GlaxoSmithKline v. Pfizer/BioNTech and Moderna — Delaware Court Keeps Prosecution Laches Defense Alive in mRNA Vaccine Patent War

Background

GlaxoSmithKline filed three coordinated patent infringement actions in the District of Delaware against the developers and manufacturers of the two most successful COVID-19 mRNA vaccines. The suits assert 15 patents across three cases: eight patents against Pfizer and BioNTech SE (the Comirnaty/Paxlovid COVID vaccine companies) in case 24-512, and seven patents each against Moderna in cases 24-1135 and 24-1136. All patents cover fundamental mRNA formulation and lipid nanoparticle (LNP) delivery technology — the core mechanism by which mRNA vaccines deliver genetic instructions into human cells.

The timing of the suits attracted immediate attention in the patent bar. Pfizer/BioNTech and Moderna (collectively PBNT and Moderna) contended that GSK engaged in prosecution laches — a doctrine that strips a patent holder of the right to enforce its patents when it unreasonably delayed prosecution and prejudiced parties who relied on the belief that the claimed technology was in the public domain. According to the defendants, GSK filed or continued prosecution of seven of the eight PBNT-suit patents on or after April 1, 2020 — just two weeks after Pfizer/BioNTech publicly announced their COVID mRNA vaccine collaboration. GSK, the defendants alleged, held claims pending for 9 to 12 or more years across continuation applications, then broadened their scope once competitors’ technology became visible. PBNT and Moderna each asserted prosecution laches both as an affirmative defense and as a counterclaim. Moderna also asserted obviousness-type double patenting (OTDP) on the ground that GSK’s overlapping continuation claims should not give it effectively extended patent protection.

GSK moved to dismiss the laches counterclaims and strike the laches affirmative defenses in all three cases, and also to strike Moderna’s OTDP counterclaim and defense. This 22-page Memorandum Order resolves all three motions.

The Court’s Holding

Judge Williams denied GSK’s motions on prosecution laches across all three cases, and granted the motion on OTDP against Moderna.

Prosecution laches (all three cases): The court first held that prosecution laches applies to post-GATT patents, rejecting GSK’s argument that the doctrine should be limited to pre-GATT (pre-1995) cases. The court followed the Federal Circuit’s decision in Personalized Media Communications v. Apple, 57 F.4th 1346 (Fed. Cir. 2023), and Hyatt v. Hirshfeld, 998 F.3d 1347 (Fed. Cir. 2021), which extended prosecution laches to the modern continuation practice environment. The court also held that the six-year prejudice presumption from Hyatt does not apply when prosecution laches is raised as a defense to infringement—it applies only in § 145 civil actions against the USPTO.

On the adequacy of the pleadings, Judge Williams found PBNT and Moderna had plausibly alleged both prongs of prosecution laches: (1) unreasonable and inexcusable delay in prosecution, based on the allegation that GSK filed or continued seven of the eight PBNT patents on or after April 1, 2020, immediately after competitors’ vaccine technology was publicized; and (2) prejudice, based on the allegation that PBNT and Moderna invested billions of dollars developing mRNA vaccine technology during the period the continuation claims were pending, only to face patent infringement suits after the technology succeeded commercially. The court observed that filing or continuing patent applications to track a competitor’s publicly announced technology “is the precise concern that animates prosecution laches.”

Obviousness-type double patenting (Moderna cases only): The court granted GSK’s motion to dismiss and strike Moderna’s OTDP counterclaim and defense. OTDP exists to prevent patent holders from extending their effective monopoly by obtaining continuation patents with overlapping claims. But because all of GSK’s asserted patents share the same expiration date (July 6, 2031) via terminal disclaimers, there is no term extension for OTDP to address. And because GSK retains common ownership over all the patents, there is no risk of harassment by serial litigation by different assignees. Both rationales for OTDP are therefore absent, and the defense fails as a matter of law at this stage.

Key Takeaways

• Prosecution laches is alive and well in the post-GATT era. Defendants can raise this doctrine against any patent, not just pre-1995 continuations. Patent owners who maintain continuation applications for many years, especially while competitors develop similar technology, face real exposure to a prosecution laches defense at trial.
• Strategic claim-timing is risky. The allegation that GSK filed most of its continuation applications within weeks of its rivals’ public vaccine announcement illustrates the litigation danger of using continuation practice to tailor claim scope to a competitor’s public disclosures. Courts will let juries hear that story.
• The Hyatt presumption is narrower than some thought. The six-year prejudice presumption applies in PTO civil actions, not in defensive use of prosecution laches in infringement suits. Patent owners cannot benefit from the presumption, and defendants must plead facts showing actual prejudice.
• OTDP fails when terminal disclaimers level the expiration dates. If a patent owner uses terminal disclaimers to harmonize expiration dates across a family of continuation patents, OTDP is unavailable to defendants as a defense—the doctrine has no work to do.

Why It Matters

The mRNA vaccine patent wars are among the highest-stakes IP disputes of the decade. Billions of dollars in COVID vaccine revenue hang in the balance, and the outcome of these cases will shape the royalty economics of a technology platform that pharmaceutical companies are rapidly deploying for influenza, cancer, and other vaccines. The prosecution laches doctrine—long considered a fringe defense rarely succeeding at trial—is now squarely in play in some of the most consequential patent cases in memory. The allegation of “submarine patenting” (drafting continuation claims to cover a competitor’s revealed technology) is a compelling narrative that resonates beyond the courtroom.

For patent practitioners, the ruling signals that courts will look skeptically at continuation applications filed immediately after a competitor’s public technology disclosure, especially when the prior prosecution history shows extended delay. The decision is also a clean reminder that terminal disclaimers cure OTDP problems but do not shield against prosecution laches—the two doctrines target different abuses. Fact discovery closes July 29, 2026; whether prosecution laches can be proven at trial is a question for another day.