Opinion ID: 4469830
Heading Depth: 2
Heading Rank: 4

Heading: Piramal’s Product

Text: Amgen challenges the district court’s noninfringement finding for Piramal for a different reason: the court’s application of prosecution history estoppel. Piramal’s product uses pregelatinized starch as a binder, which is not listed in the binder Markush group of claim 1. Amgen therefore argues under the doctrine of equivalents that pregelatinized starch has a native starch fraction that functions as a diluent and a cold water soluble fraction that functions as a binder. The doctrine of equivalents is well-established in our jurisprudence. See Eli Lilly & Co. v. Hospira, Inc., 933 F.3d 1320, 1329 (Fed. Cir. 2019) (collecting cases). While “[t]he scope of a patent is not limited to its literal terms but instead embraces all equivalents to the claims described,” Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 732 (2002), prosecution history estoppel acts as a “legal limitation” on the doctrine, Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 520 U.S. 17, 30 (1997). “Estoppel arises when an amendment is made to secure the patent and the amendment narrows the patent’s scope.” Festo, 535 U.S. at 736. The burden falls on the patentee to “demonstrate[] that an amendment required during 22 AMGEN INC. v. AMNEAL PHARMACEUTICALS LLC prosecution had a purpose unrelated to patentability.” Warner-Jenkinson, 520 U.S. at 40–41. “Where the [patentee] is unable to establish such a purpose, a court should presume that the purpose behind the required amendment is such that prosecution history estoppel would apply.” Id. at 41. The district court rejected Amgen’s doctrine of equivalents argument as barred by prosecution history estoppel. During prosecution, the examiner rejected Amgen’s claims for obviousness, and, in response, Amgen narrowed the amount of cinacalcet in the claim in an attempt to overcome the rejection. In the court’s view, Amgen tried but “failed” to overcome the obviousness rejection. Decision, 328 F. Supp. at 392. The court noted that the Examiner did not allow the claims following this amendment, but, instead, proposed the Examiner’s Amendment adding Markush groups to the binder and disintegrant limitations. The court opined that “[t]here would have been no need for the Examiner to propose an amendment if Amgen’s [Ci- nacalcet] Amendment was sufficient.” Id. Moreover, the court noted that the Examiner stated that the claims were being allowed because the closest prior art failed to disclose or render obvious the “combination of components and in the amounts” in the claim. Id. at 392–93. The court understood these statements in the prosecution history to indicate that the Examiner’s Amendment was entered for substantial reasons relating to patentability. Amgen first argues that the presumption of estoppel does not apply here because it did not narrow the binder or disintegrant limitations for reasons of patentability. Instead, it submits that the Cinacalcet Amendment alone was necessary to rebut the prior art. Amgen Br. 47. Amgen points to the absence of any statements by the Examiner about the Markush groups in particular and Amgen’s own later statement in the second Request for Continued Examination that the language added by the Examiner was not added in “response to a prior art AMGEN INC. v. AMNEAL PHARMACEUTICALS LLC 23 rejection but rather to place the claims in proper format and to better define the claimed subject matter, including equivalents.” Amgen Br. 49 (quoting J.A. 10707). Even if the presumption of estoppel applies, however, Amgen argues that it is overcome because the Markush limitations were added for reasons other than patentability. Amgen argues that the Examiner’s Amendment simply explained in more explicit terms and clarified the composition that the claims already covered. Because the Markush groups and treatment limitations were already present in previously rejected dependent claims, Amgen argues that a person of skill would have understood from the intrinsic record that the Examiner’s Amendment was not related to patentability. According to Amgen, the amendment could not have distinguished Creekmore or Hsu because those references already disclosed the excipients in the Markush groups. Piramal responds that Amgen’s acceptance of the Examiner’s Amendment led directly to the allowance of the claims. Amneal & Piramal Br. 49. According to Piramal, Amgen’s statement during prosecution that its amendment was not in response to a prior art rejection was self-serving and is irrelevant to whether a claim amendment was made for reasons of patentability. Id. at 50. In Piramal’s view, the Examiner’s Amendment was substantial and narrowed the claims, so it could not be considered a clarifying amendment. Piramal also argues that the addition of the Markush groups overcame the obviousness rejection. Piramal reads Creekmore to disclose 152 binder-disintegrant combinations and Hsu discloses 120 combinations. Thus, Piramal submits that the narrowed range of excipient combinations in the Examiner’s Amendment—which would include only 12 disintegrant-binder combinations—overcame Creekmore and Hsu because the amended claim recited a smaller set of members within the group. Id. at 54. 24 AMGEN INC. v. AMNEAL PHARMACEUTICALS LLC We agree with Piramal that Amgen’s doctrine of equivalents argument is barred by prosecution history estoppel. Amgen amended its claims in two ways during prosecution—first narrowing the amount of cinacalcet to a range of 20 mg to 100 mg and second, accepting an Examiner’s Amendment that revised the claim’s disintegrant and binder limitations to be in Markush group format. Amgen urges that only the first of these amendments, the Cinacalcet Amendment, was adopted for a substantial reason relating to patentability. But if Amgen is correct that its narrowing of the cinacalcet limitation was sufficient to secure allowance, the Examiner proposed the Examiner’s Amendment for no purpose at all. Such a reading of the prosecution history is at best unpersuasive. Amgen also points to its statement in its second Request for Continued Examination that the Examiner’s Amendment was added “to place the claims in proper format and to better define the claimed subject matter.” Amgen Br. 49 (citing J.A. 10707). But this statement was made over eight months after the Examiner’s Amendment was accepted and the claims were allowed. It is unclear what, if any, insight this conventional boilerplate statement provides into the reasons for the Examiner’s Amendment. We therefore conclude that Amgen failed to carry its burden to demonstrate that the Examiner’s Amendment was made for a reason unrelated to patentability. We thus agree that Amgen surrendered equivalent but unclaimed binders and disintegrants. Warner-Jenkinson, 520 U.S. at 41. It is estopped to claim equivalence to remedy a failure of the accused product to meet the Markush limitations. As a final argument, Amgen suggests that the tangential exception to prosecution history estoppel applies. However, Piramal uses pregelatinized starch as a binder, a use taught by Creekmore and Hsu. “[A]n amendment made to avoid prior art that contains the equivalent in question is AMGEN INC. v. AMNEAL PHARMACEUTICALS LLC 25 not tangential.” Intervet Inc. v. Merial Ltd., 617 F.3d 1282, 1291 (Fed. Cir. 2010).