Antitrust Law Daily Wrap Up, ANTITRUST—N.D.W. Va.: Amgen laches defense survives in Regeneron Eylea biosimilar patent MDL, (Jul 8, 2026)

By Martin A. Steinberg, J.D.

Amgen’s claim that Regeneron fraudulently procured and asserted Eylea-related patents was largely dismissed, but its prosecution-laches theory survived.

The federal district court in Clarksburg, West Virginia, granted in part a motion by Regeneron Pharmaceuticals, Inc. to strike Amgen Inc.’s defenses and dismiss counterclaims in multidistrict patent litigation over Eylea biosimilars. Amgen had asserted inequitable conduct, antitrust, California Unfair Competition Law (UCL), prosecution laches, patent misuse, and unclean-hands theories based on Regeneron’s procurement and assertion of the ’099 patent and other patents. The court dismissed with prejudice Amgen’s inequitable conduct, patent misuse, and unclean-hands theories, and dismissed its antitrust and UCL counterclaims with prejudice as to the ’099 patent. However, the court dismissed, without prejudice, the antitrust and UCL theories tied to earlier 2024 patent litigation and allowed Amgen’s prosecution-laches defense and counterclaim to proceed (In Re: Aflibercept Patent Litigation, No. 1:24-md-03103-TSK-JPM (N.D.W. Va. Jul. 7, 2026)).

Background. Regeneron Pharmaceuticals, Inc. is a biotechnology company known for developing ophthalmic and immunology-related drugs. One of its principal products, Eylea, is an anti-vascular endothelial growth factor drug used to treat wet age-related macular degeneration, diabetic macular edema, and other retinal conditions.

Amgen Inc. is a global biotechnology company that developed ABP 938 as a proposed biosimilar to Eylea. Amgen submitted an abbreviated Biologics License Application to the U.S. FDA in August 2023, and the FDA approved the biosimilar in 2024 for commercial launch under the brand name Pavblu. Unlike Eylea, ABP 938 does not contain a separate buffer component; instead, Amgen’s formulation allegedly uses the VEGF antagonist itself for buffering.

Regeneron first sued Amgen in January 2024 in the Central District of California, alleging infringement of 32 patents related to Eylea after Amgen submitted an abbreviated Biologics License Application for ABP 938. That case was later consolidated with other Eylea biosimilar cases in the multidistrict litigation pending in the Northern District of West Virginia. The court previously denied Regeneron’s motion for a preliminary injunction against Amgen, and the Federal Circuit affirmed, with both decisions relying on the fact that Amgen’s accused formulation lacked a separate buffer required by the asserted claims.

In June 2025, Regeneron filed the present action asserting U.S. Patent No. 12,331,099, which was also consolidated into the MDL. In response, Amgen alleged inequitable conduct in the procurement of the ’099 patent; antitrust violations arising from Regeneron’s assertion of the ’099 patent and 12 earlier patents that had been asserted but later dropped; and additional defenses and counterclaims, including laches, patent misuse, and unclean hands.

Inequitable conduct. The court granted Regeneron’s motion as to Amgen’s inequitable conduct defense and counterclaim. Amgen’s inequitable conduct defense and counterclaim alleged that Regeneron fraudulently procured the 2024 litigation patents and the later-issued ’099 patent. The court explained that inequitable conduct requires a showing that the patent applicant misrepresented or omitted material information with a specific intent to deceive the PTO, and that the alleged misconduct must be pleaded with particularity under Rule 9(b), including the “who, what, when, where, and how” of the alleged misrepresentation or omission.

Amgen relied on two alleged misrepresentations. First, it claimed that Regeneron submitted false inventorship declarations for the ’099 patent because that patent claimed an aflibercept formulation without a separate buffer, unlike earlier applications. The court found the allegations insufficient. Although Amgen pointed to its own buffer-free product, prior rulings concerning buffer requirements, and testimony about a related patent, those facts might show Regeneron’s motivation to pursue claims without a buffer but did not support a reasonable inference that the ’099 patent’s inventorship declaration was false or that any specific individual knowingly deceived the PTO.

Second, during prosecution, Amgen challenged Regeneron’s statement that a preliminary amendment added no new matter. The court held that this allegation also failed. Relying on district court authority, it reasoned that a statement that an amendment contains “no new matter” is essentially a legal conclusion and is not material by itself where the examiner had the relevant prosecution materials available to make an independent determination. Because Amgen did not provide additional factual support showing materiality or knowing falsity, the court could not reasonably infer inequitable conduct.

Antitrust. Because the court had already found Amgen’s fraud allegations concerning the ’099 patent insufficient, it dismissed the antitrust claims based on that patent. Amgen alleged that Regeneron violated antitrust law by asserting patents that were fraudulently procured, including the ’099 patent and 12 earlier patents that Regeneron had previously asserted against Amgen but later dropped. The court explained that these Walker Process-type antitrust claims, based on alleged fraud, must satisfy Rule 9(b)’s heightened pleading standard.

