Amgen Inc. v. Amneal Pharms. LLC

Case Name: Amgen Inc. v. Amneal Pharms. LLC, 2018-2414, 2019-1086, 2020 U.S. App. LEXIS (Fed. Cir. Jan. 7, 2020) (Circuit Judges Newman, Lourie, and Taranto presiding; Opinion by Lourie, J.) (Appeal from D. Del., Goldberg, J.)

Drug Product and Patent(s)-in-Suit: Sensipar® (cinacalcet); U.S. Patent No. 9,375,405 (“the ’405 patent”)

Nature of the Case and Issue(s) Presented: Amgen’s drug product Sensipar® is a formulation of cinacalcet hydrochloride used to treat hyperparathyroidism and hypercalcemia. Amgen sued Amneal, Piramal, and Zydus after each filed ANDAs for generic versions of Sensipar. After a bench trial, the district court found that Amneal and Piramal did not infringe any claim of the ’405 patent but that Zydus did infringe the asserted claims. Amgen appealed, and Zydus cross appealed. The Federal Circuit vacated and remanded the district court’s finding of no infringement as to Amneal, affirmed the finding of no infringement as to Piramal, and affirmed the infringement finding as to Zydus.

Why Piramal Prevailed: The Federal Circuit affirmed the judgment of non-infringement in favor of Piramal. Piramal’s product contains a pregelatinized starch as a binder. Amgen argued that the doctrine of equivalents applied and that the cold-water soluble fraction of the starch is equivalent to povidone, listed in the representative claim’s binder Markush group. The district court found that Amgen was barred from asserting this argument by prosecution history estoppel because Amgen narrowed its claims by accepting the Examiner’s Amendment to revise its binder and disintegrant limitations into Markush group form. In doing so, the district court found that Amgen accepted the exclusion of binders different from those listed in the Markush groups. The Federal Circuit found that the district court properly applied prosecution history estoppel to bar Amgen’s claims against Piramal. Despite Amgen’s arguments to the contrary, the Federal Circuit held that Amgen had not overcome the presumption of estoppel, because the Markush limitations were added for reasons of patentability. Amgen had surrendered equivalent but unclaimed binders and disintegrants, the Federal Circuit found, so Piramal’s product did not infringe the ’405 patent.

Next, the Federal Circuit reversed and remanded the district court’s judgment of non-infringement in favor of Amneal. Claim 1 of the ’405 patent recites a pharmaceutical composition comprising cinacalcet plus a diluent, at least one binder, and at least one disintegrant each addressed by a separate Markush group. In a proposed pretrial order before the district court, Amgen argued that its Markush groups should be open to unrecited constituents. But the district court, relying on Multilayer Stretch Cling Film Holdings, Inc. v. Berry Plastics Corp., 831 F.3d 1350 (Fed. Cir. 2016) and Shire Dev., LLC v. Watson Pharms., Inc., 848 F.3d 981, 984 (Fed. Cir. 2017), followed the “very strong presumption” that Markush groups are closed to unrecited elements, and Amgen had not overcome that presumption. On appeal, Amgen challenged the district court’s construction of the binder and disintegrant Markush groups. Amgen argued that the “comprising” terminology in Claim 1 opened the claim to unlisted constituents, and the “consisting of” language is only applicable to the group from which “at least one” binder or disintegrant must be selected. The Federal Circuit agreed, finding that the district court’s reliance on Multilayer was too broad, and that the case did not stand for the limitation that all claims containing “consisting of” Markush group language are closed. The Federal Circuit held that the binders or disintegrants in the formulation in Claim 1 are not limited to the binders listed within the Markush groups. Thus, the district court’s finding that Amneal’s proposed products contained a recited disintegrant and an unrecited disintegrant, and therefore did not infringe the binder limitation of representative Claim 1, was reversed. The Federal Circuit also reversed the district court’s finding that Amneal did not infringe because it contained the binder Opadry Clear YS-1-7006 (“Opadry”), not the recited hydroxypropyl methylcellulose (“HPMC”). The Federal Circuit held that the presence of two additional polyethylene glycol components in Opadry along with HPMC did not mandate a judgment of non-infringement and remanded for further proceedings in light of the change in the construction.

Finally, the Federal Circuit affirmed the judgment of infringement as against Zydus. Zydus’s ANDA product contains a pregelatinized starch that Zydus argued functions as a binder, while Amgen argued functions as a diluent. Claim 1 of the ’405 patent lists starch in the diluent Markush group. On appeal, Zydus argued that Amgen failed to prove that pregelatinized starch is a listed binder in Zydus’s product. Zydus also argued that it was improper for the district court to consider testimony from other defendants’ experts in evaluating Zydus’s products. The Federal Circuit found that the district court did not err in its fact finding for Zydus. According to the Federal Circuit, the district court identified problems in Amgen’s expert’s opinion on starch fractions but properly applied his opinion that the pregelatinized starch in Zydus’s product functions only as a diluent. Further, the Federal Circuit found that the district court did not improperly compare the accused products.