US STOCKS-Wall St ends down as biotechs drop 4 pct
* Apple shares up ahead of results
* Amgen's fall drags downs biotech stocks
* Celladon nosedives on lead drug's trial failure
* Indexes down: Dow 0.23 pct, S&P 0.41 pct, Nasdaq 0.63 pct (Updates to close)
By Caroline Valetkevitch
April 27 (Reuters) - U.S. stocks ended down on Monday, led by losses in biotech shares after disappointing news from several companies including Amgen.
The Nasdaq Biotech Index sank 4.1 percent, its biggest daily percentage loss since March 25, while the S&P Healthcare index, down 1.8 percent, was the biggest drag on the benchmark S&P 500 index.
Amgen shares led the S&P 500's decline, dropping 3.3 percent to $162.38 after U.S. regulators said Amgen's skin cancer immunotherapy cannot be considered for an accelerated review at this time.
Celladon Corp shares fell 80.7 percent to $2.64 and hit a record low of $2.59. It said it expected layoffs and cost cuts after the company's lead experimental gene therapy to treat heart failure failed a key trial. Continuación...