Amgen: Markush Practice in 2020

• Publication year: 2020
• Author: D. Benjamin Borson

AmGen: Markush Practice in 2020

D. Benjamin Borson

Borson Law Group P.C.

AMGEN INC. V. AMNEAL PHARMACEUTICALS LLC, PIRAMAL HEALTHCARE UK LIMITED, CADILA HEALTHCARE LTD., DBA ZYDUS CADILA (ZYDUS PHARMACEUTICALS (USA) INC.)

Slip Op 2018-2414, 2019-1086

Federal Circuit, 7 January 2020, 11 February 2020

Introduction

Amgen Inc. ("Amgen") is the owner of U.S. Patent No 9,375,405 (the '405 patent). Claims of this patent are drawn to pharmaceutical compositions comprising a therapeutically effective amount of a calcium receptor-active compound, at least one excipient, and a binder. Amgen holds approved New Drug Application No. 21688 for Sensipar^®, a formulation of cinacalcet hydrochloride used to treat secondary hyperparathyroidism in adult patients with chronic kidney disease who are on dialysis to treat hypercalcemia in patients with parathyroid cancer and primary and secondary hyperparathyroidism.

Amneal Pharmaceuticals LLC ("Amneal"), Piramal Healthcare UK Limited ("Piramal"), and Cadila Healthcare Ltd., DBA Zydus Cadila (Zydus Pharmaceuticals (USA) Inc.) ("Zydus") ("defendants"), each filed Abbreviated New Drug Applications (ANDAs) seeking to enter the market with a generic version of Sensipar.^®

Amgen sued the defendants for patent infringement of Claim 1 of the '405 patent in the District Court of Delaware based on the filing of the ANDAs.

The District Court held that Amneal does not infringe claims 1, 2-4, 6, 8-12 and 14-18, that Piramal does not infringe claims 1-6 and 8-20. However, the District Court held that Zydus and Cadila infringe claims 1-4, 6, 8-9, 15-17, and 19. Amgen appealed the decisions regarding non-infringement.

For purposes of this Appeal, the parties stipulated that infringement findings for claim 1 would extend to the majority of the remaining claims. In its decision, Judge Lourie (for Judges Lourie, Newman, and Taranto) held that "the district court construed the claims incorrectly and erred in its analysis of infringement by Amneal. However, the court properly applied prosecution history estoppel to Amgen's arguments regarding Piramal and otherwise did not err in its fact findings for Zydus. Accordingly, the court vacated and remanded the district court's judgement as to Amneal and affirmed with respect to Piramal and Zydus." Slip. Op. at 3.

This article addresses the issue of the use of open ended transitional term "comprising" in conjunction with Markush groups; namely, whether a claim that uses "comprising" in the preamble and Markush groups in the body of the claim mean that the Markush groups are open, not being limited to the recited elements, or closed to un-recited elements. Other issues of infringement are beyond the scope of this article.

Prosecution History

Judge Lourie noted that the prosecution history of the '405 patent is particularly relevant. During prosecution, because the binder and disintegrant limitations were amended into the current Markush group format prior to issue.

Claim 1 is reproduced below:

1. A pharmaceutical composition comprising:

1. from about 10% to about 40% by weight of cinacalcet HCl in an amount from about 20 mg to about 100 mg;
2. from about 45% to about 85% by weight of a diluent selected from the...