The US Court of Appeals for the Federal Circuit affirmed the Patent Trial & Appeal Board’s decision finding claims directed to cladribine regimens for treating multiple sclerosis unpatentable as obvious. The Court clarified that a disclosure can only be excluded as prior art under pre-AIA § 102(e) if it reflects the collective work of the same inventive entity as the challenged patent. Merck Serono S.A. v. Hopewell Pharma Ventures, Inc., Case No. 25-1210 (Fed. Cir. Oct. 30, 2025) (Hughes, Linn, Cunningham, JJ.)

Merck holds patents covering methods for treating multiple sclerosis using specific oral cladribine dosing regimens. Hopewell Pharma filed inter partes review (IPR) petitions challenging these patents, asserting that the claims were obvious in light of two prior art references disclosing similar cladribine dosing schedules.

Merck argued that one reference, Bodor, was not prior art because one of the named inventors on the challenged patents, De Luca, allegedly contributed to the six-line dosing disclosure in Bodor. The Board rejected this argument, finding that Merck failed to provide corroborated evidence of De Luca’s inventive contribution and concluding that the Bodor disclosure was “by another.” The Board ultimately found all claims unpatentable as obvious over the two prior art references. Merck appealed.

On appeal, Merck contended that the Board erred by applying a “bright-line rule” requiring complete identity of inventive entities to exclude a reference as not “by another.” The Federal Circuit disagreed, reaffirming the long-standing principle from In re Land (CCPA 1966): Any difference in inventive entity, whether by adding or omitting inventors, renders the prior disclosure “by another” under pre-AIA § 102(e).

The Federal Circuit explained that when a patent results from collaboration among joint inventors, a reference can be excluded only if the relied-upon portions of the reference represent the collective efforts of the same inventive team named as inventors in the patent. While evidence from fewer than all inventors may suffice, it must demonstrate that the disclosure embodies their joint contribution. Thus, even partial overlap of inventors does not prevent the earlier disclosure from being prior art.

Merck also argued that the Board’s interpretation conflicted with language in the Manual of Patent Examining Procedure (MPEP), which suggests that the work of “at least one joint inventor” could avoid prior art treatment. The Federal Circuit rejected this claim, noting that the MPEP cites Land and defines “by another” as “a different inventive entity.” Because this rule has been long established, the Court concluded that Merck had sufficient notice and was not deprived of a fair opportunity to respond.

Finally, Merck asserted that the Board failed to apply the “rule of reason” when assessing whether De Luca contributed to Bodor. The Federal Circuit disagreed, finding that the Board properly considered all evidence, including declarations, meeting minutes, and testimony, and reasonably concluded that De Luca’s alleged role was not corroborated or significant enough to make him a co-inventor.

Practice note: This decision reinforces that under the pre-AIA statute, the phrase “by another” requires complete identity of the inventive entity to [...]

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