G 1/23: EPO Enlarged Board of Appeal shines a light on non-reproducible prior art

The European Patent Office’s Enlarged Board of Appeal has issued its long-anticipated decision in G 1/23, a referral that raised fundamental questions about whether commercially available products, when not fully analysable or reproducible, can be treated as part of the state of the art under Article 54(2) EPC.

As expected in view of both the preliminary opinion and the oral proceedings held earlier this year, the Enlarged Board has clarified that reproducibility is not a legal requirement for prior art status under the EPC.This marks a significant development in EPO case law with broad practical implications.

Background to the referral

The referral originated in decision T 438/19, which concerned European Patent No. 2626911 relating to a polymer encapsulant material for solar cells. At issue was a commercially available material known as ENGAGE^® 8400, which had been put on the market before the filing date and described in technical literature, but could not be exactly reproduced by a skilled person because its manufacturing method was not publicly disclosed.

The referring Board raised doubts as to whether the criteria set out in G 1/92, which required that a product must be both analysable and reproducible without undue burden, should still govern what constitutes the state of the art. It therefore referred three questions to the Enlarged Board to clarify the correct interpretation of Article 54(2) EPC.

Decision

The Enlarged Board has now answered the referred questions as follows:

Question 1: A product put on the market before the filing date cannot be excluded from the state of the art merely because it cannot be analysed and reproduced without undue burden.

Question 2: Technical information about such a product (e.g. in brochures or literature) is also part of the state of the art, regardless of reproducibility.

Question 3: No answer was given, as the Enlarged Board found the underlying reproducibility requirement to be unfounded, rendering the third question moot.

The Board emphasised that what matters under Article 54(2) EPC is whether the product or information was factually accessible to the public, not whether it was fully analysable or reproducible by the skilled person.

The Board concluded that interpreting G 1/92 as imposing a reproducibility requirement leads to legally untenable outcomes and lacks support under the EPC, particularly when applied consistently across technologies. Importantly, the Board interpreted “reproduce” in the referred questions as meaning reproduction “by a different route”, i.e. manufacturing from different starting materials rather than simply obtaining the product from the market. Rather than applying enablement requirements, the Board held that public availability, defined as factual accessibility, not theoretical reproducibility, determines whether a product is part of the state of the art. The Board found that both prevailing interpretations of G 1/92 regarding reproducibility, that either the whole product or only its composition should be excluded if non-reproducible, led to “manifestly absurd” consequences and thus could not be maintained. It was noted that strict reproducibility requirements would logically render virtually all materials unavailable as prior art, since all products ultimately depend on non-reproducible starting materials.

Impact of the decision

The decision has several important consequences for patent practice before the EPO:

• Commercial products are prior art as soon as they are marketed, with no second chance to patent them. The Board confirmed that a product becomes part of the state of the art under Article 54(2) EPC the moment it is made publicly available, even if its internal structure or manufacturing process cannot be analysed or reproduced. This brings European law closer in practical effect to the US “on-sale bar”, as it prevents later patenting of products that have already been commercially available, even by the original producer.
• All publicly derivable technical information is relevant. Features that can be identified through standard analysis of a marketed product, or are disclosed in brochures, datasheets, or other technical materials, form part of the state of the art, regardless of whether the product itself is reproducible.
• Early filing is essential. The decision reinforces the importance of securing patent protection before making a product publicly available, including by sale or disclosure. This is particularly critical in fields like polymers, pharmaceuticals, and advanced materials, where products may not be easily reverse engineered yet still risk entering the public domain through sale or public disclosure.
• Novelty and inventive step must be assessed differently. While non-reproducible products cannot be excluded from prior art status under Article 54(2) EPC, the Board clarified that the extent to which such products contribute to the assessment of inventive step depends on what technical teaching the skilled person can actually derive from them. This assessment is context-dependent and influenced by the skilled person’s general knowledge, the analysable properties of the product, and practical limitations.

The Board noted that since reproducibility is not required, it was unnecessary to further interpret the “analysis without undue burden” requirement condition from G 1/92, leaving this open for future clarification.

Looking ahead

The Enlarged Board’s decision in G 1/23 clarifies that the legal definition of the state of the art under the EPC is based on factual public availability, not on theoretical reproducibility, aligning it more closely with commercial and technical realities. It marks a departure from the restrictive interpretation of G 1/92 and clarifies that availability to the public is a question of factual access, not of enablement.

This outcome will be welcomed by opponents seeking to rely on commercial products as prior art, but requires greater caution from patent proprietors when launching products prior to filing.

If you would like to discuss the implications of G 1/23 for your portfolio or strategy, please get in touch with us: gje@gje.com.