Federal Circuit Reaffirms Pre-AIA Law in Patent Dispute

Patent law has a special talent for making yesterday’s rules ruin today’s lunch. Just when everyone got comfortable talking about the America Invents Act, the U.S. Court of Appeals for the Federal Circuit stepped in and reminded the patent world that pre-AIA law is not dead, not retired, and definitely not relaxing on a beach somewhere. In Merck Serono S.A. v. Hopewell Pharma Ventures, Inc., the court reaffirmed a strict rule for determining when an earlier disclosure counts as prior art “by another” under the old patent statute. The result was a sharp loss for Merck, a useful win for patent challengers, and a loud warning to companies still relying on legacy patent portfolios.

The case centered on Merck’s patents covering oral cladribine dosing regimens for treating multiple sclerosis. Hopewell challenged those patents in inter partes review, arguing that earlier references made the claimed methods obvious. Merck fought back by saying one key reference should not count as prior art because the work was not really “by another.” The Federal Circuit disagreed and, in doing so, clarified an old but still powerful principle: under pre-AIA law, overlapping inventors are not enough. To avoid prior-art status, the relied-on disclosure must reflect the same inventive entity as the challenged patent. In plain English, close does not count.

For patent lawyers, this decision is a doctrinal cleanup job. For innovative companies, it is a reminder to document inventorship like your future depends on it, because sometimes it does. For everyone else, it is proof that patent disputes can turn on a few names, a few dates, and a few lines in an old application that suddenly become the star of the show.

What Happened in the Merck v. Hopewell Patent Dispute?

The dispute involved two Merck patents directed to methods of treating multiple sclerosis using oral cladribine in a staged regimen. The claimed approach included an induction period, a cladribine-free break, a maintenance period, and another no-treatment interval. That sort of treatment schedule may sound like a medical calendar with attitude, but in patent law it becomes claim language, and claim language becomes battlefield terrain.

Hopewell challenged the patents before the Patent Trial and Appeal Board, relying primarily on two references. The first was an international patent publication often referred to as Bodor, which described oral cladribine formulations and included a dosing schedule involving treatment in the first month, treatment in the second month, and then ten months without treatment. The second was a 1998 clinical paper by Stelmasiak discussing cladribine treatment in patients with relapsing-remitting multiple sclerosis.

Merck’s priority applications were filed in late December 2004. The Bodor application had been filed earlier in March 2004 and published in October 2004. That timing mattered a lot. If Bodor qualified as prior art, Merck had a serious problem. If Bodor could be disqualified as not being “by another,” Merck had a fighting chance.

The PTAB sided with Hopewell. It held that the challenged claims were unpatentable as obvious over Bodor and Stelmasiak. On appeal, the Federal Circuit affirmed. It also used the case to clarify how pre-AIA Sections 102(a) and 102(e) should work when inventorship overlaps, or appears to overlap, between the earlier reference and the later patent.

Why Pre-AIA Patent Law Still Matters

The America Invents Act changed U.S. patent law in major ways, most notably by moving the system to a first-inventor-to-file framework. But the switch did not erase older applications. If an application falls under the pre-AIA regime, old rules still govern novelty, prior art, and related validity fights. That means legacy patents can still generate very modern headaches.

That is exactly why Merck v. Hopewell matters. The patents at issue traced back to filings before the AIA transition date, so the court had to apply the older statutory language. And under that older law, phrases like “by another” and “by others” still carry serious force. They sound small. They are not small. They are tiny legal levers that can move million-dollar patent rights.

The Federal Circuit’s 2025 decision in In re Riggs reinforced the same broader reality. In that case, the court addressed another pre-AIA Section 102(e) issue and made clear that an earlier provisional filing date only helps a prior-art reference to the extent the relied-on subject matter is actually supported. Different facts, same theme: pre-AIA doctrine is still alive, still technical, and still very capable of surprising anyone who treats it like dusty museum law.

The Core Holding: “By Another” Means the Same Inventive Entity, Not Something Sort Of Similar

The central legal issue in Merck v. Hopewell was whether the Bodor disclosure could be excluded from prior art because it allegedly reflected work by at least one of the inventors later named on Merck’s patents. Merck argued that a disclosure created by fewer than all of the later joint inventors should not automatically count as prior art “by another.” That argument had some strategic appeal. If accepted, it would have made it easier for patent owners to neutralize earlier references arising out of overlapping collaborative work.

