The Federal Circuit’s decision last fall in Merck Serono S.A. v. Hopewell Pharma Ventures, Inc., Appeals 2025‑1210, ‑1211 (Fed. Cir. Oct. 30, 2025), reh’g and reh’g en banc denied (Jan. 22, 2026) (link), offers important guidance on the meaning of disclosures “by another” under pre-AIA 35 U.S.C. §§ 102(a) and (e)—a word-pairing that often determines whether a reference qualifies as prior art during prosecution and in litigation (including in inter partes review (IPR) proceedings).* The court’s opinion not only affirmed the Patent Trial and Appeal Board’s conclusion of obviousness in these IPRs but also clarified the legal standard for inventive entity identity, drawing heavily on the CCPA’s decision in In re Land, 368 F.2d 866 (CCPA 1966).
Key to the Federal Circuit’s decision is its explanation that a reference is “by another” unless the portions relied upon reflect the collective work of the same inventive entity named on the challenged patent. Merck, Slip Op. at 21. Continuing, the court said that “[a]ny incongruity in the inventive entity between the inventors of a prior reference and the inventors of a patent claim renders the prior disclosure ‘by another,’ regardless of whether inventors are subtracted from or added to the patent.” Id. at 21–22. This means that partial overlap—such as one inventor common to both the reference and the patent—is not enough to disqualify the reference from applying as prior art to the patent. Oddly enough, here, there was no overlap. The reference publication was authored by two individuals that are not among the inventors on either patent.
The court’s reasoning is grounded in the 1966 decision in Land, which was authored by Judge Rich, a principal author of the 1952 Patent Act. Land asks who invented the subject matter disclosed—not just who is named (as an author or inventor). Land concluded that a disclosure is prior art if it evidences knowledge “by another” (i.e., a different inventive entity) before the applicant’s invention date. Land also recognized that “A is not ‘another’ as to A, B is not ‘another’ as to B, or even that A & B are not ‘another’ as to A & B.” Land, 368 F.2d at 877. But when the inventive entities differ, the reference is prior art.
The Federal Circuit’s reasoning in Merck appears to be consistent with Land: when claims are the product of joint inventors, an earlier disclosure can be excluded from consideration as prior art (under pre-AIA § 102) only if the relied-upon portion is shown to be the joint inventors’ collective work. The reasoning is also consistent with its predecessor court’s post-Land decision in In re Katz, 687 F.2d 450, 455 (CCPA 1982), which concluded as sufficient (to disqualify § 102 prior art) a declaration by the sole applicant for a patent stating he was alone responsible for relied-upon disclosure in an earlier publication he co-authored with others who were graduate students working under his supervision. The Katz court concluded that given the sworn statement during prosecution, the co-authors need not supply confirming declarations. Id. at 456. Read together, Land and Katz mean that a patentee can avoid §§ 102(a) and (e) publication “by another” only by showing that the specific disclosure relied upon in the publication reflects the contributions of the same inventive entity as the challenged claims; if any part of the relied upon disclosure is attributable to someone outside that inventive entity, it remains “by another.” Merck failed to make this showing and, accordingly, its patents were canceled.
While the Merck court’s reasoning is anchored to Land, it also addresses and distinguishes the oft-cited decision in Applied Materials, Inc. v. Gemini Research Corp., 835 F.2d 279 (Fed. Cir. 1987)—a case that has sometimes been read to relax the identity-of-inventive-entity requirement. There, the court considered whether one patent naming two inventors is prior art to a later, family-related patent naming the same two inventors plus another. Id. at 281. The court explained that if the invention claimed in the later patent was fully disclosed in the earlier patent—and both originate from the same priority application—then the earlier disclosure could not be “by another.” Id. In Merck, the court explained that Applied Materials does not stand for the proposition that partial overlap of inventors is sufficient to defeat prior art status. Instead, it illustrates a narrow exception in situations where the reference and the patent descend from the same priority application, reflecting a continuous chain of development from the same inventive entity’s work. Outside that situation, the Land rule—requiring complete identity—applies. Merck, Slip Op. at 16–17.
The court further discussed several later decisions, including Google LLC v. IPA Techs. Inc., 34 F.4th 1081 (Fed. Cir. 2022) (discussed here), characterizing this collection as “consistently require[ing] identity of inventive entity to exclude a reference from the prior art as not ‘by another.’” Merck, Slip Op. at 18–22. The court said that Land forecloses Merck’s argument that it’s bad policy to deny a patent simply because an additional inventor collaborated with co-inventors who previously authored a reference disclosure. Id. at 22–23. While there may be merit to Merck’s policy critique, here there was no overlap: Merck’s patents name four individuals as inventors and none is a co-author of the reference publication (applied as prior art).
Dissatisfied with the court’s interpretation of Land, Applied Materials, and these other decisions, Merck petitioned the court to rehear the appeals. Among other things, Merck argues that Land should be overruled or, as other courts have done, limited its import under allegedly analogous facts. See General Motors Corp. v. Toyota Motor Co., 667 F.2d 504 (6th Cir. 1981) (addressing the pre-AIA 35 U.S.C. § 102(f) derivation provision); see also, Shields v. Halliburton Co., 667 F.2d 1232 (5th Cir. 1982) (same). Hopewell Pharma opposed, arguing, among other things, that Land prevents a patent applicant from adding (as his/her co-inventors) collaborators to avoid the collaborators’ prior art. Recently, the court denied Merck’s petitions in this case and also in the parallel case.*
Land framed the important fact question of who invented relevant portions of the reference. Setting aside the complexities in assessing inventorship, in Merck’s wake, the Patent Office and district courts may continue to struggle with assessing inventorship and how much and what kind of corroboration—under the amorphous “rule of reason”—is sufficient to prove that individuals named as inventors on the patent (or application) were solely responsible for an earlier disclosure present in a reference that includes additional authors. Further, Merck’s exposition of Applied Materials may invite disputes about the prior art status of patent family members involving continuation-in-part patents and mixed inventorship histories. Patent applicants and owners should prepare to prove complete identity of inventive entity—or provide robust evidence of corroborated inventorship—when seeking to exclude references in prosecution, inter partes reviews, and in litigation.
Long after authoring the Land decision, Judge Rich commented that “[t]he life a patent solicitor has always been a hard one.”** Merck has made that life no easier.
* In a parallel case decided the same day, the court affirmed the Board’s cancelation of related Merck patents on the same issue. Merck Serono S.A. v. TWI Pharms., Inc., Appeals 2025-1463, -1464 (Fed. Cir. Oct. 30, 2025) (non-precedential), reh’g denied (Jan. 22, 2026) (link).
** Giles S. Rich, The Extent of the Protection and Interpretation of Claims-American Perspectives, 21 Int’l Rev. Indus. Prop. & Copyright L., 497, 499 (1990).