EPO Enlarged Board of Appeal decision G1/23 removing the reproducibility criterion of G1/92 from commercially available products as prior art

On July 2, 2025, the landmark decision G1/23 “Solar Cell” was published by the Enlarged Board of Appeal. HOFFMANN EITLE was involved in this case as representative for our long-standing client Mitsui Chemicals, Inc. 

According to the decision, a product put on the market cannot be excluded from the state of the art solely because its composition or internal structure could not be analysed and reproduced by a skilled person. All technical information about such a product also belongs to the state of the art. 

This decision is a major departure from G1/92, where it was previously held that a product only becomes prior art if it is possible for the skilled person to discover its composition or internal structure and reproduce it. G1/23 supersedes G1/92 and states that irrespective of the reproducibility criterion, said product and technical information about it is prior art if it can be obtained and possessed.

Notably though, the Enlarged Board´s decision highlighted that even though such products are prior art, this does not mean that such a product is necessarily relevant prior art. Depending on the circumstances, a product may be pertinent with regard to novelty but may not be suitable as a starting point for an inventive step assessment, as a skilled person´s inability to reproduce the product may be relevant information that has to be considered in the selection of the closest prior art.

So far, this aspect of the decision has produced mixed results in citing decisions. In a related case (T 1719/21), the referring Board considered the non-reproducible product (a specific polymer grade) to represent the closest prior art, as it was in the same technical field and used for the same purpose. The Board rejected the argument that the product would not qualify as closest prior art because it is not a promising starting point for further developments that require changes to the (unknown) process for preparing the product. Starting from the commercial product, the claimed subject matter was, however, still regarded to be inventive.

Another decision of interest in this respect is T 1044/23. Also in this case, the Board considered non-reproducible commercial products (DMDA resins) to form the closest prior art, and the Board was unable to identify a technical effect that is caused by the distinguishing feature (density) over the commercial product. The Board nonetheless considered the claimed subject matter to be inventive, as the Opponent could not show that the skilled person knew how to obtain the claimed material, holding that “whether the person skilled in the art would be able to identify the measures which would, starting from the DMDA resins, lead to a polyethylene composition that meets the parametric definition of claim 1 without having to resort to an undue amount of experimental work remains a matter of conjecture.” 

In light of the latter decision, it has to be expected that there may be a shift in the argument, away from the question whether the prior art is reproducible towards the question whether the claimed subject matter is (re-)producible based on the prior art and common knowledge. Arguments in relation to (re-)producibility may thus not fully disappear from opposition proceedings before the EPO.