Patents

Expiration, Not Issuance: Gilead v. Natco Rewrites Obviousness-Type Double Patenting

The Federal Circuit held that a later-issued, earlier-expiring patent can serve as a double-patenting reference, anchoring the doctrine to expiration dates in the post-URAA world.

June 17, 2025
Generic antiviral capsules beside a calendar marking patent expiration dates
Gilead's two antiviral patents issued a year apart but expired nearly two years apart—forcing the court to decide which date controls double patenting. Shutterstock
Educational content, not legal advice. This article explains general legal concepts. It does not create an attorney–client relationship. For your specific situation, consult a licensed attorney.

In Gilead Sciences, Inc. v. Natco Pharma Ltd., No. 2013-1418 (Fed. Cir. Apr. 22, 2014), the U.S. Court of Appeals for the Federal Circuit confronted a deceptively narrow question with sweeping portfolio consequences: when two commonly owned patents claim obvious variations of the same invention, does it matter which one issued first, or only which one expires first? Writing for the panel, Judge Chen held that expiration—not issuance—controls. A patent that issued later but expires earlier can still serve as an obviousness-type double patenting (ODP) reference against a patent that issued earlier but expires later. Chief Judge Rader dissented. The decision reversed a contrary ruling from the U.S. District Court for the District of New Jersey and reoriented double-patenting analysis around the realities of patent term in the post-URAA era.

At a glance

  • Patents: U.S. Patent No. 5,763,483 (the ‘483 patent) and U.S. Patent No. 5,952,375 (the ‘375 patent), both directed to antiviral compounds and sharing the same inventors and similar written descriptions—but not claiming priority to a common application.
  • The timing wrinkle: The ‘483 patent issued first (June 1998) but expires later (December 27, 2016). The ‘375 patent issued second (1999) but expires earlier—roughly 22 months before the ‘483 patent.
  • The dispute: In ANDA litigation, Natco argued the ‘483 patent was invalid for obviousness-type double patenting over the earlier-expiring ‘375 patent. Gilead countered that the ‘375 patent could not be a reference because it issued after the ‘483 patent.
  • District court: Agreed with Gilead; held that a later-issued patent cannot serve as an ODP reference.
  • Holding: Reversed. An earlier-expiring patent can be an ODP reference for a later-expiring patent regardless of issuance order; the relevant comparison is expiration dates.

The doctrine and why timing suddenly mattered

Obviousness-type double patenting is a judge-made doctrine that prevents an inventor from extending the effective term of patent protection by obtaining a second patent on an obvious variation of an already-patented invention. Its animating principle, the court stressed, is a “bedrock” bargain: when a patent expires, the public gains the right to practice the invention and its obvious modifications. A second, later-expiring patent covering those obvious modifications would re-fence ground the public was promised.

For most of the doctrine’s history, issuance order and expiration order marched together. Pre-1995 patent terms ran 17 years from the issue date, so the first patent to issue was almost always the first to expire. The Uruguay Round Agreements Act (URAA) severed that link by changing the term to 20 years from the earliest filing date. Now two related patents can issue in one sequence and expire in the opposite sequence—precisely the inversion at the heart of Gilead. The ‘483 patent issued first but, because of its later priority date, sits on a longer leash.

Why expiration controls

Gilead’s position had surface appeal: the Federal Circuit’s older cases sometimes spoke of double patenting in terms of which patent issued first, treating the first-issued patent as the “reference.” But Judge Chen’s opinion reasoned that those formulations were artifacts of the pre-URAA regime, where issue date was a faithful proxy for expiration. Once Congress decoupled term from issuance, clinging to issue date would let patentees manipulate the doctrine.

Consider the manipulation the court feared. If issuance order governed, an applicant could file two applications with different priority dates, steer the longer-term application to issue first, and thereby immunize it from ODP attack by the shorter-term patent that issues later. The public would lose nearly two years of free access to obvious variants—exactly the unjustified term extension ODP exists to prevent. By anchoring the inquiry to expiration, the court closed that loophole: the later-expiring patent is always the one tested against the earlier-expiring patent, because the later-expiring patent is the one that threatens to extend the monopoly.

The court therefore held the ‘375 patent (earlier-expiring) a proper reference against the ‘483 patent (later-expiring), and remanded for the obviousness comparison of the claims.

Rader’s dissent and the structural critique

Chief Judge Rader dissented. His core objection was that the majority imported a remedy for a problem better solved by the terminal disclaimer mechanism and by examination, and that the relevant comparison should focus on patents sharing a common priority date. He warned that the majority’s expiration-based rule injected uncertainty into portfolios assembled in good faith, where applicants could not always control issuance sequence or foresee how priority chains would map onto expiration. The disagreement was not really about the anti-evergreening principle—both opinions embraced it—but about how far the courts should stretch a judge-made doctrine to police term, versus leaving that work to the patent term statutes and the disclaimer practice already built into prosecution.

Open questions

Gilead answered the issuance-versus-expiration question but left several frontiers. The most consequential concerns patent term adjustment (PTA): when a later-expiring patent’s extra life comes from PTA awarded for PTO delay—rather than from a different priority date—should ODP still strip that congressionally granted term? The Federal Circuit’s later cases wrestled with that interaction, and the answer is doctrinally distinct from Gilead’s priority-date scenario. A second open area is the role of the safe-harbor and terminal-disclaimer tools: Gilead identifies the reference, but whether a patentee can cure the problem with a disclaimer depends on common ownership and timing that vary case to case. Finally, Gilead involved patents that did not share a priority date; how its logic applies within a single, complex priority chain remains a recurring litigation question.

Implications

  • Map expiration dates, not just issue dates, across a family. Two patents on obvious variations create ODP exposure whenever the later-expiring one could extend the monopoly—even if it issued first.
  • Beware divergent priority chains. Related patents that do not share a common priority date can expire in the opposite order from issuance, the exact trap Gilead addresses.
  • Consider terminal disclaimers proactively. Where commonly owned patents claim obvious variants, a terminal disclaimer tying expiration dates together can defuse an ODP attack before litigation.
  • Pharma and ANDA portfolios face heightened scrutiny. Gilead arose in Hatch-Waxman litigation, where generic challengers actively hunt for term-extending second patents.
  • The remedy is unenforceability/invalidity of the later-expiring claims, a severe outcome that makes early portfolio auditing worthwhile.

Frequently asked questions

What exactly did Gilead change about double patenting? It held that the proper double-patenting reference is the earlier-expiring patent, not the earlier-issued patent. Before Gilead, courts often spoke in terms of issuance order, which made sense when term ran from the issue date. After the URAA tied term to filing date, Gilead realigned the doctrine with expiration.

Why does the difference between issuance and expiration matter so much? Because the URAA changed patent term to 20 years from the earliest filing date, two related patents can issue in one order and expire in the opposite order. If issuance order controlled, a patentee could route a longer-term patent to issue first and shield it from double-patenting attack—extending the monopoly on obvious variants, which is precisely what the doctrine forbids.

Can a patentee fix a Gilead-type problem? Often, yes—through a terminal disclaimer that ties the later-expiring patent’s expiration to the earlier-expiring patent’s, eliminating the unjustified term extension. The availability and timing of that cure depend on common ownership and the procedural posture, so portfolios are best audited before a challenge arises.

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