On November 12, 2025, Regeneron filed a Motion to Strike Certain Affirmative Defenses and Dismiss Certain Counterclaims against Amgen in the aflibercept patent litigation in the U.S. District Court for the Northern District of West Virginia.
The dispute centers on Amgen’s aflibercept biosimilar, PAVBLU®. As we have previously reported, in March 2025, the U.S. Court of Appeals for the Federal Circuit affirmed the district court’s denial of Regeneron’s motion for a preliminary injunction in the ongoing litigation concerning U.S. Patent No. 11,084,865. Amgen then launched the product in October 2024. In June 2025, Regeneron filed a new suit against Amgen, asserting the newly issued U.S. Patent No. 12,331,099 (“the ’099 patent”). 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.
In its recent Motion, Regeneron moved to strike the following counterclaims: unclean hands, laches, inequitable conduct, and patent misuse. Regeneron also moved to dismiss Amgen’s counterclaims of laches, inequitable conduct, patent misuse, antitrust, and its California Unfair Competition Law (“UCL”) counterclaim. According to Regeneron, Amgen’s defenses are a “kitchen-sink approach” with “Strangelovian nonchalance” toward Federal Circuit precedent.
I. Inequitable Conduct
Amgen had asserted in its Answer that the ’099 patent is unenforceable due to inequitable conduct because Regeneron’s counsel misrepresented to the PTO that the inventors of the ’865 patent also invented the subject matter claimed in the ’099 patent and by falsely “asserting that the claims of the ’099 [p]atent did not present new matter beyond the description in the originally filed application.” Br. at 15.
As Regeneron notes, the Federal Circuit has described inequitable conduct as the “atomic bomb” of patent litigation, as patent owners may face severe consequences if the entire patent is rendered unenforceable. Challenging Amgen’s inequitable conduct defense and counterclaim, Regeneron argues that Amgen’s Answer “inject[s] chaos into this already-complicated MDL” and “presents a bizarre picture of inequitable conduct law” and that Amgen’s counterclaims lack sufficient facts to state a plausible claim to relief. Id. at 2. Regeneron contends that Amgen has not satisfied the heightened pleading requirement mandated by Fed. R. Civ. P. 9(b) for inequitable conduct claims and other fraud-based claims. See id. at 4; Fed. R. Civ. P. 9(b) (“In alleging fraud or mistake, a party must state with particularity the circumstances constituting fraud or mistake.”). Regeneron also insists that Amgen’s inventorship theory “proceeds directly from its misreading of the claims.” Id. at 11. Regeneron argues that Amgen’s reduction to practice of a different, “buffer-free” species within the genus described and claimed in the ’099 patent “does not make Amgen an inventor on the ’099 patent—it makes Amgen an infringer.” Id. at 12.
Finally, on the “no new matter” theory, Regeneron argues that “Amgen’s final inequitable conduct theory is an impermissible repackaging of its written-description invalidity position.” Id. at 15. Regeneron states that although Amgen argues that the ’099 patent claims lack adequate written-description support, “such disagreement does not establish or reasonably suggest Regeneron’s counsel knew the claims lack support or offered its ‘no new matter’ argument with an intent to deceive.” Br. at 16. Regeneron also contends that the “no new matter” theory could not have been material to the issuance of the ’099 patent claims because the examiner possessed all relevant information to make a determination. See id. at 17.
II. Antitrust and Other Counterclaims
Coupled with its inequitable conduct claims, Amgen also raised antitrust counterclaims for monopolization based on alleged fraud in the procurement and assertion of the ’099 patent and twelve other patents. In response, Regeneron argues that no fraud occurred in the procurement of the ’099 patent or the twelve others, and none of Amgen’s alleged losses relating to the patents are “antitrust injuries” attributable to Regeneron. See id. at 17–18. To this point, Regeneron invokes the purpose of the BPCIA, noting that the patent dance framework under the BPCIA affords biosimilar applicants like Amgen “substantial control over the scope of the first phase of litigation,” and thus, Amgen’s claim for antitrust injuries in the form of litigation costs should fail. See id. at 21.
Regeneron argues that Amgen’s claims under the California UCL arise from the same conduct underlying its federal antitrust claims and should be dismissed for the same reasons. Further, Regeneron argues that laches is inapplicable, and that the patent misuse and equitable doctrines defenses are inadequately pled.
Stay tuned to Big Molecule Watch as we continue to monitor updates in the biosimilars industry.