The chief executive officer of pharmaceutical giant Amgen Inc., Kevin Sharer, says 2007 was the "most difficult" year in the company's history.

In an interview with The Wall Street Journal, Sharer was asked about the struggles that have bludgeoned the company's stock, leaving it at a 52-week low on Friday of $44.18, down from a high of $65.10 last May.

"The last year was the most difficult in our history. We had an unexpected $800 million to $1 billion hit to operating income due to safety concerns about one of our medicines," Sharer told the newspaper. "The affected medicine, Aranesp in oncology, is half the level that it was in the U.S. a year ago. But it's stable. I regret deeply the shareholder-value consequences. But this is the most challenging time in my 16 years."

Last March, the U.S. Food and Drug Administration issued a warning related to two of Amgen's anemia drugs, Aranesp and Epogen, citing studies that reported that patients taking them in higher- than-recommended dosages had an elevated risk of "life-threatening side effects and/or death."

The two drugs generated nearly half of Amgen's sales of $14.3 billion in 2006.

Last year, to cut costs, Amgen laid off 300 of its employees in West Greenwich, where it makes the drug Enbrel, The Providence Journal reported.