Immunex (IMNX) Wednesday said third-quarter earnings rose 50%, in line with analyst forecasts, fueled by rising sales of its lead drug Enbrel for rheumatoid arthritis.

Immunex said net income rose to $31.5 million, or 6 cents per share, from $21 million, or 4 cents per share, a year ago. Revenue rose to $219 million from $152.4 million a year ago.

"Immunex has hit the mark operationally," said CEO Ed Fritzky. "Consistently growing product sales and strong positive cash flow from operations have built a strong financial base for the company."

Enbrel, by far its biggest product, generated $172.1 million in third-quarter sales, up 69% from a year ago and in line with analysts' forecasts of $170 million - $178 million. The drug, which is expected to be a multibillion-dollar drug at peak sales, generated sales of $155 million in the second quarter.

Seattle-based Immunex has been about 55% held by

American Home Products

(AHP)

, which co-markets Enbrel. In August, American Home said it may cut its stake to 43% by selling as many as 50 million Immunex shares. Immunex also said it would sell 20 million newly issued shares.

Immunex said sales of other products, including cancer drugs Leukine and Novantrone, rose 24% to $44.8 million in the quarter. The

Food and Drug Administration

this month approved Novantrone, a prostate and leukemia treatment, for certain types of multiple sclerosis. But analysts say side effects may limit its use in this market.

Shares in Immunex, one of the first profitable and among the most heavily traded biotech companies, have fallen from a high of 83 in March to close Wednesday at $46.19, following a similar pattern for many biotechs.

Enbrel was approved for broader use in moderate rheumatoid arthritis patients in June, a far bigger market than the severe form of the debilitating disease that the drug was approved for in late 1998. The company estimates there are 350,000 patients with severe RA in the U.S., while 700,000 people have moderate RA.

Research and development expenses rose to $44.2 million, up from $31.1 million in the third quarter of 1999.