Fed Circuit issues mixed Sensipar verdict for Amgen
In a partial victory for Amgen, the US Court of Appeals for the Federal Circuit concluded that a proposed generic version of Amgen’s drug Sensipar (cinacalcet) would infringe a patent earlier this week.
On Tuesday, January 7, the Federal Circuit held that a district court had incorrectly found that Amneal’s proposed generic didn’t infringe Amgen’s patent and remanded the decision.
However, the Federal Circuit also concluded that another generic version of Sensipar, made by Zydus, didn’t infringe the patent, US patent number 9,375,405.
The patent is directed to a rapid dissolution formulation of cinacalcet, the chemical name of blockbuster drug Sensipar, which is used to treat hyperparathyroidism (overactive functioning of the parathyroid glands) in people who are on long-term dialysis for kidney disease.
Amneal, Piramal, and Zydus had each filed an Abbreviated New Drug Application (ANDA) seeking to enter the market with a generic version of Sensipar. Amgen responding by filing patent infringement suits against all three.
In a precedential decision, a three-judge panel held that Judge Mitchell Goldberg of the US District Court for the District of Delaware had erred in his analysis of the binder and disintegrant in Amneal’s formulation
In the district court litigation, the construction of the binder and disintegrant Markush groups (where a single claim defines several alternatives) was a key issue.
Amgen, in a proposed pretrial order, argued that the Markush groups should be open to unrecited elements, but the district court disagreed and, after a bench trial, found that Amneal didn’t infringe the asserted claims because its product didn’t meet the binder and disintegrant limitations.
As a binder, Amneal uses Opadry Clear YS-1-7006, a product that contains hydroxypropyl methylcellulose (HPMC), polyethylene glycol 400, and polyethylene glycol 8000.
Although HPMC is a listed binder, the district court found that Opadry itself is not, so Amneal didn’t literally meet the binder limitation.
“Because the district court’s claim constructions in this case excluded formulations with additional unlisted ingredients—binders, disintegrants, or otherwise—those constructions are incorrect,” said Circuit Judge Alan Lourie, on behalf of the Federal Circuit.
Lourie added that the is no language in Amgen’s claim “indicating that every binder or disintegrant in the claimed formulation must be within the Markush groups”.
While the issue was remanded, the Federal Circuit also concluded that Goldberg didn’t err in his fact findings for Zydus and that he had correctly applied prosecution history estoppel to find that another company, Piramal, hadn’t infringed the patent.
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