The court reached a different result for the antitrust allegations tied to the earlier 2024 litigation patents. Regeneron argued that Amgen was barred from asserting those claims because they were compulsory counterclaims that should have been raised in the earlier 2024 action. The court agreed that the claims were compulsory and declined to apply the older exception in Mercoid Corp. v. Mid-Continent Inv. Co., 320 U.S. 661 (1944), broadly. However, because the earlier action had not yet reached final judgment, the court held that dismissal with prejudice was not appropriate. Instead, it dismissed those antitrust claims without prejudice, leaving open the question of whether Amgen could seek leave to assert them in the earlier action.

The court rejected Regeneron’s separate argument that Amgen could not claim litigation expenses as antitrust injury because Amgen participated in the statutory biosimilar patent-selection process. The court reasoned that Regeneron had threatened to assert, and ultimately did assert, the patents, and Amgen could not have avoided the alleged injury simply by trying to exclude them from the first wave of litigation.

Finally, the court dismissed Amgen’s California Unfair Competition Law (UCL) counterclaim because it was based on the same alleged conduct as the Sherman Act counterclaims. The UCL claim was dismissed with prejudice as to the ’099 patent and without prejudice as to the 2024 litigation patents.

Laches. The court denied Regeneron’s motion as to Amgen’s prosecution-laches defense and counterclaim. Amgen alleged that Regeneron unreasonably delayed pursuing the ’099 patent for more than 18 years after the parent provisional application was filed, and that the delay prejudiced Amgen because it had invested in developing a buffer-free aflibercept biosimilar formulation.

Regeneron argued that prosecution laches should not apply because the ’099 patent was filed under the post-GATT patent-term regime, where a patent’s term generally runs from the application date rather than the issuance date. According to Regeneron, the doctrine was developed to address strategic delays under the older system, where delaying issuance could extend the effective patent term.

The court rejected that argument at the pleading stage. It found that Regeneron’s authority did not establish a categorical rule barring prosecution-laches defenses for post-GATT patents, and it cited several district court decisions allowing the doctrine to apply to such patents.

Patent misuse. The court struck and dismissed Amgen’s patent-misuse defense and counterclaim with prejudice. Amgen alleged that Regeneron misused the ’099 patent by amending its claims to remove a buffer requirement and then enforcing the patent despite knowing it was invalid, unenforceable, and not infringed. The court explained that patent misuse generally concerns a patentee’s use of patent rights to gain an unfair commercial advantage or impermissibly broaden the patent’s scope with anticompetitive effect.

The court rejected Amgen’s theory that Regeneron misused the patent by amending the claims during prosecution. It reasoned that impermissible broadening cannot occur before a patent is granted, and Amgen cited no case finding patent misuse based merely on claim amendments during prosecution. The court also rejected Amgen’s fraudulent-procurement theory because, as discussed earlier, Amgen had not pleaded fraud with the particularity required by Rule 9(b).

The court also addressed whether Amgen could base patent misuse on Regeneron’s alleged bad-faith enforcement of the ’099 patent. It recognized that courts have disagreed over whether bad-faith litigation, standing alone and without adequately pleaded fraudulent procurement, can support a patent-misuse defense. After reviewing the competing Federal Circuit decisions, the court found C.R. Bard, Inc. v. M3 Sys., Inc., 157 F.3d 1340, 1372 (Fed. Cir. 1998), more applicable than Glaverbel Societe Anonyme v. Northlake Mktg. & Supply, Inc., 45 F.3d 1550 (Fed. Cir. 1995). In C.R. Bard, the Federal Circuit stated that it is not patent misuse to bring suit to enforce patent rights that were not fraudulently obtained. The court also relied on 35 U.S.C. § 271(d)(3), which provides that a patent owner is not deemed guilty of misuse merely for seeking to enforce its patent rights. It noted that the statute contains no express exception for suits allegedly brought in bad faith. Because Amgen had not adequately pleaded fraudulent procurement, the court concluded that its bad-faith-litigation theory could not sustain a patent-misuse defense or counterclaim.

Unclean hands. Relying on decisions that have struck similarly conclusory unclean-hands defenses, the court granted Regeneron’s motion and struck Amgen’s fourth additional defense with prejudice. Amgen pleaded only that Regeneron’s patent-infringement claim was barred “in whole or in part” by waiver, estoppel, and/or unclean hands. The court found that this bare allegation was “threadbare” and did not give sufficient notice of the factual basis for the defense.

The Case is No. 1:24-md-03103-TSK-JPM.

Judge: Kleeh, T.

Attorneys: Adam Pan (Williams & Connolly LLP) for Regeneron Pharmaceuticals, Inc. Jesse M. Weiss (Cravath, Swaine & Moore LLP) for Amgen, Inc.

Companies: Regeneron Pharmaceuticals, Inc.; Amgen, Inc.

Cases: Antitrust WestVirginiaNews GCNNews