IP Law Daily Amgen barred from asserting Neulasta patent against generic competitor
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Monday, July 29, 2019

Amgen barred from asserting Neulasta patent against generic competitor

By Cheryl Beise, J.D.

Prosecution history estoppel barred Amgen from succeeding on its infringement claim against Coherus BioSciences under the doctrine of equivalents.

The federal district court in Wilmington, Delaware, did not err in dismissing Amgen’s infringement suit against Coherus BioSciences, in connection with the latter company’s plan to market a biosimilar version of Amgen’s pegfilgrastim product Neulasta, the U.S. Court of Appeals for the Federal Circuit has ruled. During prosecution of the asserted patent, Amgen clearly surrendered ground involving combinations of salts other than those specifically claimed (Amgen Inc. v. Coherus BioSciences Inc., July 29, 2019, Stoll, K.).

Amgen Inc. and Amgen Manufacturing Ltd. (collectively, "Amgen") sell a pegfilgrastim product under the brand name Neulasta. Pegfilgrastim is a recombinant therapeutic protein that stimulates the production of neutrophils, a type of white blood cell. In connection with Neulasta, Amgen owns U.S Patent No. 8,273,707 (the ’707 patent), which claims methods of purifying proteins using hydrophobic interaction chromatography (HIC). A HIC column contains a solid, hydrophobic matrix and "is used to separate proteins on the basis of hydrophobic interactions between the hydrophobic moieties of the protein and insoluble, immobilized hydrophobic groups on the matrix."

In August 2016, Coherus filed an abbreviated Biologic License Application (aBLA) seeking Food and Drug Administration approval to market a biosimilar version of Neulasta. In May 2017, Amgen sued Coherus for infringing the ’707 patent based on Coherus’s aBLA. Amgen alleged infringement under the doctrine of equivalents because the salt combination used in Coherus’s process did not match any of the three salt combinations expressly claimed in the ’707 patent. A magistrate judge recommended that prosecution history estoppel barred Amgen’s suit against Coherus because Amgen was "attempting to reassert surrendered ground involving other combinations of salts." The district court adopted the magistrate judge’s report and granted Coherus’s motion to dismiss based on prosecution history estoppel. The district court further found that the dedication-disclosure doctrine formed an independent basis for dismissal. The district court reasoned that by disclosing but not claiming the salt combination used by Coherus, Amgen had dedicated that particular combination to the public. Amgen appealed.

Prosecution history. During prosecution of the ’707 patent, the examiner rejected the then-pending claims as obvious in view of U.S. Patent No. 5,231,178 ("Holtz"). The examiner noted that Holtz disclosed several salts for improving hydrophobic interactions between a protein and the column matrix. Amgen responded to the examiner’s rejection, pointing out that "the pending claims recite a particular combination of salts." All of the ’707 claims require a salt combination chosen from one of three pairs: citrate and sulfate, citrate and acetate, or sulfate and acetate. The examiner again rejected the claims. Amgen replied to the examiner’s second rejection and reiterated that Holtz does not disclose a combination of salts and does not disclose enhancing the dynamic capacity of a HIC column. Amgen pointed out that choosing a working salt combination was a "lengthy development path" and that "merely adding a second salt" would not result in the invention. The examiner then allowed the claims.

Estoppel. Prosecution history estoppel prevents a patentee from using the doctrine of equivalents to recapture subject matter surrendered from the literal scope of a claim during prosecution. Prosecution history estoppel can occur by (1) making a narrowing amendment to the claim (amendment-based estoppel) or (2) by surrendering claim scope through argument to the patent examiner (argument-based estoppel).

Based on the record, the Federal Circuit agreed with the district court that "argument-based prosecution history estoppel applies here because Amgen clearly and unmistakably surrendered unclaimed salt combinations during prosecution." To overcome the examiner’s rejection, Amgen distinguished Holtz on the basis that Holtz did not teach or suggest the "particular combinations of salts" recited in Amgen’s claim. "Indeed, Amgen emphasized ‘particular’ and referred to its particular salts three times in the span of two pages," the court noted. Amgen also attached to its response a declaration of the ’707 patent’s inventor that highlighted and discussed the same particular combinations recited in the patent’s claims. The Federal Circuit agreed with the district court’s conclusion that "a competitor would reasonably believe" that Amgen surrendered unclaimed salt combinations.

While Amgen did assert multiple reasons for why Holtz was distinguishable, the Federal Circuit said that its precedent instructs that estoppel can attach to each argument. "Amgen did not rely on the combination of its asserted grounds to distinguish Holtz, so prosecution history estoppel applies to the ‘particular combinations’ ground regardless of the other two arguments Amgen made," the court said. It also did not matter that Amgen did not make the disqualifying argument in its last response to the patent examiner. Amgen’s prior statements were not erased. "There is no requirement that argument-based estoppel apply only to arguments made in the most recent submission before allowance," the court said.

The Federal Circuit concluded that the district court did not err in determining that prosecution history estoppel barred Amgen from succeeding on its infringement claim against Coherus under the doctrine of equivalents. The appeals court affirmed dismissal of Amgen’s complaint for failure to state a claim and did not reach the issue of whether Amgen dedicated unclaimed salt combinations to the public.

This case is No. 18-1993.

Attorneys: Nicholas P. Groombridge (Paul, Weiss, Rifkind, Wharton & Garrison LLP) for Amgen Inc. and Amgen Manufacturing Ltd. Bradford Peter Lyerla (Jenner & Block LLP) for Coherus BioSciences, Inc.

Companies: Amgen Inc.; Amgen Manufacturing Ltd.; Coherus BioSciences, Inc.

MainStory: TopStory Patent FedCirNews

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