Biotech is holding its own, and one fund manager is sticking with an investment in Amgen (AMGN) during these rough times in the markets.

The Dow Jones Industrial Average is down about 40% in the past year. The broader S&P 500 index has fallen slightly further in percentage terms.

Meanwhile, the AMEX Biotech Index is down about 26%. That's certainly not great. But in this market, that means some investors haven’t entirely lost faith in the sector, as they seem to have in many others.

Helping to keep things afloat is Amgen, the world’s largest biotech company and a pioneer in the use of living cells to create remedies for human illnesses.

“They’ve got some very positive things happening. It’s a holding we like,” said Bob Schaeffer, portfolio manager of the $50 million Becker Value Equity Fund.

For instance, Schaeffer cited new positive data related to Amgen’s anti-inflammatory medicine Enbrel, which is used by people suffering from moderate to severe rheumatoid arthritis.

The new data, which was presented recently at the American College of Rheumatology Scientific Meeting in San Francisco, indicates that Enbrel is safe and effective for long-term use.

“They’ve had some very good results with this. It could be a very effective drug,” said Schaeffer.

More important, perhaps, was Amgen’s third-quarter earnings report last week.

The numbers certainly justified the faith shown by fund managers such as Schaeffer. Profits rose five-fold to $1.16 billion, or $1.09 a share, from $201 million, or 18 cents, as sales of many of its major drugs soared. Revenue jumped 7% to $3.9 billion.

The increase in sales numbers prompted the Thousand Oaks, Calif.-based company to raise its earnings projections for all of 2008.

Particularly strong were sales of Amgen’s anemia drugs Aranesp and Epogen.

During a conference call with investors last week, Amgen Chief Executive Officer Kevin Sharer said he is optimistic that recent troubles are behind the company, which last summer announced a restructuring that included 2,600 job cuts and cancelling plans for a $1 billion manufacturing plant in Ireland.

“I have never been more energized or enthused by our prospects. We have been tested by the past 18 months and are stronger for it,” said Sharer.

Before the financial crisis arrived to pummel all stocks, Amgen saw its shares fall 32% in 2007 after revenue from some of its more prominent drugs began to contract. But the stock is up 17% in 2008, marking a sharp divergence with most of the rest of the stock market.

“We think it’s a very, very attractive valuation,” said Schaeffer.