Federal Circuit: Open Transitional Phrases and Markush Groups in Pharmaceutical Claims

January 13, 2020

In one of its first precedential opinions of the new year, the US Court of Appeals for the Federal Circuit held that a claim using “comprising” as a transition phrase followed by a limitation requiring a component that “consists of” certain items listed in a Markush group is open-ended and does not exclude additional, unnamed items absent intrinsic evidence manifesting an alternative meaning. Based on the court’s reasoning, parties should remain cognizant during claim drafting and claim construction that strong presumptions are afforded to standard transitional terms.

In Amgen Inc. v. Amneal Pharmaceuticals LLC,[1] the Federal Circuit reversed the district court’s construction of two Markush group limitations as closed to items other than those specifically listed.[2] With this reversal, the court remanded the case for a determination as to whether one of the accused products meets the correctly construed claim.[3]

Plaintiff Amgen filed suit against (1) Amneal Pharmaceuticals LLC and Amneal Pharmaceuticals of New York LLC (collectively, Amneal), (2) Piramal Healthcare UK Ltd. (Piramal), and (3) Zydus Pharmaceuticals (USA) Inc. and Cadila Healthcare Ltd. (collectively, Zydus) for infringement of US Patent No. 9,375,405 (the ’405 patent).[4] Specifically, after each defendant filed an Abbreviated New Drug Application (ANDA) for a generic version of Sensipar®, Amgen alleged that the proposed ANDA products would infringe the ’405 patent.[5]

The ’405 patent is directed to a rapid dissolution formulation of cinacalcet.[6] Representative claim 1 recites in relevant part:

1. 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;


(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 crospovidine, sodium starch glycolate, croscarmellose sodium, and mixtures thereof,… [7]


A critical issue below was construction of the binder and disintegrant Markush groups in elements (c) and (d), neither of which the parties sought to construe during claim construction.[8] It was not until Amgen’s proposed pretrial order that the claim construction issue came to a tee.[9] When Amgen argued that the Markush groups recited in elements (c) and (d) should be construed as open-ended, the district court disagreed. Relying on Multilayer Stretch Cling Film Holdings, Inc. v. Berry Plastics Corp., 831 F.3d 1350 (Fed. Cir. 2016), the court held that “Amgen ha[d] not overcome the very strong presumption that the Markush groups for the binder and disintegrant elements are closed to unrecited binders and disintegrants.”[10] Amgen moved for reargument, and the district court again rejected Amgen’s positions.[11]

Following a bench trial on infringement, the district court determined that Amneal does not infringe the asserted claims because, although Amneal uses a binder and disintegrant product falling within the respective Markush groups, it also uses a binder product and disintegrant product outside the Markush groups. Thus, Amneal’s product does not literally meet the binder and disintegrant claim limitations.[12] Amgen appealed the judgment of noninfringement as to Amneal.[13]


On appeal, Amgen challenged the district court’s holding that the binder and disintegrant Markush groups were closed to unrecited elements.

Amgen first pointed to the claim’s use of the term “comprising,” which it argued “renders the claim open-ended, even when other language restricts the scope of particular claim elements.”[14] Amgen next pointed to the phrase “at least one” found in the binder and disintegrant limitations, arguing that the “consisting of” term “only applies to the group from which ‘at least one’ binder or disintegrant must be selected.”[15]

Amgen also compared the use of “at least one” in the binder and disintegrant limitations to its absence in the Markush group of element (a) of the claim. As Amgen contended, this “at least one” language “would be meaningless if the groups are closed to additional binders and disintegrants and meaningless in view of the claim’s recitations of ‘mixtures thereof’ within the Markush group.”[16]

In response, Amneal, Piramal, and Zydus argued that the district court properly applied the Federal Circuit’s previous holding in Multilayer and that Amgen “failed to overcome the strong presumption that a claim term set off with ‘consisting of’ is closed to unrecited elements.”[17]

Reversing the district court’s construction, the Federal Circuit concluded that the defendants read more into Multilayer than was proper.[18] The Federal Circuit also addressed its previous opinion in Shire Development, LLC v. Watson Pharmaceuticals, Inc., 848 F.3d 981, 984 (Fed. Cir. 2017), which reiterated the “strong presumption” that a claim term introduced with “consisting of” is closed to unrecited elements, and held that the facts in this case were distinguishable.[19]

