One correct way of reciting a Markush group in the claim
| January 24, 2020
Amgen Inc. v. Amneal Pharmaceuticals LLC
January 7, 2020
Lourie (Opinion author), Newman, and Taranto
Summary
The Federal Circuit reversed the district court’s claim construction of the Markush groups as being closed to unrecited elements because the claim recites “comprising” as the transitional phrase and “at least one” in front of each of the Markush groups. Furthermore, the Federal Circuit affirmed the district court’s holding of noninfringement under the doctrine of equivalents by one of the Defendants’ products due to prosecution history estoppel.
Details
Amneal, Piramal, and Zydus each filed an Abbreviated New Drug Application (ANDA), seeking approval of a generic version of Sensipar®, a formulation of cinacalcet hydrochloride used to treat secondary hyperparathyroidism in adult patients with chronic kidney disease who are on dialysis and to treat hypercalcemia in patients with parathyroid cancer and primary and secondary hyperparathyroidism. Amgen holds the approved New Drug Application for Sensipar®, and sued them for infringing U.S. Patent No. 9,375,405 (the ‘405 patent).
The ‘405 patent is directed to a rapid dissolution formulation of cinacalcet. Claim 1 of the ‘405 patent is as follows:
A pharmaceutical composition comprising:
(a) from about 10% to about 40% by weight of cinacalcet HCl in an amount of from about 20 mg to about 100 mg;
(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,
wherein the percentage by weight is relative to the total weight of the composition, and wherein the composition is for the treatment of at least one of hyperparathyroidism, hyperphosphonia, hypercalcemia, and elevated calcium phosphorus product.
The ‘405 patent issued from U.S. Patent Application 12/942,646 (the ‘646 application). The original ‘646 application contained only one claim, which recited a “pharmaceutical composition comprising an effective dosage amount of a calcium receptor-active compound and at least one pharmaceutically acceptable excipient, wherein” the composition achieved a specific dissolution profile. Later, Amgen filed a Preliminary Amendment, which cancelled claim 1 and added new claims 2-24. The newly filed claim 2, which ultimately issued as claim 1, is as follows:
A pharmaceutical composition comprising:
(a) from about 10% to about 40% by weight of cinacalcet HCl;
(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; and
(d) from about 1% to 10% by weight of at least one disintegrant,
wherein the percentage by weight is relative to the total weight of the composition.
The Examiner rejected the new claims. Then, Amgen filed an amendment of the independent claim 2, reciting “from about 10% to about 40% by weight of cinacalcet HCl in an amount of from about 20 mg to about 100mg.” Then, Amgen conducted a phone interview with the Examiner. During the interview, the Examiner proposed an Examiner’s Amendment of the independent claim 2, and Amgen accepted the Examiner’s Amendment. Specifically, the Examiner’s Amendment revised the binder and the disintegrant limitations into their current, Markush group format. Then, the claims are allowed. After the Notice of Allowance was issued, Amgen filed a number of RCE Requests with new IDS submission. In one of the RCE Requests, with regard to the previous Examiner’s Amendments, Amgen remarked that “[t]hese amendments have not been made in response to a prior art rejection but rather to place the claims in proper format and to better define the claimed subject matter, including equivalents.” The Examiner issued a Notice of Allowance after each RCE Request.
In the district court proceeding, one key issue is the construction of the binder and disintegrant Markush groups. The district court held that the Markush groups for the binder and disintegrant elements are closed to unrecited binders and disintegrants, relying on Multilayer Stretch Cling Film Holdings, Inc. v. Berry Plastics Corp., 831 F.3d 1350 (Fed. Cir. 2016). Furthermore, the district court held that Amneal does not infringe the ‘405 patent because Amneal uses Opadry Clear YS-1-7006 as the binder, a product that contains PEG 400 and PEG 8000 in addition to hydroxypropyl methylcellulose, which is a listed binder in claim 2. Furthermore, the district court held that Piramal does not infringe the ‘405 patent under the doctrine of equivalents because prosecution history estoppel barred Amgen’s argument that the cold-water soluble fraction of the preglatinized starch used by Piramal is equivalent to providone, a listed binder in claim 2.
On appeal, first, the Federal Circuit reversed the district court’s claim construction regarding the binder and disintegrant Markush groups. Specifically, contrary to the district court’s interpretation, because claim 1 uses “comprising” as the transitional phrase and “at least one” in front of each Markush group, the binder and disintegrant Markush groups do not preclude other binders and disintegrants in the claimed composition. Without more, such language is satisfied when an accused product contains a component that is from the Markush group and that meets the limitation’s other requirements such as concentration requirement for the component. Furthermore, the Federal Circuit held that Opadry used as a binder by Amneal contains HPMC, which is a listed binder in claim 1. Thus, irrespective of whether other components such as PEG are present, provided that Amneal’s formulation contains from about 1 to about 5% HPMC, the formulation literally infringes. Accordingly, the Federal Circuit vacates and remands those findings by the district court.
Next, the Federal Circuit held that Amgen’s doctrine of equivalents argument is barred by prosecution history estoppel. During the prosecution, Amgen accepted the Examiner’s Amendment that revised the claim’s disintegrant and binder limitations to be in Markush group format. Such an amendment narrows the scope of the claim, and Amgen failed to carry its burden to demonstrate that the Examiner’s Amendment was made for a reason unrelated to patentability. The Amgen’s statement in the later RCE Request was made over eight months after the Examiner’s Amendment was accepted, and accordingly does not provide any insight on the reasons for the Examiner’s Amendment. Furthermore, the tangential exception to prosecution history estoppel does not apply here because the use of pregelatinized starch as a binder is taught in the cited prior art. An amendment made to avoid prior art that contains the equivalent in question is not tangential.
Accordingly, the Federal Circuit vacated and remanded the district court’s judgment that Amneal does not infringe the ‘405 patent, and affirmed the district court’s judgment that Piramal does not infringe the ‘405 patent.
Take away
- The claims should recite “comprising” as the transitional phrase and “at least one” in front of the Markush groups to avoid being constructed to be closed to unrecited elements in the Markush groups.
- The original specification should contain a complete set of claims instead of one claim because later amendments may inevitably invoke prosecution history estoppel, which would bar most of the doctrine of equivalents arguments.
- The patent drafter should be mindful of an independent claim with an overly broad scope. Any later amendments during the patent prosecution may invoke prosecution history estoppel. Accordingly, the applicants have the risk of losing any protection afforded by patent infringement under the doctrine of equivalents.
