Federal Circuit Agrees That Argument-Based Prosecution Estoppel Barred Amgen from Succeeding on Infringement Claim

“Where a patentee asserts multiple bases for distinguishing the prior art during prosecution, each separate argument can create a separate prosecution estoppel if it shows a clear and unmistakable surrender of subject matter and as long as the prior art was not distinguished based on the combination of these various grounds.”

The Federal Circuit issued an opinion on July 29 affirming the District Court for the District of Delaware’s dismissal of Amgen Inc. and Amgen Manufacturing Ltd.’s (collectively, “Amgen”) complaint alleging infringement of U.S. Patent 8,273,707 (the “’707 Patent”) for failure to state a claim. The district court held that prosecution history estoppel barred Amgen from succeeding on its infringement claim under the doctrine of equivalents. Amgen Inc. v. Coherus BioSciences, Inc., No. 18-1993 (Fed Cir. July 29, 2019) (Before Reyna, Hughes, and Stoll, Circuit Judges) (Opinion for the Court, Stoll, Circuit Judge).

The ’707 Patent is directed to methods of purifying proteins using hydrophobic interaction chromatography (“HIC”). Purification from contaminants allows proteins to be therapeutically useful.  Claim 1 recites:

  1. A process for purifying a protein on a hydrophobic interaction chromatography column such that the dynamic capacity of the column is increased for the protein comprising

mixing a preparation containing the protein with a combination of a first salt and a second salt,

loading the mixture onto a hydrophobic interaction chromatography column, and eluting the protein,

wherein the first and second salts are selected from the group consisting of citrate and sulfate, citrate and acetate, and sulfate and acetate, respectively, and

wherein the concentration of each of the first salt and the second salt in the mixture is between about 0.1 M and about 1.0.

Prosecution History

During prosecution, the examiner repeatedly rejected the claims as obvious in view of U.S. Patent 5,231,178 (“Holz”). In response, Amgen distinguished the ‘707 Patent based on the particular combination of salts claimed. Amgen argued that Holz did not teach or suggest any combinations of salts or the particular combinations of salts claimed in the ‘707 Patent. Amgen presented additional arguments, including that Holz did not teach dynamic capacity at all while the claimed invention was directed to increasing the dynamic capacity of a HIC column. In her declaration, the inventor explained and highlighted that the particular salt combinations claimed in the ‘707 Patent resulted in significant improvements over prior art, including increases in the dynamic capacity.

After Coherus filed an abbreviated Biologic License Application (aBLA) seeking approval to market a biosimilar version of an Amgen product, and the aBLA revealed that Coherus’s manufacturing process contained steps used to purify a protein using a salt combination, although not the one recited in Amgen’s claims, Amgen sued for patent infringement. The district court granted Coherus’ motion to dismiss, holding, first, that Amgen clearly and unmistakably surrendered salt combinations other than the particular combinations recited in the ‘707 Patent during prosecution, and, second, that Amgen had dedicated the particular combination used by Coherus to the public by disclosing but not claiming it.  The court thus dismissed Amgen’s complaint for failure to state a claim.  The Federal Circuit affirmed.

Clear and Unmistakable

“Prosecution history estoppel applies as part of an infringement analysis to prevent a patentee from using the doctrine of equivalents to recapture subject matter surrendered from the literal scope of a claim during prosecution[].” Argument-based estoppel, at issue in this appeal, can occur “by surrendering claim scope through argument to the patent examiner” and exists where prosecution history shows “a clear and unmistakable surrender of subject matter.” Here, Amgen clearly and unmistakably surrendered unclaimed salt combinations during prosecution, said the court.  In its initial response, Amgen distinguished the prior art on the basis that the prior art did not teach or suggest the “particular combinations of salts” recited in the ‘707 Patent.  Furthermore, both in its response and accompanying Declaration, Amgen repeatedly discussed the particular combination of salts claimed without mentioning any others. Amgen’s response concluded by specifically emphasizing that “[u]se of this particular combination of salts greatly improves the cost-effectiveness of commercial manufacturing.” A competitor would reasonably believe that Amgen surrendered unclaimed salt combinations.

The fact that Amgen asserted three separate bases for distinguishing the prior art during prosecution, only one of which was relevant here, did not obviate the Court’s conclusion. “[W]here a patent applicant sets forth multiple bases to distinguish between its invention and the cited prior art, the separate arguments [can] create separate estoppels as long as the prior art was not distinguished based on the combination of these various grounds.” Here, Amgen did not rely on a combination of the asserted grounds to distinguish the prior art.