The Federal Circuit rejected that theory. It relied heavily on older precedent, especially In re Land, and clarified that a reference is excluded from prior art only when the relied-on disclosure reflects the work of the same inventive entity as the challenged patent. Not a similar team. Not a partial overlap. Not “well, they were all in the same orbit.” The same inventive entity.

That matters even more in joint-inventor situations. The court explained that if a patent lists joint inventors, then the earlier disclosure must reflect the collective work of that same joint inventive entity to avoid being treated as prior art. A disclosure by a subset of inventors does not automatically qualify as the inventors’ “own work” for this purpose. That is the doctrinal punchline, and it lands hard.

This part of the ruling is especially important because collaborative research is messy in real life. Projects evolve. Teams change. Researchers contribute at different times. Drafts circulate. Applications get filed by one business partner before the other side has finished its paperwork. Patent law, however, likes crisp lines. The Federal Circuit drew one here: unless the relied-on disclosure embodies the same inventive entity, it can still be prior art.

Why Merck Lost the Inventorship Fight

Merck’s argument was not just legal; it was factual. The company tried to show that one of its named inventors, Dr. De Luca, had contributed to the specific dosing disclosure in Bodor. If Merck had proven that the relevant portion of Bodor reflected the joint work of the same inventive entity behind the Merck patents, Bodor might have been disqualified as prior art.

But the evidence fell short. The Federal Circuit agreed with the PTAB that Merck failed to provide sufficiently credible, corroborated evidence that De Luca made an inventive contribution to the specific six-line dosing regimen in Bodor. That detail matters. Patent law does not reward vague participation trophies. Being part of a project team is not the same as contributing to the claimed inventive subject matter. When the legal question turns on inventorship, courts want proof tied to the exact disclosure being relied upon.

Merck also argued that the PTAB had effectively shifted the burden of persuasion. The Federal Circuit rejected that too. It held that the ultimate burden remained with the petitioner, but once Hopewell made its initial showing that Bodor qualified as prior art, Merck had the burden of coming forward with evidence to support its effort to disqualify the reference. In other words, Hopewell lit the fuse, and Merck still needed better fireproofing.

Obviousness Still Did the Heavy Lifting

Although the “by another” issue grabbed the doctrinal spotlight, the case also remained an obviousness dispute from start to finish. Once Bodor stayed in the prior-art pool, the combination with Stelmasiak became difficult for Merck to overcome. The Board found that Bodor taught the induction phase and the long drug-free interval, while Stelmasiak supplied teachings supporting retreatment and repeated courses over time. The Federal Circuit found substantial evidence for that conclusion.

The court also upheld the Board’s reasoning on motivation to combine and reasonable expectation of success. That is important because patent owners sometimes win even after losing an individual prior-art skirmish if they can show the combination analysis is too speculative. Merck did not get that break here. The Federal Circuit concluded that the record sufficiently supported the Board’s view that a skilled artisan would have had reason to combine the references and would have expected the regimen to work.

So while the case is being remembered for its pre-AIA inventorship analysis, the practical result came from a familiar patent-law one-two punch: first, the key reference stayed alive; second, the obviousness theory held together.

Why This Decision Matters for Patent Owners and Challengers

1. Legacy patents can still trigger old-law traps

Any company with patents tied to pre-March 16, 2013 filings should pay attention. The Federal Circuit is still willing to apply pre-AIA doctrine carefully and strictly. If your portfolio includes older applications, the old novelty and prior-art rules remain very much in play.

2. Collaboration without documentation is asking for trouble

This decision is a cautionary tale for joint development projects, especially in pharmaceuticals and biotech where collaboration is common and timelines are long. If multiple organizations are working together, it is not enough to assume everyone will later agree on who invented what. That assumption ages about as well as milk in a server room.

3. Inventorship evidence must be specific

General testimony that someone was involved in the project will not do the job. The evidence has to tie a particular inventor to the particular disclosure that matters. If the dispute is about six lines in an earlier reference, then the proof had better talk about those six lines and not just the overall vibe of collaboration.

4. PTAB challengers got a useful precedent

For petitioners in IPRs and defendants in patent litigation, the decision offers a clearer path for arguing that earlier disclosures remain prior art despite overlapping or allegedly related inventors. That does not make the issue automatic, but it does make the patent owner’s rebuttal burden more concrete and more demanding.

