New decision G 1/23 of the Enlarged Board of Appeal of the EPO

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Publicly available product is prior art, even when not reproducible

In decision G 1 /23 issued on July 2, 2025, the Enlarged Board of Appeal of the European Patent Office was confronted with the question of whether a product put on the market is considered prior art regardless of enablement. In particular, the referral asks whether the non-enabling prior use of a product excludes the composition of the product, and also the product as such, from the prior art.

Key takeaways of the decision

  • Availability is sufficient: A product that was made publicly available before the filing date (e.g. through sales) is considered part of the prior art, even if it could not be technically analyzed or reproduced at that time.
  • No reproducibility requirement: Article 54(2) EPC does not require that a skilled person must have been able to reproduce the product before the filing date. Major impact on inventions in the fields of chemistry and materials science, where the internal composition is often hard to detect.
  • Possible impact also on computer-implemented inventions, where it is rather difficult to verify the exact code and algorithms or for prototypes delivered to clients under agreements forbidding reverse-engineering or internal manipulation.

Particulars of the case

The case originated from an opposition by Borealis GmbH (Opponent) against the European Patent No. 2 626 911, held by Mitsui Chemicals, Inc. and Mitsui Chemicals ICT Materia, Inc. (Patent Proprietors), concerning a solar cell sealing material.

At the center of the dispute was the commercially available product “ENGAGE® 8400,” a complex polymer used for sealing in solar modules. Although this product had been made commercially available before the priority date of the opposed patent, it was not possible to fully analyze its chemical composition and thus to reproduce it by the relevant date.

Against this background, it was controversially discussed whether such a (disclosed but allegedly non-reproducible) product could be considered prior art when assessing inventive step.

In previous decision G1/92, it had been ruled that “The chemical composition of a product is state of the art when the product as such is available to the public and can be analysed “and reproduced” by the skilled person, irrespective of whether or not particular reasons can be identified for analysing the composition”. There, the Enlarged Board of Appeal held that where it is possible for the skilled person to discover the composition or the internal structure of the product “and to reproduce it” without undue burden, then both the product and its composition or internal structure become state of the art”. This lead to the possibility of excluding from the prior art non-reproducible disclosures, including non-reproducible public prior uses.

The case was referred to the Enlarged Board of Appeal to seek clarification as to whether the non-enabling prior use of a product excludes the composition of the product from the prior art or whether it also excludes the product per se.

This is of significance, because if the product per se is excluded it cannot be used as a starting point for an inventive step analysis. The referral also seeks clarification over the definition of enablement with respect to the prior use of a product, and particularly whether “enablement” requires that the skilled person be able to fully analyse and reproduce the exact same product.

The decision and its aftermath

In new decision G 1/23, the Enlarged Board of Appeal sets the criterion that the chemical composition of a product is part of the state of the art when the product as such is available to the public and can be analysed by the skilled person, irrespective of whether or not particular reasons can be identified for analysing the composition.

Accordingly, while decision G1/92 is not being overturned, it is being partly amended in that the “reproducibility requirement” is no longer used when assessing whether a public prior use is deemed publicly available and hence belongs to the prior art.

In reaching this decision, the Enlarged Board of Appeal emphasized that the prior art refers to abstract technical teachings or information, which, once made public, do not disappear even if the physical carrier (e.g., the product itself) is no longer available. Problems in proving what was disclosed by a product (e.g., if it is no longer available) are issues of evidence, not reasons to deny its prior art status.

While a non-reproducible product now belongs to the state of the art and could potentially destroy novelty, it does not necessarily follow that it will be equally relevant to assessments of inventive step. As the Enlarged Board of Appeal explicitly found, the skilled person may still disregard such a product as relevant prior art for good reason. This is because the assessment of inventive step depends on the context and is influenced by numerous factors, including the general knowledge of the skilled person, the analyzable properties of the product and practical limitations.

This triggers the question of whether analysis of a chemical product, as considered in G 1/23. may be handled on the same footing as analysis of a (compiled) software product available on the market in terms of determining whether its internal functioning (e.g. underlying algorithm) “can be analysed”. It should be borne in mind that decompiling a software product is allowed in the EU only under special circumstances, since reproduction and translation of any code form (i.e. de-compilation) is generally seen as an exclusive right of the copyright owner (see CJEU October 6, 2021, ECLI:EU:C:2021:811 (Top Systems/Belgian State) on Directive 2009/24/EC). This may influence the assessment of what the skilled person might be expected to do. Notably, cooperation and license-agreements may also explicitly ban decompiling and reverse-engineering. By contrast, in chemistry, analysis of a chemical product typically is considered as belonging to the standard abilities of the skilled person and is not legally restricted.

Impact on Practice

  • For examination proceedings: Novelty can now also be destroyed by products whose exact composition cannot be reconstructed or reverse-engineered – the sole decisive factor is their public availability.
  • For patent applicants: Exercise caution when marketing innovative products before the filing date of a first patent application, even when they are difficult to analyze, as they may also be considered novelty-destroying. Early filing of the patent application has thereby become even more important, as there will be even less chances to still a product once put on the market.
  • For search and opposition: Pay increased attention to actual products on the market, regardless of their complete technical disclosure.
  • For licensing agreements, cooperations and delivery of customer prototypes, especially for mechanical and software products: Try including in the agreement a clause explicitly forbidding de-compilation and reverse-engineering.