On June 16, 2026, U.S. District Judge Gregory B. Williams of the United States District Court for the District of Delaware issued a memorandum order resolving three partial motions to dismiss counterclaims and strike affirmative defenses in GlaxoSmithKline Biologicals SA’s and GlaxoSmithKline LLC’s (“GSK”) mRNA patent infringement litigation against Moderna, Inc. entities (“Moderna”) and Pfizer Inc., BioNTech entities (collectively “PBNT”).

Background

GSK filed separate suits against Moderna (Civil Action Nos. 24-1135 and 1136 each filed on October 12, 2024) and PBNT (Civil Action No. 24-512 filed on April 25, 2024) alleging infringement of multiple U.S. patents relating to mRNA and lipid nanoparticle (LNP) technology. The case schedules of the Moderna and PBNT cases were consolidated on March 18, 2025, for judicial economy.

The asserted patents are: U.S. Patent Nos. 11,324,770 (filed Jan 13, 2020); 11,690,861 (filed December 13, 2022); 11,690,864 (filed December 13, 2022); and 11,717,529 (filed December 13, 2022); each a continuation application claiming priority to Provisional Patent Application No. 61/361,789 filed on July 6, 2010, and 11,786,467 (filed December 22, 2021); and 11,883,534 each a continuation application claiming priority to Provisional App. No. 61/361,830 also filed on July 6, 2010 (collectively the “Asserted Patents”).

The accused products are (1) the Moderna Spikevax® and mRESVIA® mRNA vaccine products for COVID-19 and respiratory syncytial virus (RSV), respectively, and (2) the PBNT Comirnaty® products for COVID-19 (collectively “Accused Products”).

Moderna and PBNT each responded with counterclaims and affirmative defenses including for prosecution laches and GSK moved to dismiss those counterclaims under Rule 12(b)(6) and affirmative defenses under Rule 12(f).

Laches

Nearly all of the applications that led to issuance of the asserted patents were filed after features of the Accused Products were publicly known and about 10 years from the earliest provisional and original non-provisional filing dates.

While this is accepted practice when prosecuting patents before the United States Patent and Trademark Office (“USPTO”), the Federal Circuit has held that the doctrine of prosecution laches may render a patent unenforceable when the patentee causes unreasonable and unexplained delay in prosecution that constitutes an egregious misuse of the statutory patent system under the totality of the circumstances. Cancer Rsch. Tech Ltd. v. Barr Lab’ys Inc., 635 F.3d 724, 728 (Fed. Cir. 2010).

At the pleading stage, a defendant must allege: (1) that the patentee’s delay was unreasonable and inexcusable under the totality of the circumstances, and (2) that the accused infringer suffered prejudice attributable to the delay. Personalized Media Commc’ns, LLC v. Apple Inc., 57 F.4th 1346, 1354 (Fed. Cir. 2023). There are no bright-line rules; courts evaluate the totality of circumstances as a matter of equity.

Ruling

The Court found that both Moderna and PBNT sufficiently alleged unreasonable and inexcusable delay. Key factual allegations included: prosecution histories spanning nine to twelve years from the priority applications; multiple requests for continued examination; and — importantly — allegations that GSK began pursuing claims of broader scope directed at mRNA and LNP technology only after information about defendants’ COVID-19 vaccine compositions entered the public domain. The Court reasoned that, after accepting all pleaded facts as true, these allegations support the reasonable inference that GSK’s prolonged prosecution was used not merely to obtain allowance of the originally claimed invention, but to adjust claim scope in response to intervening competitor disclosures — which raises relevant concerns that prosecution laches is designed to address.

To establish prejudice, an accused infringer must allege intervening rights — i.e., that it or others invested in, worked on, or used the claimed technology during the period of delay, and that it would have acted differently had the patentee prosecuted in a timely manner. Cancer Rsch. Tech Ltd., 625 F.3d at 729-731. Both Moderna and PBNT alleged they invested substantial time and resources developing mRNA and LNP technologies during the period of GSK’s alleged delay, only to face claims of broader scope that were enlarged after those investments were made. The Court found these allegations sufficient at the pleading stage, distinguishing the Federal Circuit’s post-trial decision in Google LLC v. Sonos, Inc. (Sonos II), 2025 WL 2473258 (Fed. Cir. Aug. 28, 2025), which held that a defendant could not “be prejudiced by incorporating into its products a feature that was publicly disclosed” in the specification of a predecessor application of the asserted patents “prior to the defendant’s investment”, on the grounds that Sonos II was decided on a fully developed evidentiary record.

The Court also addressed the specific questions of (1) whether prosecution laches applies to post-General Agreement on Trade and Tariffs (“GATT”) patents and if so (2) whether the presumption for prosecution laches is applicable in this case.

GSK argued that prosecution laches does not apply to patents issued under the post-General

Agreement on Trade and Tariffs (“GATT”) patent term framework (i.e., patents with terms measured from the application filing date rather than the grant date), contending the doctrine developed specifically to address so-called “submarine patents” under the old system. The Court rejected this argument, relying on Mojo Mobility, Inc. v. Samsung Elecs. Co., 2024 WL 3354705 (E.D. Tex. June 11, 2024), and the Federal Circuit’s decision in Personalized Media Communications, which declined to limit prosecution laches to a specific fact pattern and instead focused on whether prosecution was conducted in an equitable manner.

The Federal Circuit held in Hyatt v. Hirshfeld, 998 F.3d 1347 (Fed. Cir. 2021), that in the context of a § 145 civil action against the USPTO, an unreasonable prosecution delay of six or more years raises a presumption of prejudice, including intervening rights. Both Moderna and PBNT sought to invoke this presumption. The Court declined to extend the presumption beyond the § 145 context, finding that Hyatt expressly limits it to that setting. Accordingly, the defendants were required to affirmatively plead prejudice without the benefit of any presumption.

Conclusions

The Court emphasized that prosecution laches is an inherently fact-intensive inquiry turning on the totality of the circumstances. The surviving prosecution laches counterclaims and affirmative defenses will proceed to discovery. Whether the evidence ultimately supports a finding of prosecution laches — and thus unenforceability of the asserted patents — remains to be determined at summary judgment or trial on a fully developed factual record.

How this laches issue plays out in in this case will be interesting to follow, especially for parties that seek to enforce and defend against such later-filed patent applications based on old portfolios that are still active.