* Apple shares up ahead of results
* Amgen's fall drags downs biotech stocks
* Celladon nosedives on lead drug's trial failure
* Indexes down: Dow 0.04 pct, S&P 0.2 pct, Nasdaq 0.5 pct (Updates to late afternoon)
By Caroline Valetkevitch
April 27 (Reuters) - U.S. stocks edged lower in Monday afternoon trading, led by losses in the Nasdaq and biotech shares including Amgen.
The Nasdaq Biotech Index was down 3.7 percent, on track for its biggest daily percentage loss in about a month, while the S&P Healthcare index, down 1.3 percent, was the biggest drag on the benchmark S&P 500 index.
Amgen shares dropped 3.2 percent to $162.53 after U.S. Food and Drug Administration staff reviewers said Amgen's skin cancer immunotherapy cannot be considered for an accelerated review at this time, citing concerns over the design and results of a key study.
Drug developer Celladon Corp shares fell 80 percent to $2.68 and hit a record low. It said it expected to announce layoffs and cost cuts after the company's lead experimental gene therapy to treat heart failure failed a key trial.
The healthcare sector is being dragged down by reports on high pricing by specialty pharmaceutical companies as well as the disapponting news from Celladon and Amgen.
"What we're seeing is a healthy correction based on multiple negative news events in the biotech space," said Paul Yook portfolio manager of biotech exchange traded funds and at LifeSci Partners in New York.
"Drug pricing has been a real concern for investors."
The Dow Jones industrial average fell 6.8 points, or 0.04 percent, to 18,073.34, the S&P 500 lost 4.22 points, or 0.2 percent, to 2,113.47 and the Nasdaq Composite dropped 26.05 points, or 0.51 percent, to 5,066.03.
Also in the healthcare space, Mylan fell 5 percent to $72.25 after it rejected Teva Pharmaceutical's unsolicited $40 billion takeover offer, saying it "grossly undervalues" the company. Teva lost 3 percent to $62.41.
Healthcare companies have been the top performers so far in 2015, helping to push major stock indexes to record levels. Biotechs like Gilead in particular have helped the Nasdaq, which last week breached its all-time closing high for the first time in 15 years.
Options on a key healthcare exchange-traded fund are set near their most defensive posture ever. Activity in puts, which can be used to hedge against a drop in shares, has picked up noticeably in April for the Health Care Select Sector SPDR ETF.
Apple shares were up 1.1 percent at $13.59 ahead of its results, due after the close. Analysts expect Apple's quarterly revenue to rise 23 percent to $56.07 billion, according to Thomson Reuters data.
The S&P 500 earlier hit a record intraday high of 2,125.92. The Nasdaq hit a high of 5,119.83, inching closer to its all-time intraday record of 5,132.52 set in March 2000.
Declining issues outnumbered advancing ones on the NYSE by 1,732 to 1,243; on the Nasdaq, 1,896 issues fell and 832 advanced.
The S&P 500 was posting 14 new 52-week highs and 1 new low; the Nasdaq Composite was recording 100 new highs and 38 new lows. (Additional reporting by Sinead Carew and Tanya Agrawal; Editing by Savio D'Souza and Nick Zieminski)