Regeneron cannot immediately block U.S. sales of rival Amgen's proposed copy of its blockbuster eye-care drug Eylea, a federal judge in West Virginia said on Monday.

Three months after a federal judge in West Virginia sided with Regeneron, blocking the market entry of two biosimilars for blockbuster eye disease drug Eylea, the same judge has rejected the company’s attempt to block Amgen’s Eylea biosimilar.

Shares of Regeneron fell 5% yesterday after the company’s effort to block Amgen from launching a biosimilar version of its blockbuster eye drug Eylea hit a legal roadblock.

Adds Wells Fargo analyst comment. Regeneron Pharmaceuticals (NASDAQ:REGN) quickly dropped 3.5% after a judge denied the company's motion for a preliminary injunction to block an Amgen (AMGN) biosimilar version of Regeneron's blockbuster Eylea drug.

A federal judge rejected Regeneron's request for a preliminary injunction against Amgen in its lawsuit for Eylea's biosimilar.