On 2 July 2025, the Enlarged Board of Appeal of the European Patent Office ("EPO"), in its decision G 1/23, clarified whether a product already placed on the market, but whose internal structure cannot be analysed or reproduced by the skilled person, may nevertheless be excluded from the state of the art in the assessment of inventive step. In doing so, the Board added a new dimension to the ongoing debate following decision G 1/92.
The dispute giving rise to the decision concerned opposition proceedings initiated by Borealis against European patent EP 2 626 911 ("EP911"), owned by its competitor Mitsui Chemicals, which related to a solar cell encapsulant material and a solar cell module. Borealis argued that ENGAGE®️ 8400, a polymer marketed by the patentee, was commercially available at the filing date of EP911 and therefore had to be taken into account as prior art in the assessment of inventive step.
Although both parties agreed that ENGAGE®️ 8400 was a complex polymer, that its manufacturing process was not publicly available, and that the complete reproduction of a complex polymer (even if its final product could be analysed by the skilled person) was not straightforward, they diverged in their interpretation of the much-debated G 1/92 holding: "The chemical composition of a product is considered part of the state of the art once the product itself has been made available to the public and can be analysed and reproduced by the skilled person."
The patentee, relying on a narrow reading of G 1/92, argued that since ENGAGE®️ 8400 could not be fully reproduced by the skilled person, it should not be considered part of the prior art at all. Borealis, by contrast, contended that G 1/92 should be interpreted more broadly: any characteristics of a product that was publicly available before the filing date and could be analysed, should form part of the prior art, even if the product could not be fully reproduced.
Although the Opposition Division initially rejected Borealis's inventive-step objections, the case was taken to the Board of Appeal, which decided to refer the following questions to the Enlarged Board of Appeal:
- Is a product put on the market before the date of filing of a European patent application to be excluded from the state of the art within the meaning of Article 54(2) EPC for the sole reason that its composition or internal structure could not be analysed and reproduced without undue burden by the skilled person before that date?
- If the answer to question 1 is no, is technical information about said product which was made available to the public before the filing date (e.g. by publication of technical brochure, non-patent or patent literature) state of the art within the meaning of Article 54(2) EPC, irrespective of whether the composition or internal structure of the product could be analysed and reproduced without undue burden by the skilled person before that date?
- If the answer to question 1 is yes or the answer to question 2 is no, which criteria are to be applied in order to determine whether or not the composition or internal structure of the product could be analysed and reproduced without undue burden within the meaning of opinion G 1/92? In particular, is it required that the - 3 - G 0001/23 composition and internal structure of the product be fully analysable and identically reproducible?"
In its assessment, the Enlarged Board of Appeal rejected the idea that a product already on the market could be treated "as if it did not exist," noting that such an approach would not reflect practical reality. The Board held that G 1/92 required broader interpretation. Whether a marketed product can be reproduced is, according to the Enlarged Board, a matter of proof to be assessed in each individual case; but the mere fact that it cannot be reproduced does not justify excluding it from the state of the art.
Most importantly, with G 1/23, the test of "analysability + reproducibility" was abandoned. The Enlarged Board considered that analysability (i.e., the ability of the skilled person to determine the product's composition/properties through reasonable effort) is sufficient for the product to belong to the state of the art. Reproducibility is no longer a mandatory requirement. According to the decision, if a product is publicly available and the skilled person can understand its features—wholly or in part—that knowledge forms part of the prior art. Moreover, "reproduction" must be understood broadly: it does not mean that the skilled person must be able to manufacture the product themselves, but rather that they must be able to obtain or possess it (for example, by purchasing it). Thus, a marketed product cannot be excluded from the prior art merely because its full composition or structure cannot be completely analysed or identically reproduced.
The finding of G 1/23—that products already on the market but not fully reproducible by the skilled person are nevertheless prior art—has undeniable potential to reshape both claim-drafting practices and even marketing strategies of patent proprietors. It is beyond doubt that this decision will reverberate in the patent world for years to come.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.
