Federal Circuit clarifies the term “by another” in pre-AIA 35 U.S.C. §§ 102(a) and (e)
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On October 30, 2025, in Merck Serono S.A. v. Hopewell Pharma Ventures, Inc., Nos. 2025-1210, 2025-1211, the US Court of Appeals for the Federal Circuit affirmed two PTAB final written decisions holding all challenged claims of Merck’s US Patent Nos. 7,713,947 and 8,377,903 unpatentable as obvious and clarified how the phrase “by another” in pre-AIA 35 U.S.C. §§ 102(a) and (e) applies when a prior-art reference and the challenged patent share overlapping inventors.
Background and the PTAB proceedings
Merck Serono S.A. and Hopewell Pharma Ventures, Inc. develop therapies for multiple sclerosis (MS).1 Merck held US Patent Nos. 7,713,947 and 8,377,903, covering a dosing regimen for orally administering cladribine for MS treatment.2 In 2023, Hopewell filed petitions for inter partes review (IPR) at the Patent Trial and Appeal Board (PTAB), challenging claims of both Merck patents as obvious over a combination of the Bodor3 and Stelmasiak4 references, both of which disclosed dosing regimens for MS patients.5 Merck argued that the Bodor reference could not be treated as prior art because it was not “by another”; Merck argued that one of the patents’ inventors, De Luca, provided an inventive contribution to the 6-line regimen that appears in the Bodor reference.6
The PTAB rejected Merck’s argument on the law and facts. Legally, the PTAB concluded that Merck was wrong to argue that “a reference’s disclosure of the invention of a subset of inventors is disqualified as prior art against the invention of all the inventors.”7 On the facts, the Board concluded that Merck failed to provide evidence that “De Luca’s contribution was sufficiently corroborated to provide compelling evidence that De Luca did in fact contribute to the six-line disclosure in Bodor.”8 Merck appealed.
Federal Circuit affirms its prior interpretations of “by another” and rejects Merck’s argument
Under pre-AIA § 102(e), a patent is anticipated if “the invention was described in . . . a patent granted on an application for patent by another filed in the United States before the invention by the applicant for patent.”9 “Conversely, absent a statutory bar, one’s own work is not prior art.”10 In pre-AIA practice, § 102(a) printed publications likewise qualify as prior art, and here the Federal Circuit did not differentiate between § 102(a) and § 102(e) when addressing the “by another” issue.11 On appeal in this case, the question presented was “whether and to what extent a disclosure invented by fewer than all the named inventors of a patent may be deemed a disclosure ‘by another’ and thus included in the prior art, or whether the disclosure should properly be treated as ‘one’s own work’ and therefore excluded from the prior art.”12
The answer to this question, the Court explained, turns on “whether the disclosure in the earlier reference . . . evidenced knowledge by ‘another’ before the patented invention.”13 That is, “the disclosure in the reference must reflect the work of the inventor of the patent in question.”14 And where, as here, “the patented invention is the result of the work of joint inventors, the portions of the reference disclosure relied upon must reflect the collective work of the same inventive entity identified in the patent to be excluded as prior art.”15 “That showing may be made by fewer than all the inventors,” the Court continued, “but nonetheless must evince the joint work of them all to avoid being considered a work ‘by another’ under the statute.” Thus, “[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.’"16
Practically, this means that if a patent lists multiple inventors, any earlier document must demonstrate that all those inventors collaborated on the subject matter described in that document. Although evidence of this collaboration may be provided by fewer than all the inventors, it must nonetheless establish that the invention was the joint work of all inventors named in the patent. Only then will the earlier document not be considered “by another.” This is so “regardless of whether inventors are subtracted from or added to the patent.”17 Thus, the Court rejected Merck’s argument that “adding an inventor (like adding De Luca here) merely indicates that all the inventors of the prior disclosure collaborated with additional inventors.”18
The Federal Circuit also explained the relevant evidentiary standard. Here, De Luca’s contribution needed to be “significant enough, when measured against the full anticipating disclosure, to render him a joint inventor of the applied portions of the reference.”19 This factual finding is governed by the rule of reason, which requires an “evaluation of all pertinent evidence so that a sound determination of the credibility of the alleged inventor’s story may be reached.”20 Merck, as the patent owner, has a “burden of production,” while the burden of persuasion remained with Hopewell.21 Because the PTAB correctly found that Merck failed to carry its burden of production, the Federal Circuit affirmed its decision.
Key Takeaways
- A prior art reference is only excluded as not “by another” if the inventors are identical between the relied-upon portions of the reference and the patent claim at issue. Adding or subtracting inventors—no matter the direction—means the reference is “by another.”22
- To exclude a reference on “by another” grounds, the patentee must provide corroborated, credible evidence that all listed inventors on the patent made a sufficiently significant contribution to the relied-upon portions of the reference to be considered joint inventors of those portions of the reference. General project involvement or department representation will not suffice.23
1 Serono S.A. v. Hopewell Pharma Ventures, Inc., No. 2025-1210 (Fed. Cir. Oct. 30, 2025), Slip Op. at 3.
2 Id. at 6-7.
3 Bodor, et al., “Oral Formulations of Cladribine,” Int’l Pub. No. WO 2004/087101, published Oct. 14, 2004 (“Bodor”).
4 Zbigniew Stelmasiak, et al., A pilot trial of cladribine (2-chlorodeoxyadenosine) in remitting-relapsing multiple sclerosis, 4 Med. Sci. Monit. 1, 4 (Mar. 1, 1998) (“Stelmasiak”).
5 Serono, at 4-5.
6 Id. at 8.
7 Id.
8 Id.
9 35 U.S.C. § 102(e) (emphasis added).
10 Serono, at 10 (citation omitted).
11 Id. at 11 n.9.
12 Id. at 11.
13 Id. at 15.
14 Id. at 21.
15 Id.
16 Id. at 21-22.
17 Id. at 22.
18 Id. at 21.
19 Id. at 26.
20 Id. at 25-26.
21 Id. at 27.
22 Id. at 12-22.
23 Id. at 26.
Hejir Rashidzadeh (White & Case, Law Clerk, Washington, DC) co-authored this publication.
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