Looking at Multilayer, the Federal Circuit explained that the limitation at issue claimed “five identifiable inner layers, with each layer being selected from the group consisting of” and then recited a Markush group listing particular resins.[20] The only issue was the meaning of the “consisting of” language applicable to each layer, and the court “had no occasion to, and did not, consider the effect of [the “comprising”] transition phrase.”[21] Noting that the term “consisting of” creates a “very strong presumption that the claim element is ‘closed,’”[22] the Multilayer panel held this strong presumption was not overcome, and a product could not fall within the claim if it had resins outside the Markush group in the five identified layers.[23]

The Federal Circuit likewise found that Shire presented a similar construction issue. The claim included two Markush groups with “consisting of” language, and the court was not asked to, and did not, consider the impact of the transition phrase “comprising” in the claim.[24] As in Multilayer, the Shire panel determined that there was insufficient evidence to overcome the strong presumption that “consisting of” closed the Markush groups to additional elements.[25]

Distinguishing its previous decisions in Multilayer and Shire, the Federal Circuit in Amgen noted that the “decisive issue in this case is critically different.”[26] In particular, the court determined that there is “no language in Amgen’s claims indicating that every binder or disintegrant in the claimed formulation must be within the Markush groups, because the claim recites ‘at least one’ binder or disintegrant ‘selected from the group consisting of’ various excipients.”[27] Thus, “[t]he plain language of this claim requires ‘at least one’ of the Markush members and certainly does not indicate that the only binders and disintegrants in the claimed formulation are those listed in the groups.”[28]

According to the Federal Circuit, the patentee’s use of the transition phrase “comprising” further reinforces that additional binders and disintegrants not recited in the Markush group may be present in the claimed formulation.[29] As the court noted, the term “comprising” is “the standard transition term used to make clear that the claim does not preclude the presence of components or steps that are in addition to, though not inconsistent with, those recited in the limitations that follow.”[30] Accordingly, the claim’s plain language confirmed that the formulation must include at least one of the binders and disintegrants listed in the Markush group and may include unlisted binders and disintegrants.

Because the district court’s noninfringement holding for the Amneal product relied on its incorrect construction, the Federal Circuit vacated and remanded the infringement inquiry back to the district court.


The Federal Circuit’s opinion highlights the issues that may arise in using multiple transitional phrases throughout a claim. The opinion also reinforces the strong presumptions that must be overcome to interpret traditional transitional phrases in an atypical way. Whereas “comprising” is generally viewed as an open transitional term that permits the presence of unrecited elements, “consisting of” is generally viewed as a closed or partially closed transitional term that precludes the presence of unrecited elements in whole or in part. Courts will not disturb these well-accepted meanings absent clear indication in the intrinsic evidence that the patentee intended otherwise.


If you have any questions or would like more information on the issues discussed in this LawFlash, please contact the authors, Michael Abernathy, Christopher Betti, Maria Doukas, or Karon Fowler in our Chicago office, or any of the following lawyers from Morgan Lewis’s IP disputes team:

Joshua M. Dalton

Century City
Olga Berson, Ph.D.
Andrew V. Devkar
Seth M. Gerber

Wan-Shon Lo
Kevin P. Shortsle
Krista Vink Venegas, Ph.D.
Jason C. White
Amanda S. Williamson

C. Erik Hawes
David J. Levy
Rick L. Rambo

David W. Marston Jr. 

Eric Kraeutler

San Francisco
Brent A. Hawkins
Carla B. Oakley

Silicon Valley
Dion M. Bregman
Andrew J. Gray IV
Michael J. Lyons
Yalei Sun

Washington, DC
Natalie A. Bennett
Robert C. Bertin
Eric S. Namrow
Collin W. Park

John V. Gorman

[1] Nos. 2018-2414, 2019-1086, slip op. (Fed. Cir. Jan. 7, 2020).

[2] Id. at 19, 28.

[3] Id.

[4] Id. at 2.

[5] Id. at 3.

[6] Id.

[7] Id. at 4.

[8] Id. at 7 (emphasis added).

[9] Id.

[10] Id.

[11] Id.

[12] Id. at 8.

[13] Id. at 9. Amgen also appealed the judgment of noninfringement as to Piramal and Zydus cross-appealed the judgment of infringement. Id. at 9-10. This LawFlash addresses the claim construction issue only.

[14] Id. at 12.

[15] Id. at 12-13.

[16] Id. at 13.

[17] Id.

[18] Id.

[19] Id.

[20] Id. at 14-15 (emphasis added).

[21] Id. at 15.

[22] Id.

[23] Id.

[24] Id. at 17.

[25] Id.

[26] Id.

[27] Id. at 17-18.

[28] Id. at 18 (emphasis in original).

[29] Id.

[30] Id.