IP Law Daily District court erred in finding that Amneal’s generic Sensipar® product did not infringe Amgen patent
Tuesday, January 7, 2020

District court erred in finding that Amneal’s generic Sensipar® product did not infringe Amgen patent

By Cheryl Beise, J.D.

On remand, the court must reconsider whether Amneal’s ANDA product is infringing under the correct claim construction.

The U.S. Court of Appeals for the Federal Circuit has reversed and remanded a district court’s judgment that Amneal Pharmaceuticals’ generic version of Amgen’s brand-name drug Sensipar® infringed several claims of an Amgen patent directed to compositions covering Sensipar®. The district court improperly construed the binder and disintegrant Markush groups of the asserted claims as closed groups. On remand, the district court was directed to reconsider whether Amneal’s ANDA product is infringing, applying the corrected claim construction. However, the district court correctly ruled that Zydus Pharmaceuticals’ ANDA product infringed the asserted claims and that Piramal Healthcare’s ANDA product was noninfringing because it did not meet the binder limitation and prosecution history estoppel barred Amgen’s arguments under the doctrine of equivalents (Amgen Inc. v. Amneal Pharmaceuticals LLC, January 7, 2020, Lourie, A.).

Amgen Inc. owns U.S. Patent 9,375,405 (the ’405 patent), titled "Rapid Dissolution Formulation of Calcium Receptor-Active Compound." The ’405 patent is listed in the Orange Book as covering the brand-name drug Sensipar®. Amgen accused several companies of infringing the ’405 patent by filing Abbreviated New Drug Applications (ANDAs) seeking FDA approval to make and sell generic versions of Sensipar®. The district court construed certain claims and proceeded to a bench trial on the issue of infringement. The court bifurcated invalidity counterclaims filed by Zydus for later consideration. Following the infringement bench trial, district court held that ANDA products proposed by Amneal Pharmaceuticals LLC and Amneal Pharmaceuticals of New York LLC (collectively, "Amneal") and Piramal Healthcare UK Ltd. ("Piramal") did not infringe any claim of the ’405 patent but that an ANDA product proposed by Zydus Pharmaceuticals (USA) Inc. and Cadila Healthcare Ltd. (collectively, "Zydus") infringed claims 1–4, 6, 8–9, 15–17, and 19.

Amgen appealed from the district court’s judgment that Amneal and Piramal did not infringe the ’405 patent. Zydus cross-appealed from the district court’s judgment that it infringed the patent. Zydus’s appeal noted that the district court had not yet addressed its invalidity contentions.

Appellate jurisdiction. The first issue the Federal Circuit considered was whether the district court’s infringement decision was an appealable final judgment. The district court expressly conditioned its infringement judgment on the ’405 patent’s claims being found "valid and enforceable." Thus, by its own terms, the district court’s judgment was not a "final decision." However, Zydus represented at oral argument that it would "give up" its invalidity defense and claim regardless of outcome of the infringement appeal. As a result, the appellate court decided that Zydus’s representation effectively cured the jurisdictional defect "because the contingency identified by the district court ... is nullified."

Claim construction. The parties stipulated that the infringement findings for claim 1 would apply to all of the claims at issue on appeal. Claim 1 recites a pharmaceutical composition combining: (a) from about 10% to about 40% by weight of the active ingredient cinacalcet hydrochloride ("cinacalcet HCI"); (b) from about 45% to about 85% by weight of a diluent selected from the group consisting of microcrystalline cellulose, starch, dicalcium phosphate, lactose, sorbitol, mannitol, sucrose, methyl dextrins, and mixtures thereof; (c) from about 1% to about 5% by weight of at least one binder selected from the group consisting of povidone, hydroxypropyl methylcellulose, hydroxypropyl cellulose, sodium carboxymethylcellulose, and mixtures thereof; and (d) from about 1% to 10% by weight of at least one disintegrant selected from the group consisting of crospovid[o]ne, sodium starch glycolate, croscarmellose sodium, and mixtures thereof.

Amgen challenged the district court’s construction of the binder and disintegrant Markush groups in elements (c) and (d), respectively, on the ground that neither group forecloses the use of unlisted binders or disintegrants. Amgen cited the "comprising" and "at least one" language in the claim to support its position. The district court held that both of these Markush groups were closed.

