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29 September 2025

G 1/23: EPO Confirms A Product Can Still Be Prior Art Even If It Can't Be Reproduced

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At the beginning of July, the Enlarged Board of Appeal (EBoA) of the European Patent Office (EPO) issued its decision in case G 1/23.
United Kingdom Intellectual Property

At the beginning of July, the Enlarged Board of Appeal (EBoA) of the European Patent Office (EPO) issued its decision in case G 1/23. #

In this decision, it was concluded that commercial products that cannot be reproduced by third parties can still be relevant to the novelty of a patent claim. This has particular relevance in the field of chemistry. In this article, we review the decision and consider what it could mean for patent applicants.

The original opposition #

G 1/23 related to a European patent in the name of Mitsui Chemicals. The patent was granted in December 2015 with claims directed to a material for a solar cell comprising an ethylene/α-olefin copolymer with specific compositional features and properties. In September 2016 an opposition to the grant of this patent was filed by Borealis AG.

In the opposition, Borealis argued that the claims of the patent lacked an inventive step over an ethylene copolymer sold under the trade name Engage 8400. An example in one of the prior art documents mentioned Engage 8400 as being suitable for the manufacture of solar cell modules. Engage 8400 was alleged to meet the requirements of claim 1 of the patent, except for the fact that it had an aluminium content of 4.4 ppm. Claim 1 of the patent required an aluminium content of 10-500 ppm. Borealis argued that this difference did not improve the properties of the copolymer, and thus that the claims lacked an inventive step.

One of Mitsui's arguments was that, according to an earlier EBoA decision G 1/92, a product can only be part of the prior art if it is available to the public, and that it can be analysed and reproduced. Their position was that Engage 8400 did not meet this requirement. It is this point that ultimately proved to be critical in G 1/23.

The appeal #

In the initial opposition hearing in November 2018 the arguments of Borealis were rejected and the patent was maintained as granted. This decision was appealed by Borealis in February 2019.

The EPO's Board of Appeal (BoA) noted that the inventive step of claim 1 depended upon whether Engage 8400 was part of the prior art. Mitsui said that reverse engineering Engage 8400 without knowledge of the catalysts and reaction conditions involved would require an extensive research programme which might not even succeed. As a consequence, Mitsui's position was that Engage 8400 could not be considered enabled and thus could not be prior art. The counter argument from Borealis was that, irrespective of whether Engage 8400 could be reproduced, the properties of this material (in particular those in claim 1 of the patent), as well as the product itself, were in the public domain. Borealis said that it would be unreasonable to ignore this information only because Engage 8400 could not be reproduced.

The BoA considered earlier decision G 1/92 in detail, and how the EPO's Boards of Appeal had utilised this decision. Given that G 1/92 had not been applied consistently in subsequent BoA decisions, the BoA referred questions to the EBoA, the EPO's highest decision-making body.

The referral #

The questions referred to the EBoA were as follows:

1) 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?

2) 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?

3) 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 composition and internal structure of the product be fully analysable and identically reproducible?"

The EBoA answered these questions as follows:

1) No, a product put on the market before the date of filing of a European patent application cannot 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 by the skilled person before that date.

2) Technical information about such a product which was made available to the public before the filing date forms part of the state of the art within the meaning of Article 54(2) EPC, irrespective of whether the skilled person could analyse and reproduce the product and its composition or internal structure before that date.

3) In view of the answers to questions 1 and 2, an answer is not required.

Conclusions #

The BoA that referred these questions will now need to apply them to the facts of the case. However, the expectation is that they will conclude that Engage 8400 is part of the prior art over which the claims of the patent will need to constitute an inventive step. It remains to be seen whether the patent as granted will meet this requirement, or whether it can be achieved by amending the claims.

This decision is particularly relevant for patent applicants working in the field of chemistry. This is because there are many commercial compositions whose composition is difficult to analyse, and whose manufacturing method is kept confidential, such that they cannot be reproduced. Decision G 1/23 has decided that such compositions cannot be ignored when novelty and inventive step are assessed. This potentially widens the field of citeable prior art for applicants for European patents in the field of chemistry. However, from the perspective of the manufacturers of such compositions, it does provide some reassurance that it will be difficult for third parties to obtain European patents covering those compositions. It will be interesting to see how G 1/23 is applied by the EPO's Boards of Appeal.

How we can help #

For businesses operating in fields like chemistry, life sciences, materials, and beyond, this ruling broadens the scope of what may be cited against a patent application - even when products cannot be reverse-engineered or reproduced.

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.

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