An invention is patentable if it is new and involves an inventive step. The state of the art plays a key role here. In its decision G 1/23 of 2 July 2025, the Enlarged Board of Appeal of the European Patent Office (EPO) has now clarified what exactly counts as prior art in an important respect: it deals with the question of whether previously published products whose composition or internal structure cannot be easily analysed and reproduced can be regarded as prior art.

The starting point for decision G1/23 was a previous decision of the Technical Board of Appeal in case T0438/19. The underlying opposition proceedings against the European patent EP 2 626 911 concerned special plastic materials for solar modules.

Specifically, the question was whether the polymer ‘ENGAGE® 8400’, which had already been published and commercially available before the patent application was filed, was to be regarded as prior art simply because of its availability. It was argued that the mere commercialisation of the product ‘ENGAGE® 8400’ did not automatically lead to a sufficient disclosure of the composition. The reproduction of the polymer would not be readily possible for the skilled person without any knowledge of the specific synthesis conditions, as these could not be derived from the available product.

Up to now, the assessment of whether such a product belongs to the state of the art was based on decision G 1/92.

According to G 1/92, a product belongs to the state of the art if:

- it has been made available to the public,

- a person skilled in the art can analyse and reproduce it without unreasonable effort,

- regardless of whether there are particular reasons to analyse the composition.

What is new?

In G1/23, the Enlarged Board of Appeal dealt with the interpretation of G 1/92, in particular with the reproducibility required therein. The main question was whether public availability was sufficient to determine the state of the art or whether technical reproducibility was decisive.

The Enlarged Board of Appeal clarified:

A product placed on the market before the filing date of a European patent application cannot be excluded from the state of the art according to Article 54(2) EPC merely because its composition or internal structure could not be analysed and reproduced by a person skilled in the art before that date.

In particular, the expected reproducibility of the product according to G 1/92 must be understood in a broader sense, namely as the ability of the person skilled in the art to obtain and possess the physical product.

Technical information about such a product published before the filing date also counts as prior art, irrespective of whether the skilled person was able to analyse and reproduce the product and its composition or internal structure before that date.

G 1/23 has far-reaching implications for the assessment of patentability and for opposition and nullity proceedings at the European Patent Office, the Unified Patent Court (UPC) and the national courts.

The decision emphasises the decisive importance of actual accessibility over technical reproducibility and thus aligns the practice of the EPO more closely to the approach of the UPC. It also emphasises the importance of the timing of the patent application in order to avoid disclosure prejudicial to novelty by products, or technical information about these products, that have already been made publicly available before the filing date.