The Federal Circuit agreed with Amgen. The court observed that there is no language in Amgen’s claim indicating that every binder or disintegrant in the claimed formulation must be within the Markush groups. Instead, the claim recites "at least one" binder or disintegrant "selected from the group consisting of" various excipients. In addition, Amgen’s use of the "comprising" transition phrase reinforced the conclusion that the language of the limitations "is best construed not to foreclose such additional binders and disintegrants," the court said. The Federal Circuit concluded that optional additional binders and disintegrants not recited in the Markush group may be included in the claimed formulation. Nothing in the specification or in the prosecution history supported a different conclusion. The district court accordingly erred in construing the claims to exclude formulations with additional unlisted ingredients.

Amneal’s product. Because the Federal Circuit reversed the district court’s claim construction, it also reversed its finding that Amneal’s product was non-infringing due to the presence of an additional, unlisted disintegrant (pregelatinized starch). On remand, the court was directed to consider whether Amneal’s product meets the disintegrant limitation under the corrected construction.

The Federal Circuit additionally reversed the district court’s factual finding that Amneal’s ANDA product met the binder limitation. As a binder, Amneal uses Opadry Clear YS-1-7006, a product that contains hydroxypropyl methylcellulose ("HPMC"), polyethylene glycol ("PEG") 400, and PEG 8000. Although HPMC was a listed binder, the district court found that Opadry itself was not, so Amneal did not literally meet the binder limitation. However, HPMC is a listed binder, and HPMC was present in Amneal’s formulation. On remand, the Federal Circuit directed the district court to "consider whether Amneal’s formulation contains ‘from about 1% to about 5% by weight’ of HPMC, irrespective of the HPMC’s pairing with PEG."

Piramal’s product. The district court found that prosecution history estoppel barred Amgen’s argument that Piramal’s product infringing under the doctrine of equivalents. Amgen had argued that the binder in Piramal’s ANDA product—pregelatinized starch—was equivalent to povidone, a binder in Amgen’s Markush list.

During prosecution, Amgen amended its claims in two ways—first, by narrowing the amount of cinacalcet to a range of 20 mg to 100 mg and second, by accepting an Examiner’s Amendment that revised the claim’s disintegrant and binder limitations be in Markush group format. Thus, Amgen surrendered equivalent but unclaimed binders and disintegrants. By agreeing to a narrowing amendment to overcome an obviousness rejection, Amgen abandoned the other binders disclosed in the prior art—which included pregelatinized starch. The Federal Circuit affirmed the district court’s ruling that Amgen was estopped from claiming equivalence to remedy a failure of the accused product to meet the Markush limitations.

Zydus’s product. In its cross-appeal, Zydus challenged the district court’s finding that its ANDA product infringed the ’405 patent. At issue was the pregelatinized starch contained in Zydus’s product. Starch is listed in the diluent Markush group. Amgen took the position that it functioned as a diluent, as stated in Zydus’s ANDA, whereas Zydus took the position that it functioned as a binder, as Zydus’s expert later testified. The Federal Circuit found that the district court did not clearly err in finding that the pregelatinized starch in Zydus’s product functioned as a diluent. The court was permitted to credit specific expert testimony, as well as the statements in Zydus’s own ANDA, that the starch in its product functioned as a diluent.

Holding. The district court’s judgment that Amneal did not infringe claims 1, 2–4, 6, 8–12, and 14–18 of the ’405 patent was vacated and remanded for further proceedings. The district court’s judgments that Piramal did not infringe claims 1–6 and 8–20 of the ’405 patent and that Zydus infringed claims 1–4, 6, 8–9, 15–17, and 19 of the ’405 patent were affirmed.

This case is Nos. 2018-2414 and 2019-1086.

Attorneys: Bradford J. Badke (Sidley Austin LLP) for Amgen Inc. Jacob M. Holdreith (Robins Kaplan LLP) for Amneal Pharmaceuticals LLC and Amneal Pharmaceuticals of New York LLC. Aaron Barkoff (McAndrews, Held & Malloy, Ltd.) for Piramal Healthcare UK Ltd. Steven A. Maddox (Maddox Edwards, PLLC) for Zydus Pharmaceuticals [USA] Inc. and Cadila Healthcare Ltd.

Companies: Amgen Inc.; Amneal Pharmaceuticals LLC; Amneal Pharmaceuticals of New York LLC.; Piramal Healthcare UK Ltd.; Zydus Pharmaceuticals [USA] Inc.; Cadila Healthcare Ltd.

MainStory: TopStory Patent FedCirNews

Back to Top

Interested in submitting an article?

Submit your information to us today!

Learn More

IP Law Daily: Breaking legal news at your fingertips

Sign up today for your free trial to this daily reporting service created by attorneys, for attorneys. Stay up to date on intellectual property legal matters with same-day coverage of breaking news, court decisions, legislation, and regulatory activity with easy access through email or mobile app.