This article compares how claim interpretation is approached under the European Patent Convention (EPC) and by the European Patent Office (EPO) following G 1/24, and how the Court of Appeal of the Unified Patent Court (UPC) is applying Article 69 EPC and its Protocol in both infringement and validity proceedings.
It is trite law that claims define the scope of protection. The real difficulty arises where a claim feature appears clear on its face, yet the description gives it a broader (or different) technical meaning that still makes sense to the skilled person. Should the description influence interpretation in such cases, or only where the claim wording is ambiguous? That question lies at the heart of both G 1/24 and the UPC Court of Appeal’s jurisprudence.
As we will discuss, both clearly reject literalism and standalone claim reading. Yet, whilst they start from the same legal foundations, they reveal different interpretative instincts, with real consequences for drafting, prosecution and litigation.
1. G1/24: claims are primary, description and drawings always matter
In G 1/24, the EPO Enlarged Board of Appeal was asked to clarify whether, and to what extent, the description and drawings may be consulted when interpreting claims for the purpose of assessing patentability.
1.1 Background and referral
The referral arose from decision T 439/22, concerning Philip Morris’ patent for a heated aerosol‑generating article and the meaning of the term “gathered sheet”. The key issue was whether claim 1 was novel over document D1 disclosing a similar heated aerosol-generating article, but with a wrapped sheet. The proprietor relied on the usual technical meaning of the term “gathered sheet” to establish novelty. The opponent argued that the description defined the term more broadly, yet in a still technically sensible meaning, allegedly encompassing prior‑art embodiments (a rolled/wound tobacco sheet and a cylindrical plug of homogenised tobacco material as disclosed in D1 and D2 respectively).
The question was thus whether to consult the description to interpret an otherwise clear term in the claims. There have always been two approaches on the matter: one favouring reading that a claim on its own when the features are clear, and one advocating that the description and drawings always need to be consulted. The referring Board therefore asked the Enlarged Board to answer:
- Q1: Is Article 69(1), second sentence, EPC and Article 1 of the Protocol on the Interpretation of Article 69 EPC to be applied to the interpretation of patent claims when assessing the patentability of an invention under Articles 52 to 57 EPC?
- Q2: May the description and figures be consulted when interpreting the claims to assess patentability and, if so, may this be done generally or only if the person skilled in the art finds a claim to be unclear or ambiguous when read in isolation?
- Q3: May a definition or similar information on a term used in the claims which is explicitly given in the description be disregarded when interpreting the claims to assess patentability and, if so, under what conditions?
1.2 Decision of the Enlarged Board
The Enlarged Board considered that neither Article 69 European Patent Convention (EPC) and Article 1 of the Protocol on the interpretation of Article 69 EPC (Protocol) (associated with infringement before the courts), nor Article 84 EPC (formal in nature and providing no interpretative methodology) provides for an entirely satisfactory basis for claim interpretation when assessing patentability.
Formally, this would have pointed towards a negative answer to Question 1. The Enlarged Board nevertheless clarified that, in practice, it makes no material difference whether claim interpretation for patentability is anchored in Article 69 EPC or Article 84 EPC. The Boards of Appeal have long applied the same interpretative principles when assessing patentability under Articles 52 to 57 EPC. There is therefore an established body of case law from which the applicable principles of claim interpretation can be derived.
Against that background, the Enlarged Board held that the claims are the starting point and basis for assessing patentability, and that the description and drawings must always be consulted when interpreting the claims, even where the claim wording appears clear when read in isolation.
1.3 Aftermath and emerging EPO picture
Oral proceedings in the referring case T 439/22 took place in December 2025. According to the minutes, the patent was revoked for lack of novelty over D1. Although the written reasons are not yet available, the outcome suggests that the Board relied on G 1/24 to interpret the term “gathered sheet” in light of the broader definition given in the description, thereby denying patentability. This has potentially far-reaching consequences, particularly where descriptive definitions extend beyond the term’s usual technical meaning.
At the same time, post-G 1/24 decisions already illustrate that the obligation to “consult” the description does not operate mechanically. In T 1561/23, the Board held that consulting the description does not require that a definition contained therein must be applied. Although the applicant relied on a descriptive definition distinguishing “additional functions” from prior-art “tasks”, the Board considered the two to be technically indistinguishable and found the claims to lack novelty. In the Board’s view, the description merely provided examples and did not establish a meaningful conceptual distinction.
