By Bill Berkrot

Worldwide sales of Aranesp, which boosts red blood cell production in anemic chemotherapy patients, fell a larger than expected 15 percent to $706 million.

Even with diminished expectations due to safety concerns and reimbursement restrictions, analysts were looking for $754 million in Aranesp sales after a surprisingly strong third quarter. The company also issued a 2009 revenue forecast below Wall Street expectations and Amgen shares fell 2.6 percent.

All eyes are now on denosumab, an experimental osteoporosis and bone cancer treatment widely expected to become Amgen's most crucial future growth driver. Eagerly anticipated clinical data on the drug is expected to be unveiled in later this year.

"The important thing is the upcoming data on denosumab," said Cowen & Co analyst Eric Schmidt. "Those results will far overshadow any financials."

The world's largest biotechnology company posted a net profit of $961 million, or 91 cents per share, compared with a profit of $835 million, or 76 cents per share, a year ago.

Excluding items, Amgen earned $1.06 per share, topping analysts' average expectations by a penny, according to Reuters Estimates.

"In the current environment, coming in in-line is a real victory," said Sanford Bernstein analyst Geoffrey Porges.

Still, "it's hard to find anything to get terribly excited about if you are bullish," he added.

Amgen expects 2009 earnings, excluding items, of $4.55 to $4.75 per share on revenue of $14.8 billion to $15.2 billion. Wall Street is looking for earnings of $4.68 per share and revenue of $15.43 billion.

"If the stock is off in the after market, that might be the culprit," Schmidt said of the lighter-than-expected revenue forecast, adding he would not be surprised if the stock rose on Tuesday.

Revenue for the fourth quarter was flat at $3.75 billion and roughly in line with expectations.

Sales of Epogen, an older version of Aranesp used primarily in kidney dialysis patients, edged 1 percent higher to $646 million, topping analyst expectations of $632 million.

The rheumatoid arthritis and psoriasis drug, Enbrel, saw sales rise 7 percent to $913 million, eclipsing Wall Street estimates of $894 million, while combined worldwide sales of the white blood cell boosters Neupogen and Neulasta rose 6 percent to $1.12 billion, just shy of analyst expectations of $1.19 billion.

Amgen shares fell to $53 in after hours trading from their Nasdaq close at $54.41.

(Additional reporting by Lewis Krauskopf and Deena Beasley)

(Reporting by Bill Berkrot; Editing by Andre Grenon)