* S&P 500 18 points shy of May 2015 record high
* Oil prices hit 2016 highs; Exxon hits 52-week high
* Biogen, Alexion drop after drug trial failures
* Indexes up: Dow 0.46 pct, S&P 0.36 pct, Nasdaq 0.1 pct (Adds details, comment, updates prices)
By Yashaswini Swamynathan
June 7 (Reuters) - The S&P 500 touched an 11-month high on Tuesday and was just 18 points shy of its record high, helped by gains in energy shares, while tumbling healthcare stocks capped gains on the Nasdaq.
The S&P energy index surged 1.79 percent as oil prices hit 2016 highs due to supply constraints and a weak dollar.
Chevron rose 2 percent, while Exxon gained as much as 1.5 percent to a 52-week high of $90.68. The stocks were among those giving the biggest boost to the S&P and the Dow.
"Demand for oil seems to be stronger than we anticipated and the price continues to rise, that is something that is positive," said Kim Forrest, senior equity research analyst, Fort Pitt Capital Group in Pittsburgh.
The healthcare index dropped 0.55 percent, dragged down by Biogen and Alexion, both of which reported that their drugs failed in trials.
Still, nine of the 10 major S&P sectors were higher a day after Federal Reserve Chair Janet Yellen expressed confidence in the health of the economy, but was vague on when the central bank would raise interest rates.
"It feels like markets want to move higher even though there is no real reason for us to pay more. Its a head scratcher," Forrest said.
At 11:15 a.m. ET (1443 GMT) the Dow Jones Industrial Average was up 82.33 points, or 0.46 percent, at 18,002.66, breaching the 18,000 mark for the first time since April 28.
The S&P 500 was up 7.59 points, or 0.36 percent, at 2,117.11, about 18 points shy of its record high of 2134.72, hit on May 2015.
The Nasdaq Composite eked out a gain of 5.07 points, or 0.1 percent, to 4,973.78, weighed down by a 2.4 percent drop in the Nasdaq biotech index.
Biogen tumbled 13 percent to $252.31 after its multiple sclerosis drug failed in a mid-stage study, and was the biggest drag on the Nasdaq and the S&P.
Alexion dropped 11 percent to $137.96 after its drug failed a late-stage trial.
Valeant's shares slumped 14 percent to $24.83 after the drugmaker cut its full-year forecast.
Advancing issues outnumbered decliners on the NYSE by 1,891 to 922. On the Nasdaq, 1,298 issues rose and 1,248 fell.
The S&P 500 index showed 32 new 52-week highs and one new low, while the Nasdaq recorded 47 new highs and 11 new lows. (Reporting by Yashaswini Swamynathan in Bengaluru; Editing by Savio D'Souza)