The emerging case law confirms that “consulting” the description does not equate to either systematically narrowing or systematically broadening claim scope. Rather, the description may influence interpretation where it supports a technically sensible reading from the perspective of the skilled person, whilst not justifying a restriction of clear claim language to specific embodiments. Conversely, consultation may lead to broader interpretations where the patent itself defines a term more expansively.
2. UPC Court of Appeal: consolidation and refinement of claim construction under Article 69 EPC
2.1 NanoString v 10x Genomics
The UPC Court of Appeal addressed claim construction at a very early stage in NanoString v 10x Genomics (UPC_CoA_335/2023, 26 February 2024). The appeal resulted from the order of the Munich Local Division of 19 September 2023 (UPC_CFI_2/2023) granting NanoString a preliminary injunction against 10x Genomics. On appeal, 10x Genomics argued that the patent was more likely than not invalid for lack of inventive step over the prior art.
The Court of Appeal laid down principles that now form the backbone of UPC claim construction: the patent claim is not merely the starting point but the decisive basis for determining the scope of protection under Article 69 EPC and the Protocol. Claim interpretation does not depend solely on the strict, literal meaning of the wording, and the description and drawings must always be used as explanatory aids, not only to resolve ambiguities. At the same time, this does not reduce the claim to a mere guideline: the protected subject-matter is that which, after examination of the description and drawings, emerges as what the proprietor seeks to protect, while remaining anchored in the claim as the decisive reference point. Interpretation is carried out from the standpoint of the skilled person, balancing adequate protection for the proprietor with legal certainty for third parties. These interpretative principles apply equally to infringement and validity.
The appeal concerned inventive step in preliminary injunction proceedings. On this basis, the claims were deemed more likely than not to lack inventive step, and the Court revoked the preliminary injunction. Taking into account the definitions in the description, the feature “in a cell or tissue sample” was seen as only encompassing a sample which is still “structurally recognisable as a cell or tissue”, and therefore the claims were deemed new over D6, but not inventive.
2.2 Refinements in further Court of Appeal decisions
Since then, the Court of Appeal has issued a series of decisions further shaping UPC claim interpretation, including Alexion v Amgen (UPC_CoA_405/2024, 20 December 2024), Alexion v Samsung Bioepis (UPC_CoA_402/2024, 20 December 2024), Insulet v EOFlow (UPC_CoA_768/2024, 30 April 2025), Abbott v Sibio (UPC_CoA_382/2024, 14 February 2025), and the merits judgments in Amgen v Sanofi & Regeneron (UPC_CoA_528/2024 & UPC_CoA_529/2024, 25 November 2025) and Edwards v Meril (UPC_CoA_464/2024 ff., 25 November 2025). These decisions lead in our view to seven takeaways.
2.2.1 The claim is decisive — but not autonomous
Across all decisions, the Court of Appeal consistently stresses that the claim is the decisive basis for defining the scope of protection. However, this decisiveness does not mean that the claim can be read in isolation. The description and drawings are not secondary sources to be consulted only in cases of ambiguity, they are an integral part of the interpretative exercise in every case, not merely in cases of ambiguity. This positions the UPC away from any “plain meaning” claim construction doctrine, whilst at the same time preventing the description from displacing or rewriting the claim language.
2.2.2 Interpretation is anchored in the skilled person — not in experts
Insulet v EOFlow makes explicit what is implicit elsewhere: claim construction is a matter of law, not of fact. The “person skilled in the art” is a normative legal construct, not a proxy for whichever expert is most persuasive. Expert evidence may inform the Court, but it cannot substitute the Court’s own interpretative responsibility. This limits attempts to smuggle claim construction through technical evidence and reinforces judicial control over the scope of protection.
2.2.3 No “correction by interpretation” except in truly exceptional cases
The Alexion decisions (Alexion v Amgen and Alexion v Samsung Bioepis) establish a particularly strict standard for alleged drafting errors. A linguistic error, spelling mistake, or any other inaccuracy in a patent claim can only be corrected by way of interpretation if the existence of an error and the precise way to correct it are sufficiently certain to the average skilled person. This standard combines adequate protection for the patent proprietor with a reasonable degree of legal certainty for third parties. This curtails creative reinterpretations at the enforcement stage and places the drafting burden squarely back on patentees.
