Amgen Inc. was downgraded by a Wachovia analyst Thursday because its important anemia drugs may face sharp competition soon.

On Tuesday, Roche Holding AG said it would accept the terms of a court case that said the Dutch drug company would have to pay Thousand Oaks-based Amgen a 22.5 percent royalty fee to Amgen on all sales of its drug Mircera in the United States.

A jury ruled last year that Mircera infringes on several Amgen patents resulting in sales of the drug to be halted by an injunction.

However, analyst George Farmer said that the injunction may be lifted before the end of March, resulting in a “dramatic hit” on Amgen’s dominating share of the anemia drug market. The anemia drugs made up the biggest portion of Amgen’s sales last year.

Shares in Amgen were down 1.7 percent to $39.31 in early trading hitting a 52-week-low of $39.26 during trading.