While you were sleeping: UPDATED Brexit under way, Wall Street mixed

Wall Street was mixed, following Tuesday's rally, while the British pound weakened as the UK formally began its exit from the European Union.

Meanwhile, US Federal Reserve Bank of Boston President Eric Rosengren said the "base-case" is for four interest rate increases this year.

The central bank hiked its target rate by a quarter percentage point at its most recent meeting earlier this month and flagged a total of three increases in 2017.

"My own view is that an increase at every other [Federal Open Market Committee] meeting over the course of this year could and should be the committee's default, unless economic data come in inconsistent with forecasts," Mr Rosengren said in prepared remarks for a speech in Boston.

"The base case would be four tightenings, reflecting the strength of the economy that I believe justifies more regular normalisation of interest rates."

Dow drops, S&P rises
Wall Street was mixed. At the close of trading in New York, the Dow Jones Industrial Average fell 42.18 points, or 0.2%, to 20,659.32. However, the Nasdaq Composite Index rose for the fourth consecutive session, adding 0.4% to 5897.55 while the Standard & Poor's 500 Index rose 0.1% to 2361.13.

"We're going to be fairly range-bound as we get to the earnings season or until there is some significant development on tax reforms," Michael Scanlon, portfolio manager at Manulife Asset Management in Boston, told Reuters.

The Dow moved lower as slides in shares of UnitedHealth Group and those of Travelers, down 1.2% and 0.8% respectively, outweighed gains in shares of Merck and those of Pfizer, up 1.0% and 0.7% respectively.

The latest US housing data offered further signs of strength. A National Association of Realtors report showed its pending home sales index climbed 5.5% to 112.3 in February, the highest in 10 months and up from 106.4 in January.

"Buyers came back in force last month as a modest, seasonal uptick in listings were enough to fuel an increase in contract signings throughout the country," Lawrence Yun, NAR chief economist, said in the report.

"The stock market's continued rise and steady hiring in most markets is spurring significant interest in buying, as well as the expectation from some households that delaying their home search may mean paying higher interest rates later this year."

Drug companies advance
Vertex Pharmaceuticals shares soared 20% after the company said its cystic fibrosis treatment succeeded in a clinical trial.

"The tezacaftor/ivacaftor combination treatment demonstrated clinically meaningful benefits, with a favourable safety profile, across multiple patient groups," Vertex executive vice president Jeffrey Chodakewitz said in a statement.

"This combination treatment may provide a promising new option for treating the underlying cause of CF in the future and brings us increasingly closer to our goal of developing new medicines for all people with the disease."

Regeneron Pharmaceuticals rose 3.0% and Sanofi gained 0.7% in Paris after the US Food and Drug Administration announced approval for their new dermatitis drug.

In Europe, the Stoxx 600 Index finished the day with a 0.3% increase from the previous close. The UK's FTSE 100 Index advanced 0.4%, as did Germany's DAX Index, while France's CAC40 Index gained 0.5%.

The UK pound weakened 0.4% against the US dollar, while the euro slid 0.6%, as UK Prime Minister Theresa May triggered Article 50, formally beginning the country's exit from the European Union.

"We're in for a long period of volatility for the pound and UK assets," Neil Wilson, a market analyst at ETX Capital, wrote in a note, Bloomberg reported. "Details are everything now."

(BusinessDesk)