945 F.3d 1368
Fed. Cir.2020Background
- Amgen owns U.S. Patent No. 9,375,405 directed to a rapid-dissolution cinacalcet HCl tablet; claim 1 recites % ranges for cinacalcet, a diluent (Markush list), a binder (Markush list, 1–5% by weight), and a disintegrant (Markush list, 1–10% by weight).
- Amneal, Piramal, and Zydus filed ANDAs for generic Sensipar®; Amgen sued for infringement; infringement was tried first (invalidity was bifurcated).
- During prosecution Amgen narrowed the cinacalcet dose range and accepted an Examiner’s Amendment converting binder and disintegrant limitations into Markush ("consisting of") group format; Examiner allowed the claims on the basis that the prior art did not disclose the claimed combination/amounts.
- The district court construed the binder and disintegrant Markush groups as closed (excluding unlisted excipients), found Amneal and Piramal noninfringing, and found Zydus infringing. The court barred Amgen’s equivalents arguments against Piramal by applying prosecution-history estoppel.
- On appeal the Federal Circuit held the district court erred in construing the binder/disintegrant limitations to exclude additional unrecited binders/disintegrants in a "comprising" claim that requires "at least one" listed binder/disintegrant; it vacated/remanded the Amneal noninfringement ruling, affirmed the Piramal noninfringement ruling (estoppel), and affirmed Zydus’s infringement finding.
Issues
| Issue | Plaintiff's Argument (Amgen) | Defendant's Argument | Held |
|---|---|---|---|
| Proper construction of binder/disintegrant Markush groups | "Comprising" + "at least one" means claim is open; unlisted binders/disintegrants may be present so long as at least one listed member meets the % requirements | "Consisting of" Markush groups create a strong presumption of closure; prosecution history shows narrowing | Claim construction reversed: Markush groups do not preclude additional unrecited binders/disintegrants in a comprising claim so long as at least one listed member satisfies the weight-range limitation |
| Literal infringement of binder limitation (Amneal/Opadry) | Opadry contains HPMC (a listed binder); presence of HPMC in the Opadry composite satisfies the binder limitation (if present in 1–5%) | Opadry is a composite product different from HPMC alone; district court’s analysis treated Opadry as not literally the listed binder | Reversed: HPMC present in Opadry meets the listed binder limitation in principle; district court’s analysis focusing on compositional differences was legally erroneous and remand required to assess % present |
| Doctrine of equivalents / prosecution-history estoppel (Piramal/pregelatinized starch) | The Examiner’s Amendment was not made for patentability reasons (Amgen later said it was formatting/clarifying); equivalents for pregelatinized starch should be available | Examiner’s Amendment and prior rejections indicate narrowing for patentability; Amgen surrendered equivalents; estoppel bars claiming pregelatinized starch as equivalent | Affirmed: Amgen failed to show the Examiner’s Amendment was unrelated to patentability; prosecution-history estoppel bars equivalents to capture unlisted binders like pregelatinized starch |
| Zydus: function of pregelatinized starch (diluent vs binder) and infringement | Pregelatinized starch can act as a binder (fractions theory) so Zydus’s product may not literally meet diluent limitation | Zydus’s ANDA and expert testimony identified its starch as a diluent; district court credited that and found literal infringement | Affirmed: district court did not clearly err in crediting evidence (including Zydus’s ANDA) that its pregelatinized starch functions as a diluent, so Zydus infringes |
Key Cases Cited
- Multilayer Stretch Cling Film Holdings, Inc. v. Berry Plastics Corp., 831 F.3d 1350 (Fed. Cir. 2016) (explains strong presumption that "consisting of" Markush groups are closed and the standard for overcoming that presumption)
- Shire Dev., LLC v. Watson Pharm., Inc., 848 F.3d 981 (Fed. Cir. 2017) (applies Multilayer presumption to pharmaceutical Markush lists)
- Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722 (2002) (establishes prosecution-history estoppel limits on doctrine of equivalents)
- Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 520 U.S. 17 (1997) (patentee bears burden to show an amendment was for reasons unrelated to patentability)
- Teva Pharm. USA, Inc. v. Sandoz, Inc., 574 U.S. 318 (2015) (claim construction is a legal question that may involve subsidiary facts)