Last week, on April 18, 2018, Judge Stark in the District of Delaware entered the Final Judgment and Order dismissing the patent infringement case brought by Amgen Inc. and Amgen Manufacturing, Limited (collectively “Amgen”) against Coherus Biosciences, Inc. (“Coherus”). Judge Stark previously issued a Memorandum Order on March 26, 2018, adopting Magistrate Judge Burke’s Report and Recommendation (issued December 7, 2017) to grant Coherus’s motion to dismiss.

Amgen’s Complaint was filed on May 10, 2017, alleging infringement under the BPCIA due to Coherus’s submission of an abbreviated Biologic License Application seeking approval to market a biosimilar version of Amgen’s Neulasta® (pegfilgrastim) product. In particular, Amgen alleged infringement of a single patent, U.S. Patent No. 8,273,707 (“the ʼ707 patent”), directed to a process for purifying proteins. Of particular relevance, the claimed process requires a combination of a first and second salt selected from the group consisting of citrate and sulfate, citrate and acetate, and sulfate and acetate. Each salt must also be present within a particular concentration range. In its Complaint, Amgen alleged that the Coherus process met this limitation through the use of a first and second salt that is the equivalent of one or more of the specified salt pairs.

On June 1, 2017, Coherus filed a motion to dismiss for failure to state a claim. Coherus contended that it was entitled to dismissal because, as a matter of law, its accused manufacturing process does not infringe the ʼ707 patent. In particular, Coherus argued that its process does not utilize one of the claimed salt pair, and does not utilize salts within the claimed concentration range. Because the Court concluded that Coherus did not infringe based on the use of one of the claimed salt pairs, it did not address the second argument.

The Court initially noted that Amgen’s Complaint did not allege sufficient facts to support equivalence between the claimed salt pairs and the Coherus manufacturing process. Instead, the Court explained that Amgen’s Complaint simply makes the legal conclusion that there is equivalence. Normally, Amgen would likely be permitted an opportunity to amend its Complaint to include facts sufficient to support its doctrine of equivalents theory. However, Coherus argued there was no reason to allow Amgen to amend in this case because prosecution history estoppel barred Amgen’s theory of infringement. Specifically, Coherus argued that during prosecution Amgen distinguished its claims from the cited prior art by emphasizing that the prior art did not teach or suggest the particular combinations of salts that were being claimed. Accordingly, Coherus asserted that Amgen was estopped from asserting a different salt combination infringes the ʼ707 patent claims.

Following review of the prosecution history, the Court concluded that Amgen had clearly and unmistakably surrendered processes using a combination of salts that was different from the claimed combinations. In particular, the Court took note of Amgen’s repeated emphasis that the cited reference did not teach that the “particular combination” of salts would increase the dynamic capacity of the column as required by the then pending claims. Interestingly, the Court noted that if the prosecution history focused only on the fact that the pending claims required a combination of salts instead of the single salt disclosed in the prior art, there would not be an estoppel issue.

The Court also found it telling that Amgen did not substantively address the prosecution history argument made by Coherus. Instead, it made three “peripheral” arguments that the Court did not find persuasive. First, Amgen argued that Coherus’s argument regarding the salt pair limitation should be taken up after claim construction and discovery. However, the Court faulted Amgen for not explaining how either would “shed light on the objective inquiry regarding whether argument-based prosecution history estoppel applies here.” Second, Amgen argued that prosecution history does not apply to so-called clarifying amendments. Although the Court agreed with that principle, it noted that Amgen had not explained how the prosecution history statements Coherus relied on were clarifications as opposed to claim scope surrender. Third, Amgen argued Coherus had not met the stringent standard for applying argument-based estoppel. However, the Court dismissed this argument as being based on “wordplay [that] ignores the meat of Coherus’s position.”

It remains to be seen whether Amgen will appeal this ruling, although that seems likely. In related news, Coherus recently announced that it anticipates a U.S. commercial launch of its pegfilgrastim product in the second half of 2018.