Amgen

(AMGN) - Get Report

said Tuesday that it has closed the books on its $10 billion merger with

Immunex,

(IMNX)

announced late last year.

Next up for the world's largest biotech firm: A key regulatory ruling on its anemia-fighting drug, Aranesp, expected by Friday. Then, the announcement of second-quarter results on July 24 -- important because the company is expected to provide updated financial guidance.

With the merger complete, Amgen now controls the rheumatoid arthritis drug Enbrel, which, while quickly achieving blockbuster status, has also struggled through well-publicized supply constraints due to a lack of manufacturing capacity.

Amgen already has two blockbuster drug franchises in its own medicine cabinet -- the anemia-fighting combo Epogen and Aranesp, as well as Neupogen and its newer version Neulasta, used by cancer patients to boost white blood cell counts and fight off infections.

When Amgen first announced plans to buy Immunex in December, the stock-and-cash deal was valued at $16 billion. A wretched stock market for biotech firms since then has depressed both stocks, reducing the deal's price tag to around $10 billion. Each Immunex share is being exchanged for 0.44 Amgen share and $4.50 in cash.

On Friday the U.S. Food and Drug Administration is expected to issue its ruling on the approved use of Aranesp in cancer patients. If the drug gets the nod, Amgen will be able to compete directly in the lucrative cancer market against rival

Johnson & Johnson

(JNJ) - Get Report

and its drug Procrit (sold as Eprex outside the U.S.).

Amgen has already started to take on Johnson & Johnson, telling doctors this week that Aranesp is safer than Procrit/Eprex, which has been linked to 78 cases of pure red blood cell aplasia, a serious medical condition. Amgen's Aranesp and its older cousin drug, Epogen, have been linked to only four cases of the condition, according to Amgen.

At last May's annual meeting of the American Society of Clinical Oncology, Amgen presented data that showed doctors could administer Aranesp effectively to patients once every three weeks. That's more convenient, because chemotherapy regimens are typically administered on the same schedule. By comparison, Procrit/Eprex is typically dosed once a week, although Johnson & Johnson also presented data suggesting that its drug could also be given less frequently.

Amgen and Johnson & Johnson are expected to engage in one of the fiercest drug marketing battles in recent memory over their respective anemia-fighting products. Johnson & Johnson has already started to go directly to consumers with its message, broadcasting TV commercials for Procrit. If Amgen follows suit, it would become the first biotech firm to launch such an advertising campaign.

When Amgen reports consolidated second-quarter results on July 24, Wall Street analysts are expecting the company to report earnings of 35 cents a share, according to Thomson Financial/First Call. More importantly, analysts and fund managers will be listening to see if the company changes any of its financial forecasts.

Most at risk is Enbrel, which Amgen has said will post sales of just over $1 billion this year and $1.6 billion in 2003. These estimates could be in jeopardy because the drug continues to be plagued by supply constraints, biotech observers say. Enbrel sales totaled $762 million in 2001. New manufacturing capacity for Enbrel is expected to be operational by the end of the year, or early in 2003.

In March, Immunex warned doctors that Enbrel was going to be in even shorter supply than normal during April and May, forcing patients to wait for several weeks to get prescriptions filled. Some analysts believe this problem extended into June, putting second-quarter sales estimates in jeopardy.

Lazard Freres biotech analyst Joel Sendek was expecting second-quarter Enbrel sales of $194 million, but lower-than-expected sales tracking data for April and May suggest that Enbrel sales may only reach a range of $140 million to $164 million in the quarter, he says. Sendek rates Amgen a hold, and his firm doesn't have a past banking relationship with the company.

Enbrel sales in the first quarter totaled $216 million, flat with the fourth quarter of 2001. At that time, Immunex executives said second-quarter sales would be "flat to down" from the first quarter, according to an Immunex (now Amgen) spokeswoman.

If Enbrel sales do come in light for the second quarter, Amgen might still match or exceed Wall Street estimates, because sales of Neulasta are tracking stronger than expectations, according to some analysts. Also, Amgen is expected to start benefiting from merger-related cost-cutting.

Wall Street analysts are expecting Amgen to earn $1.40 a share in 2002, compared with $1.18 a share in 2001. The company is expected to earn $1.70 per share in 2003.

In recent trading, Amgen was up $2.93, or 9.4%, to $34.