Late yesterday, District Judge Sue Robinson in Delaware announced a ban on Regeneron Pharmaceuticals Inc. (NASDAQ:REGN) and French firm Sanofi SA from selling their cholesterol drug, Praluent in the US on the grounds of patent infringement.
Amgen had sought a ban in an October 2014 lawsuit against the two firms claiming that Praluent, which lowers so-called "bad" cholesterol by blocking a protein known as PCSK9, infringed its patents related to that protein.
Blocking sales of Praluent, the judge said that "irreparable harm" had been done to Amgen's own cholesterol-lowering treatment, Repatha.
In early New York trading today, Amgen shares jumped 3% higher to $157, while shares in Regeneron dropped over 6% to $356.
However, Judge Robinson ordered that the ban not take effect for 30 days to give Sanofi and Regeneron time to appeal, which they said they would do.
In a statement today, Sanofi's executive vice president Karen Linehan said: “"It is our longstanding position that Amgen's patent claims are invalid and that the best interests of patients will be greatly disserved by an injunction preventing access to Praluent."
A jury found Amgen's patents were valid in March.
Commentators said the companies could still decide to reach a settlement that would give Amgen royalties on Praluent sales.
The US Food and Drug Administration approved Praluent and Repatha in 2015, and both are currently in final stage trials.