Would the Result Be Different Under the AIA?

Possibly, and that is one reason the case is so interesting. The AIA changed the statutory framework and created different exceptions tied to disclosures obtained from the inventor, common ownership, and certain joint research agreements. Modern patent law is still no picnic, but it is at least a different picnic basket.

Under current Section 102, the language and exceptions no longer map perfectly onto the pre-AIA “by another” framework. In some modern collaborations, common ownership or a qualifying joint research agreement may provide stronger protection against internal or quasi-internal prior art. That said, none of that rescued Merck here because this case lived in the pre-AIA world. The court was not deciding what should happen under today’s statute. It was deciding what the older statute still requires.

That distinction matters for strategy. Companies should not assume that modern collaboration rules can be retrofitted onto old patents. They should also not assume that because the AIA changed the law, old interpretive fights are gone. They are not. They just show up wearing older section numbers.

Practical Experiences and Real-World Lessons from Pre-AIA Patent Disputes

One of the clearest real-world lessons from disputes like Merck v. Hopewell is that inventorship problems usually begin long before the lawsuit. They begin in project meetings, email chains, draft presentations, and half-finished invention disclosures. A research team may know that several scientists were involved in a broader program, but that does not answer the narrower legal question of who contributed to a specific claim limitation or a specific dosing schedule. Years later, when the patent is challenged, that missing detail becomes painfully expensive.

Another common experience is that collaboration agreements often look thorough until litigation starts. Teams may negotiate licensing terms, manufacturing roles, milestone payments, and publication rights, yet leave inventorship tracking oddly informal. That is fine right up until it is not. In legacy patent fights, parties often discover that the real vulnerability is not the science but the recordkeeping. The lab work may have been brilliant; the paper trail may have been allergic to specifics.

Patent owners also learn, sometimes the hard way, that broad project participation is not a substitute for corroborated inventive contribution. Scientists may have attended strategy sessions, reviewed drafts, or supervised programs, but courts want evidence that connects an inventor to the actual subject matter used in the prior-art or validity analysis. That means contemporaneous notes, clear attribution, document version history, and witness testimony that does more than shrug politely at a deposition transcript.

For challengers, the experience is almost the mirror image. These cases show that old references can become powerful again when a patent owner cannot prove the inventive entity matches up. A reference that initially looks messy because of collaboration history may still qualify as prior art if the patent owner cannot establish that the relied-on disclosure was really the same team’s joint work. That makes deep factual development worthwhile. Sometimes the winning move in a patent challenge is not a flashy doctrine. It is a boring file review done exceptionally well.

There is also a broader business lesson here. Companies managing pre-AIA portfolios should audit them with the same seriousness they bring to current filings. Old patents may involve old agreements, former employees, reorganized subsidiaries, or acquired assets with incomplete prosecution histories. Those details can become front-page issues in an IPR or district court fight. Legacy patents are not just historical artifacts; they are live assets with live risks.

And finally, there is the lesson every in-house patent team eventually learns: never assume a case is “just about the old law.” The old law is still law. It can still invalidate claims, reshape litigation strategy, affect deal value, and influence how future collaborations are documented. In that sense, Merck v. Hopewell is not just a backward-looking pre-AIA case. It is a current warning label for anyone building patents through teamwork, especially when the teamwork spans multiple entities and multiple years.

Conclusion

The Federal Circuit’s decision in Merck Serono v. Hopewell Pharma Ventures is a crisp reminder that pre-AIA patent law still has teeth. The court reaffirmed that under the old statute, an earlier disclosure is not excluded from prior art just because it sits near the same research program or shares some inventive DNA. To avoid being treated as prior art “by another,” the relied-on disclosure must reflect the same inventive entity as the challenged patent. Merck could not make that showing, so Bodor stayed in the case, and the obviousness challenge succeeded.

For patent owners, the lesson is straightforward: document inventorship carefully, especially in collaborative development. For challengers, the decision supplies a cleaner framework for testing whether older references can still do real invalidity work. And for everyone operating with legacy patents, this ruling says the quiet part out loud: pre-AIA law is still very much in the building, and it still knows how to win arguments.

Note: This article is for general informational purposes only and is not legal advice.

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