Wells Fargo analyst Jim Birchenough downgraded Regeneron Pharmaceuticals to Market Perform after his calls with retinal specialists indicated growth headwinds for Eylea and concerns regarding the impact of proposed Medicare Part B changes in the retinal disease space. Feedback suggests Eylea's market share gains against Lucentis and Avastin have tempered while the drug's traction in displacing laser for diabetic macular edema has been limited, Birchenough tells investors in a research note. Further, experts the analyst spoke to believe the imminent changes to Medicare Part B reimbursement suggest that practices will lose money in prescribing Eylea. Birchenough cut his price target range for the shares to $395-$431 from $450-$539. Regeneron closed yesterday down $8.60 to $413.78.