UPC Aligns With the EPO in Allowing Functional Antibody Claims
In Short
The Background: While the U.S. Supreme Court rejected Amgen's functionally defined anti-PCSK9 antibody claims based on its high bar for enablement, the European Patent Office ("EPO") found such broad antibody claims allowable. Amgen's battle was also fought at the Unified Patent Court ("UPC"), with the first instance denying an inventive step.
The Result: The UPC Court of Appeal ("CoA") recently overturned the first-instance decision. With its ruling on November 25, 2025 (UPC_CoA_529/2024), the UPC aligns its standard on sufficiency for functionally defined antibody claims with that established by the EPO jurisprudence, while rejecting a strict adherence to the EPO's "problem-solution" approach for assessing an inventive step.
Looking Ahead: The UPC and EPO are now aligned on the sufficiency standard for broad functional antibody claims, in sharp contrast to the stricter U.S. approach. For global life science companies, Europe remains a critical venue where well-supported functional antibody claims, such as epitope-defined claims, are viable.
Introduction
Following the U.S. Supreme Court's Amgen Inc. v. Sanofi, 598 U.S. 594 (2023) ruling, which invalidated antibody genus claims for lacking enablement, the U.S. drafting strategy has shifted toward structural definitions, including complementarity-determining regions and variable domains. By contrast, EPO continues to allow functional antibody claims, including those defined by epitopes.
Amgen's battle in Europe concerns its European patent EP3666797. Claim 1 functionally defines an anti-PCSK9 antibody genus by: (i) the region to which it binds, namely the catalytic domain of a PCSK9 protein, and (ii) its function to prevent or reduce the binding of PCSK9 to LDLR. The patent was revoked by the Munich Central Division of the UPC in the first-instance revocation proceedings in July 2024 but was maintained as granted in May 2025 after the first-instance opposition proceedings at the EPO. The UPC CoA recently issued its landmark decision on the UPC revocation action, overturning the decision of the Munich Central Division. The UPC's approach to sufficiency reiterates the established EPO principle that sufficiency is satisfied if the patent shows at least one way of performing the invention. Furthermore, likely welcomed by several national jurisdictions, the UPC indicates that EPO's "problem-solution" approach may not be the only way for assessing an inventive step.
On Sufficiency
The UPC's approach to sufficiency reiterates the established EPO principle that sufficiency is satisfied if the patent shows at least one way—or one technical concept—of performing the invention, and that functional features do not require instruction for "each and every conceivable embodiment." A "reasonable amount of trial and error" is tolerable, and occasional failure is part of the scientific work. The burden lies with the challenger to prove insufficiency.
According to the U.S. Supreme Court, the effort required to screen and produce all antibodies within a genus claim constitutes "undue experimentation" and thus triggers a lack of enablement rejection. In contrast, the EPO and the UPC accept that generating new antibodies under a functional definition is within the routine capabilities of the skilled person, provided that the patent discloses a "technical concept" for doing so. The time required for such production is not, in itself, decisive.
On Inventive Step
The CoA's approach to an inventive step is equally notable. It considers that different approaches, whether "holistic" or "problem-solution," when properly applied, should and generally lead to the same conclusion.
The CoA emphasizes a case-by-case evaluation of the evidence to determine whether the skilled person possessed a "reasonable expectation of success" or merely a "hope to succeed." It also stresses a careful distinction between what "could" and what "would" have led the skilled person to the invention. These follow some well-established EPO principles on assessing non-obviousness and are favorable for patentees.
Four Key Takeaways
- The recent UPC CoA ruling clarifies and reinforces the standards governing the validity of broad functional antibody claims in Europe.
- In contrast to the U.S. practice, there is no requirement in Europe to show that the skilled person can produce each and every embodiment of the invention within the claimed scope.
- The UPC does not consider the EPO "problem-solution" approach a necessity for assessing an inventive step, but rather endorses an evidence-based, case-by-case approach.
- This landmark decision reaffirms a permissive stance on functional antibody claims in Europe. Innovators may pursue genus antibody claims defined by functional features before EPO and UPC, consistent with prevailing case law and practice.
