4 percent last week, boosted by a 5 percent jump over three sessions, after the U.S. Federal Reserve said it would take a "patient" approach toward raising interest rates and as oil prices appeared to stabilize. The S&P energy index surged nearly 10 percent for the week.
* Investors await existing home sales data, due out at 10:00 a.m. (1500 GMT). Expectations are for a decline of 1 percent.
* Trading volume is expected to be light this week due to the Christmas holiday, which could increase volatility. U.S. equity markets will operate a shortened session on Wednesday and be closed on Thursday. Continuación...