Amgen's ( AMGN) shares gained 3.5% after an analyst raised his price target on the stock, saying a competitive threat appears to be waning.

Bear Stearns analyst Mark Schoenebaum said papers filed Friday put Amgen's patent suit against Roche's competing drug Cera in a better light. He said the documents suggest Cera is similar enough to Amgen's Epo to prevent Roche from launching Cera in the U.S.

Amgen should reach a year-end price target of $83, says Schoenebaum. He previously set a price target of $77. The analyst upgraded the stock to outperform from peer perform two weeks ago.

"We increased the probability Cera does not launch in the U.S. from 25% to 60%," the analyst wrote in a research report Monday. "Additional upside to our estimates could come with more definitive evidence Cera will not launch in the U.S."

Shares were up $2.58 to $76.83 Monday morning.

Bear Stearns has received noninvestment banking compensation from Amgen, and the analyst or one of his family members has a long position on the stock, the firm says.