Düsseldorf, July 9, 2025 – On 2 July 2025, the Enlarged Board of Appeal (EBA) of the European Patent Office (EPO) issued its long-awaited decision in case G 1/23 (“Solar Cell”)—a landmark decision that clarifies whether products that were available on the market before a patent’s filing date, but could not be fully analyzed or reproduced, qualify as prior art.
The EBA held that:
A product that was publicly available before the filing date of a European patent application cannot be excluded from the state of the art merely because its composition or internal structure could not be fully analysed or reproduced by the skilled person.
(Headnote 1)
This decision revises the longstanding double-requirement set out by the EBA in G 1/92 that a product must be analyzable and reproducible by the skilled person to form part of the prior art.
Background: From T 438/19 to G 1/23
The referral originated from Technical Board of Appeal 3.3.03 in case T 438/19. The underlying dispute concerned a patent for an encapsulating material for solar cells (EP 2626911), based on a complex polymer (“ENGAGE® 8400”) that was undisputedly commercially available before the priority date. Various pieces of technical documentation demonstrated certain properties of ENGAGE® 8400. However, as the parties agreed, the exact reproduction of a complex polymer is not a straightforward exercise (even if the final product is available for analysis) and the exact manufacturing method was not in the public domain. The patent proprietors (Mitsui Chemicals, Inc., and Mitsui Chemicals Tohcello, Inc.) argued that ENGAGE® 8400 had not been made available to the public within the meaning of Article 54(2) EPC with reference to the EBA decision G 1/92, because it could not be exactly reproduced. On the contrary, the opponent (Borealis AG) argued that ENGAGE® 8400 was novelty-destroying, irrespective to the extent to which it could be reproduced.
The EBA analyzed the different interpretations of the “reproducibility requirement” set out in G 1/92 and clarified that the term “reproduce” must be understood in a broader sense, namely as the ability of the skilled person to obtain and possess the physical product. This means that the “reproducibility requirement” is inherently fulfilled by a product that was commercially available.
With respect to published technical information on a product put on the market before the filing date of a European patent application, the EBA ruled that such information forms part of the state of the art, irrespective of whether the skilled person could analyze and reproduce the product and its composition or internal structure before that date.
The EBA concluded that all analyzable properties of the product put on the market became public alone by the possibility that they could have been analyzed, because the product was physically accessible.
What should not be overlooked, however, is that the EBA in reasons 76-79 of G 1/23 left open the question of whether there are legal limits to the extent of analysis a skilled person must perform to be able to derive information from a product on the market—specifically, whether only information and features of a product analyzable without undue burden becomes part of the state of the art.
The EBA acknowledged that this issue could arise in both real and hypothetical analyses but explicitly chose not to decide whether the concept of undue burden is a valid legal condition or where its threshold lies. It reasoned that the referred questions could be answered without addressing this issue, as they were based on the previous combined requirement of G 1/92 of analyzability and reproducibility. Since the particular case at hand did not seem to turn on whether an undue burden was required to analyze the product ENGAGE® 8400, the EBA omitted this criterion from its answers, but noted that this does not mean that the issue of the "analysis without undue burden" can never arise.
Impact on practice: Marketed Products Are Prior Art—Even Without a “Recipe”
“The decision has significant implications for patent practice, particularly in the fields of chemistry and life sciences”, says Dr. Natalie Kirchhofer, patent attorney and partner at Cohausz & Florack:
- Products made publicly available before a patent´s filing date are prior art as such, even if they are not fully analyzable or reproducible.
- At least all analyzable properties of such products are state of the art as well.
“Patent filing strategies must therefore now pay even closer attention to product launch and patent filing timing”, says Kirchhofer. The decision can be expected to not only impact EPO practice, but also invalidity proceedings before the UPC, and national courts (provided that they follow the EBA´s reasoning) and brings European law closer to a functional equivalent of the US “on-sale bar”.
Next to the chemistry and life sciences sector, G 1/23 can also be expected to affect the highly litigious fields of IT and communication technology. “G 1/23 will likely also apply to algorithms or hardware structures implemented in a semiconductor chip. Merely referring to the high complexity of reverse engineering of such products will thus likely not be sufficient to exclude them from the state of the art”, says Christoph Walke, patent attorney and partner at Cohausz & Florack.
“The recent G 1/23 ruling brings long-overdue clarity to a fundamental question of patent law”, says Dr. Arwed Burrichter patent attorney and partner at Cohausz & Florack. “It is an important step towards greater legal harmonization and clarity for patent owners and applicants across the European patent landscape. The Enlarged Board rightly rejected the idea that a marketed product must be fully enabled and reproducible to qualify as prior art if it was already commercially available. This decision strengthens legal certainty and aligns the EPO’s approach with practical realities in the chemical and materials sciences.” says Burrichter.
Picture credits: huntspy_AdobeStock.com