Similarly, the fact that Amgen’s response to the examiner, which resulted in the allowance of the claims, did not contain the “particular combinations” argument was inapposite. No requirement exists that argument-based estoppel apply only to arguments made in the submission immediately preceding allowance. In fact, “[c]lear assertions made during prosecution in support of patentability, whether or not actually required to secure allowance of the claim, may also create an estoppel.” Here, Amgen repeatedly emphasized the particular combination of salts claimed and could not now recapture the surrendered subject matter, said the opinion. Because prosecution estoppel barred Amgen from succeeding on its infringement claim under the doctrine of equivalents, its complaint was dismissed.



The Author

Brandon Reed

Brandon Reed is an Associate at Troutman Sanders. His practice focuses on all areas of patent prosecution and litigation, spanning a variety of technology fields.

For more information or to contact Brandon, please visit his Firm Profile Page.

Brandon Reed

Majda Muhic is an Associate at Troutman Sanders. She helps clients navigate a wide range of intellectual property issues under both federal and state law. Her practice focuses primarily on intellectual property litigation and related strategic counseling. She has counseled clients in proceedings in federal district and appellate courts as well as before the Patent Trial and Appeal Board and the Trademark Trial and Appeal Board (TTAB). Majda’s experience covers a variety of industries and technologies, including pharmaceuticals, consumer products and electronics, and motorized winches. In addition to patent litigation, she has successfully counseled clients in trademark, trade dress, trade secret and copyright infringement matters.

For more information or to contact Majda, please visit her Firm Profile Page.

Brandon Reed

Robert Schaffer is an intellectual property partner at Troutman Sanders. Bob applies more than 30 years of experience to IP counseling and litigation. His work includes patent procurement, strategic planning and transactional advice, due diligence investigations, district court patent cases, and Federal Circuit appeals. He regularly handles complex and high-profile domestic and international patent portfolios, intellectual property agreements and licensing, IP evaluations for collaborations, mergers, and acquisitions. In disputed court cases Bob’s work includes representing and counseling client in ANDA litigations, complex patent infringement cases and appeals, and multidistrict and international cases. In disputed Patent Office matters his work includes representing and counseling clients in interferences, reexaminations, reissues, post-grant proceedings, and in European Oppositions. For more information and to contact Bob please visit his profile page at the Troutman Sanders website.

Brandon Reed

Dustin Weeks is a Partner in the intellectual property practice group at Troutman Sanders. His practice spans all areas of intellectual property law, including patent prosecution, patent litigation (including Hatch-Waxman litigation), and client counseling. He represents clients ranging from start-ups and solo inventors to Fortune 500 companies. Dustin works closely with his clients to learn their business objectives so that he can tailor strategies to procure, protect, and enforce their intellectual property. Dustin specializes in post-grant proceedings (e.g. Inter Partes Reviews) before the Patent Trial and Appeal Board (PTAB) where he has extensive experience representing both patent owners and petitioners across a wide range of technologies, including wireless networking, pharmaceuticals, MEMs devices, medical devices, and electro-mechanical consumer devices. Dustin's broad experience in patent prosecution, counseling, and patent litigation uniquely positions him to navigate the blended practice of post-grant proceedings.

For more information or to contact Dustin, please visit his Firm Profile Page.

Brandon Reed

Joseph Robinson has over 20 years of experience in all aspects of intellectual property law. He focuses his practice in the pharmaceutical, life sciences, biotechnology, and medical device fields. His practice encompasses litigation, including Hatch-Waxman litigation; licensing; counseling; due diligence; and patent and trademark prosecution. He has served as litigation counsel in a variety of patent and trademark disputes in many different jurisdictions, and has also served as appellate counsel before the Court of Appeals for the Federal Circuit. Joe also focuses on complex inter partes matters before the U.S Patent and Trademark Office, inventorship disputes, reexaminations and reissues. His experience includes numerous interferences, a particular advantage in new U.S. Patent and Trademark Office post-grant proceedings. He also counsels on patent–related U.S. Food and Drug Administration issues, including citizen petitions, Orange Book listing, and trademark issues. For more information and to contact Joe please visit his profile page at the Troutman Sanders website.

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There are currently 1 Comment comments.

  1. TFCFM August 22, 2019 10:20 am

    This is, of course, why one of the first steps in training a new patent agent/associate for prosecution is to give them a Miranda-like warning:

    Anything you say may be used against you…

    (THEN, you can “book” them, preferably with the MPEP.)