* Britain triggers Article 50 to exit EU
* Vertex jumps on success of cystic fibrosis treatment
* Dow down 0.16 pct, S&P down 0.09 pct, Nasdaq up 0.09 pct (Updates to open)
By Yashaswini Swamynathan
March 29 (Reuters) - U.S. stocks were little changed on Wednesday as investors awaited comments from a host of Federal Reserve officials for clues on the number of interest rate hikes this year.
Chicago Fed President Charles Evans, who has consistently been dovish on interest rates, said he supported one or two more hikes this year as the U.S. economy improves.
Boston President Eric Rosengren and his San Francisco counterpart, John Williams, are due to speak later in the day.
Investors also appeared to remain on the sidelines, expecting some uncertainty after Britain started a process to exit the European Union.
Nine months after Britons voted to leave, British Prime Minister Theresa May notified EU Council President Donald Tusk in a letter that the UK is quitting the bloc it joined in 1973.
The dollar rose on the Brexit development, building on gains from a day earlier, while prices of safe-haven gold also moved higher on uncertainty regarding trade policies between the EU and Britain.
Wall Street showcased an impressive recovery on Tuesday, with the Dow snapping an eight-day losing streak after robust consumer data pointed to the strength in the U.S. economy and eased jitters about the impact of a failed healthcare bill.
"The markets are tranquil after yesterday's new burst of confidence rally forced shorts to cover," Cardillo wrote.
At 9:41 a.m. EDT the Dow Jones industrial average was down 32.26 points, or 0.16 percent, at 20,669.24, the S&P 500 was down 2.21 points, or 0.09 percent, at 2,356.36 and the Nasdaq Composite was up 5.27 points, or 0.09 percent, at 5,880.41.
Six of the 11 major S&P 500 sectors were lower, with utilities taking the biggest blow.
Berkshire Hathaway was the top drag on the S&P, while Goldman Sachs pulled down the Dow.
Vertex Pharmaceuticals, jumped nearly 22 percent to $109.65 after its cystic fibrosis treatment succeeded in a late-stage trial.
Luxury furniture retailer RH was up 11.3 percent at $42.41 following a quarterly profit that beat analysts' expectations.
Chipmaker Exar Corp was up 22 percent at $12.95 following a deal to be bought by Maxlinear for about $700 million.
Declining issues outnumbered advancers on the NYSE by 1,483 to 1,121. On the Nasdaq, 1,273 issues fell and 992 advanced.
The S&P 500 index showed eight 52-week highs and one low, while the Nasdaq recorded 27 highs and 11 lows. (Reporting by Yashaswini Swamynathan in Bengaluru; Editing by Anil D'Silva)