As we previously reported, on June 17, 2025, Regeneron filed a complaint against Amgen under the BPCIA, alleging that Amgen’s aflibercept biosimilar, PAVBLU, infringes U.S. Patent No. 12,331,099 (“the ’099 patent”). The ‘099 patent issued on June 17, 2025, almost eight months after Amgen announced the launch of PAVBLU on October 30, 2024. Last week, on September 12, Amgen responded to Regeneron’s complaint, firing back with fourteen affirmative defenses, including inequitable conduct and patent misuse, and counterclaims for declaratory judgments of non-infringement, invalidity, and unenforceability due to prosecution laches, inequitable conduct, and patent misuse, as well as Sherman Act antitrust “Walker Process” fraud claims and a counterclaim of unfair competition under California law.
Prosecution Laches: Amgen argues that Regeneron committed prosecution laches by delaying 18 years to file the application that led to the ‘099 patent, which claims priority to a provisional application filed on June 16, 2006. According to Amgen, though the ’099 patent claims a “buffer-free” formulation of aflibercept, all previous Regeneron patents required a “separate buffer.” Amgen argues that it was prejudiced by this unreasonable delay, during which it “invested significant resources” in developing its buffer-free PAVBLU formulation.
Inequitable Conduct: Amgen further alleges that Regeneron committed inequitable conduct in the prosecution of the ‘099 patent by misrepresenting the inventors of the patent, failing to disclose to the Patent Examiner that the claims encompassed new matter, and disclosing information in a manner that was intended to deceive the Patent Office.
According to Amgen, Regeneron’s counsel knew that the listed inventors did not invent any buffer-free aflibercept formulations, but nonetheless Regeneron’s counsel resubmitted inventor declarations signed in February 2014 that had accompanied a related application that did not claim a buffer-free formulation. Amgen further alleges that Regeneron’s counsel “were aware that employees of Amgen, not Regeneron, were the true inventors of buffer-free aflibercept formulations.” Additionally, Amgen alleges that Regeneron delayed in disclosing information about the earlier PAVBLU litigation until after receiving a notice of allowance for the ’099 Patent.
Amgen also alleges that the prosecution history of the ’009 patent demonstrates Regeneron had a “specific intent to deceive the USPTO.” According to Amgen, Regeneron waited eighteen years to “seek to obtain the claims of the ’099 patent,” but then filed the application for the ’099 patent one day after the U.S. Court of Appeals for the Federal Circuit declined to enjoin Amgen from marketing PAVBLU pending appeal of the U.S. District Court for the District of West Virginia’s denial of a preliminary injunction. Further, Amgen alleges that Regeneron requested “expedited examination under the Patents for Humanity Program” despite having “specific knowledge of Amgen’s invention of a buffer-free aflibercept formulation.”
In addition, Amgen alleges that Regeneron “delayed in disclosing information relating to” the ongoing aflibercept litigation with Amgen and Amgen’s development of a buffer-free formulation. According to Amgen, on the date Regeneron filed the application and on January 20, 2025, when Regeneron responded to an Office Action, Regeneron was aware of but submitted no information regarding “(i) the ongoing litigation between Regeneron and Amgen; (ii) the September 2024 Order Denying PI; (iii) the publicly available label for Amgen’s [PAVBLU] product; (iv) the identity of the components in Amgen’s [PAVBLU] product; and (v) Amgen’s ’463 Application relating to buffer-free aflibercept formulations published in October 2020.” On February 17, 2025, eleven days after the Examiner signed a Notice of Allowance, Regeneron submitted an Information Disclosure Statement (“IDS”) that contained “over 600 references,” but still did not disclose these five items. The next day, Regeneron submitted a second IDS that disclosed other court proceedings involving the same patent at issue in the ongoing aflibercept litigation with Amgen, but still did not disclose the five listed items.
According to Amgen, on March 14, 2025, “the Federal Circuit concluded” that “it was Amgen, not Regeneron, that pioneered the invention of buffer-free therapeutic protein formulations.” However, Amgen alleges that Regeneron did not submit this decision to the USPTO until April 3, 2025, a day after Regeneron had paid the issue fee for the ’099 patent, and as a part of “a Quick Path Information Disclosure Statement” that contained “other voluminous Court decisions, including decisions favorable to Regeneron that concerned buffer-containing aflibercept formulations (not buffer-free aflibercept formulations) that were previously disclosed” by the February 18, 2025 IDS. According to Amgen, these actions in the prosecution of the ‘’099 patent demonstrate both Regeneron’s material misrepresentation to the USPTO and specific intent to deceive.
Patent Misuse: In support of its patent misuse argument, Amgen states that “Regeneron impermissibly broadened the scope of the ’099 Patent to include claims that Regeneron knew to be invalid” and pursued buffer-free claims “despite knowing that (i) the listed inventors on the ’099 Patent did not invent buffer-free ophthalmic formulations comprising a VEGF antagonist; and (ii) the specification contains no disclosures supporting such an invention.”
Antitrust Claims: In making its Walker Process fraud claims, Amgen alleges that the twelve patents asserted by Regeneron in the earlier litigation were also obtained through fraud and deliberate omissions, and that this fraud has allowed Regeneron to maintain supracompetitive prices and profits for 2 mg EYLEA. Amgen asserts that Regeneron has had monopoly power in the market for 2 mg aflibercept-based treatments. Amgen claims that it has “suffered and will continue to suffer injuries that the antitrust laws were designed to prevent and that flow directly from Regeneron’s anticompetitive conduct.”
Unfair Competition: Finally, in Amgen’s eighth counterclaim, it argues that Regeneron’s conduct “violates California’s Unfair Competition Law, Cal. Bus. & Prof. Code §§ 17200, et seq., which prohibits any unlawful, unfair or fraudulent business act or practice.”
Stay tuned to Big Molecule Watch as we continue to monitor this litigation.