2.2.4 Functional language is construed broadly, but not loosely
In Abbott v Sibio, the Court confirms that functional features are, in principle, construed as covering any means suitable for performing the stated function, not merely the embodiments disclosed. However, this breadth flows from the claim language itself as understood by the skilled person, and the description generally presents the patent’s “lexicon”. The decision therefore reinforces text-anchored breadth, rather than description-driven expansion.
2.2.5 Feature-by-feature dissection is a tool, not a method
The merits judgment in Amgen v Sanofi & Regeneron warns against an overly atomistic reading of claims. Breaking claims into features may assist analysis, but interpretation must ultimately return to the claim as a whole, read in its technical and contextual setting. This aligns the UPC closely with established EPO practice and discourages litigation strategies that seek to create artificial distinctions by over-fragmentation.
2.2.6 Prosecution history: no estoppel, but no clean slate either
A nuanced development emerges from Alexion (Alexion v Amgen and Alexion v Samsung Bioepis). Whilst the Court of Appeal does not apply a US-style prosecution history estoppel, it accepts that the applicant’s assertions during the grant proceedings, and in particular the Technical Board of Appeal’s endorsement thereof, can be seen as an indication of the view of the person skilled in the art at the filing date. In other words: prosecution history is not binding, but it is not irrelevant either. Where a patentee advances an interpretation before the UPC that is difficult to reconcile with a position successfully defended before the EPO, the Court may treat that inconsistency as evidence against the patentee’s construction.
2.2.7 One interpretation for infringement and validity
Finally, all of these decisions consistently reaffirm that the same interpretative principles apply to infringement and validity. The understanding of a claim by the skilled person must be consistent for all purposes of the evaluation of infringement and validity. There is no room for “dual” constructions depending on the procedural posture. This reinforces legal certainty and prevents strategic oscillation between narrow and broad readings.
2.3 Emerging picture
The emerging picture is not merely moderation between extremes, but discipline: disciplined anchoring in the claim, disciplined use of the description, disciplined reliance on expert evidence, and disciplined treatment of procedural history. The UPC Court of Appeal is shaping a claim-construction doctrine that is recognisably EPC-based, judicially controlled, and resistant to litigation-driven elasticity.
3. EPO and UPC: harmony in law, divergence in instinct
At a doctrinal level, there is no real conflict between G 1/24 and the UPC Court of Appeal’s case law. Both reject literalism or standalone claim-reading, and insist on a skilled person reading informed by the full disclosure of the patent.
The difference lies in scope and emphasis. The EPO deals with patentability only, while the UPC deals with both patentability and infringement. Further, G 1/24 is constitutional in tone, setting boundaries and safeguarding systemic coherence within the EPC framework. The UPC Court of Appeal, by contrast, applies those same principles in a distinctly operational manner, focused on producing technically sensible and litigation ready outcomes.
4. Take‑aways for patent drafting and UPC litigation
It remains to be seen how both decisions will be applied in the future, but in any case, for patent attorneys, it triggers some alarm bells when drafting future-proof applications, and possibly opens a new line of attack for litigators.
For patent attorneys: Putting a broad definition of an otherwise well-understood feature in the specification could potentially lead to said feature being interpreted in the broader way, possibly leading to patentability issues. However, putting in alternatives of the claimed feature in the description may be needed for proving equivalence. In order to safeguard the latter, it could be a safer option to separately define said equivalents rather than to include them in the actual definition of the feature.
Alternatively, when broad definitions were used (i.e. in older applications) one could opt to trim the definition and bring it in line with the true intended meaning in the art of said feature, taking care of course not to offend Article 123(2) EPC (added matter).
Additionally, as confirmed by post G1/24 decision T 1561/23, the term ‘consult’ seems to leave some freedom on whether a broad description definition overrules a clear feature in the claims and has so far been used differently when applied to deny versus to prove patentability.
For patent litigators: Although the Court of Appeal decisions could limit the ‘Angora cat’ paradox in future patents, many granted patents contain expansive descriptive passages that may be leveraged in validity attacks. However, since the rules on interpretation of claims apply equally to the assessment of the infringement and the validity of a European patent, it is important to keep in mind that when such a validity attack would fail, it could lead to a broader scope of protection in terms of infringement.
