IP Law Daily, PATENT—Fed. Cir.: Merck Serono’s cladribine patents correctly invalidated as obvious, (Oct 30, 2025)

By Saurabh Kashyap, B.A., M.A., LL.B., LL.M.

Prior art by a different inventive entity rendered Merck’s multiple-sclerosis treatment patents obvious under pre-AIA §§ 102 and 103.

The U.S. Court of Appeals for the Federal Circuit affirmed the Patent Trial and Appeal Board’s (PTAB) decision invalidating two patents owned by Merck Serono S.A. that covered oral dosing regimens of cladribine for treating multiple sclerosis (MS). The appellate court upheld the PTAB’s findings that the patents were obvious in view of prior art references and that a prior publication, despite some overlapping inventors, constituted prior art “by another” under pre-AIA 35 U.S.C. §§ 102(a) and (e) (Merck Serono S.A. v. Hopewell Pharma Ventures, Inc., Nos. 2024-1745, 2024-1746 (Fed. Cir. Oct. 30, 2025)).

Background. The appellant, Merck Serono S.A., is a biopharmaceutical company based in Switzerland engaged in developing therapies for autoimmune and neurological conditions. The appellee, Hopewell Pharma Ventures, Inc., is a biotechnology company involved in pharmaceutical development and patent challenges. The dispute arose from a prior collaboration between Serono (later acquired by Merck) and Ivax Corporation in the early 2000s. Under this collaboration, Ivax handled the formulation of oral cladribine while Serono oversaw clinical testing. Both entities exchanged confidential data during the developmental phase.

The challenged patents, U.S. Patent Nos. 7,713,947 (the ’947 patent) and 8,377,903 (the ’903 patent), both titled “Cladribine Regimen for Treating Multiple Sclerosis,” relate to methods of treating MS by orally administering cladribine, a purine nucleoside analog, in cyclical dosing schedules. Representative claim 36 of the ’947 patent recites oral administration of cladribine in a total dosage of about 1.7 to 3.5 mg/kg over a short induction period, followed by extended cladribine-free intervals and subsequent maintenance courses. Both patents share the same priority date of December 22, 2004, and list four inventors—Drs. De Luca, Ythier, Munafo, and Lopez-Bresnahan.

Hopewell Pharma filed two inter partes review (IPR) petitions asserting that all challenged claims were unpatentable as obvious over two prior art references: Bodor et al. (WO 2004/087101) and Stelmasiak et al. (1998). Bodor disclosed an oral cladribine-cyclodextrin complex administered for two months, followed by ten months without treatment, while Stelmasiak described cladribine therapy for MS involving repeated cycles of monthly treatment and drug-free intervals.

Merck argued that Bodor could not qualify as prior art because one of its inventors, Dr. De Luca, had contributed to developing Bodor’s dosing regimen through his collaborative work during the Serono–Ivax partnership. The PTAB rejected that claim, finding no corroborated evidence that De Luca had made a significant inventive contribution to Bodor. The Board concluded that Bodor was “by another” and, when combined with Stelmasiak, rendered Merck’s claimed regimen obvious. Merck appealed.

“By another.” The Federal Circuit began by reaffirming the long-established principle that a reference qualifies as prior art "by another" if its inventive entity differs in any respect from that of the challenged patent. Merck argued that an overlap of even one common inventor suffices to make the reference the inventor's work, thereby excluding it as prior art. The court rejected that interpretation, noting that the law requires complete identity of inventive entities to disqualify a reference. This principle, first articulated in In re Land, 368 F.2d 866 (CCPA 1966), has remained consistently applied through subsequent decisions. Those cases collectively hold that if the listed inventors differ, even partially, the earlier disclosure is “by another.”

Applying this rule, the court observed that Bodor listed Drs. Bodor and Dandiker as inventors, while the Merck patents listed De Luca, Ythier, Munafo, and Lopez-Bresnahan. Because the inventive entities were not identical, Bodor was treated adequately as prior art "by another."

APA and MPEP. Merck asserted that the PTAB violated the Administrative Procedure Act by adopting a rule inconsistent with the Manual of Patent Examining Procedure (MPEP). It pointed to MPEP §§ 2132.01 and 2136.05(b), which state that “an inventor’s or at least one joint inventor’s own work” is not prior art. The Federal Circuit rejected this claim, emphasizing that MPEP § 2136.04 expressly follows the Land decision, stating that “the inventive entity is different if not all inventors are the same.” The court reiterated that the MPEP lacks the force of law and cannot override judicial precedent, citing Molins PLC v. Textron, Inc., 48 F.3d 1172 (Fed. Cir. 1995).

The court further distinguished In re Kaghan, 387 F.2d 398 (CCPA 1967), on which Merck relied, explaining that Kaghan dealt with procedural adherence to the MPEP rather than substantive patentability standards.

Inventive contribution. Merck next contended that the PTAB imposed an excessively rigid corroboration requirement to determine whether Dr. De Luca contributed to Bodor’s inventive subject matter. It invoked the “rule of reason” standard recognized in Ethicon, Inc. v. U.S. Surgical Corp., 135 F.3d 1456 (Fed. Cir. 1998), which requires a flexible assessment of corroborating evidence. The court disagreed, holding that the PTAB correctly demanded corroboration of a “significant inventive contribution,” consistent with Duncan Parking Techs. Inc. v. IPS Grp. Inc., 914 F.3d 1347 (Fed. Cir. 2019).

The record, the court observed, showed only that De Luca participated in joint research meetings during the Serono–Ivax collaboration. No contemporaneous documentation, communication, or testimony confirmed that he contributed intellectually to the six-line dosing regimen disclosed in Bodor.

Burden of proof. Further, Merck argued that the PTAB improperly shifted the ultimate burden of persuasion to the patent owner. The court clarified that the Board had merely placed a burden of production on Merck once Hopewell made a prima facie showing that Bodor was prior art, while the ultimate burden of persuasion remained with Hopewell. This allocation, the court noted, did not violate the APA.

Obviousness. Turning to the merits, the Federal Circuit upheld the PTAB’s finding that the combination of Bodor and Stelmasiak rendered the claimed cladribine regimen obvious under § 103. The PTAB found that Bodor disclosed an oral dosing regimen with long off-drug intervals and that Stelmasiak disclosed cladribine retreatment following similar intervals. A skilled artisan, recognizing the chronic and relapsing nature of MS, would have been motivated to combine these teachings to produce a cyclical dosing method, with a reasonable expectation of success.

The court agreed, relying partly on expert testimony that clinicians routinely adjust dosing regimens based on patient relapse patterns and pharmacodynamic responses. It held that Merck's claimed regimen did not include any unique "automatic retreatment" feature and that converting between weight-based and fixed dosing amounts was a routine calculation insufficient to confer patentability. The court cited KSR Int’l Co. v. Teleflex Inc., 550 U.S. 398 (2007), in reaffirming that combining known methods to yield predictable results is unpatentable.

Thus, the Federal Circuit affirmed the PTAB’s decision holding that the ’947 and ’903 patents are invalid as obvious over Bodor and Stelmasiak.

The Case is Nos. 24-1745, 24-1746.

Judge: Linn, R.

Attorneys: Mark Christopher Fleming (Wilmer Cutler Pickering Hale and Dorr LLP) for Merck Serono S.A. John Christopher Rozendaal (Sterne Kessler Goldstein & Fox PLLC) for Hopewell Pharma Ventures, Inc.

Companies: Merck Serono S.A.; Hopewell Pharma Ventures, Inc.

MainStory: TopStory Patent FedCirNews USPTO