Anemic Amgen Loses Status as No. 2 Biotech

If the preliminary injunction remains in place, Farmer expects Amgen shares to rebound to the mid-$40's. "However, if Judge Young lifts the injunction, we expect AMGN stock to be hit exceptionally hard as the Street begins to see realistic threats to another major franchise which most had thought stable through 2012."

Beyond the battle with Roche, investors also are eyeing Amgen's Denosumab for post-menopausal osteoperosis. According to JPMorgan's Meacham, positive late-stage data on the drug would make risks to its other franchises look more manageable.

But, Meacham says Denosumab is already factored into Amgen's shares, and it would require very robust data to drive the stock higher. When Densumab is factored out, Meacham said he arrives at a mid-$30s value, and so he believes Amgen's 9.5 multiple to be about right.

Amgen shares were down 22 cents, or 0.5%, at 39.74 on Thursday.