current affairs

Enlarged Board
of Appeal
broadens concept of
‘prior art’
in G 1/23

On 2 July 2025, the Enlarged Board of Appeal of the European Patent Office (EPO) ruled in case G 1/23, also known as the ' Solar Cell' case. This decision clarifies whether a marketed product belongs to the prior art even if it cannot be fully analyzed or imitated. This is especially relevant for complex chemical products whose exact composition and method of production are not publicly known, even though the product is already on the market.

Inventions are patentable, according to the EPO, if they are new and inventive with respect to the prior art. According to the EPO, prior art includes everything that has been disclosed before the filing date of a patent application, for instance through publication, use or sale. The central question in G 1/23 was whether a commercially available product, whose internal composition is unknown and not reproducible, also belongs to the prior art.

Available on the market

The case arose out of a dispute over a polymer material used in solar cells. This material was available on the market before the filing date of the patent application, but the exact composition could not be determined and replicated by one skilled in the art at that time. The question was whether such a material could belong to the prior art, as an earlier decision of the Enlarged Board of Appeal (G 1/92) stated that this is so only if a product could be analyzed AND reproduced.

In practice, this led to divergent decisions in case law. Some Boards of Appeal stated that products that cannot be fully analyzed or reproduced do not belong to the state of the art.

Broader interpretation

The Enlarged Board has now clarified this. It argues that the term ‘reproducibility’ should be interpreted more broadly. If a product is marketed and physically available to a person skilled in the art, then it is reproducible in the legal sense. Indeed, it is possible to obtain the product repeatedly, even if it cannot be reproduced from basic materials.

In addition, the Court holds that analyzability is not a separate condition. The fact that a product was available to the public - possibly along with technical information - is sufficient for inclusion in the prior art. This applies even if its composition or structure remained unknown. Similarly, the fact that a product is later modified or disappears from the market does not change its status as prior art.

Conclusion and lesson for practice

A product put on the market before the filing date belongs to the prior art, even if it could not be fully analyzed or reproduced. Patent owners must therefore take into account a broad interpretation of the term 'prior art'. What is publicly available counts - even if not all of it is technically understandable.

If you have any questions about this topic, please contact one of our patent attorneys.