In patent law, defining the scope of the prior art is a crucial step in assessing the validity of a patent right. A recent decision of the European Patent Office (EPO) has clarified that even a non-reproducible product may fall within the prior art, provided that it has been made available to the public.
Index:
- The concept of prior art in patent law
- The EPO decision
- Extension of the principle to inventive activity
- The specific case: polyethylene compositions
- Conclusions and practical implications
The concept of prior art in patent law
As is well known, for the purposes of patentability it is essential to determine what belongs to the prior art – that is, what is generally known or easily accessible – and what does not, since only subject matter that is new and non-obvious over the existing knowledge can be validly patented. On this issue, which is of considerable practical relevance, a recent decision of the European Patent Office has provided important clarification.
The EPO decision
The recent decision T 1044/23 of 24 September 2025 of the EPO Technical Board of Appeal clarified a particularly important point in this respect: a commercial product that is accessible to the public but not fully reproducible may nevertheless constitute “known prior art”, in line with what had already been established by the Enlarged Board of Appeal (decision G 1/23).
At first instance, the Opposition Division had excluded two commercial products from the prior art on the grounds that their method of production was not known and that they could not be reproduced exactly.
The Board of Appeal, however, completely overturned that decision, expressly referring to decision G 1/23, according to which a product placed on the market before the filing date of a patent application cannot be excluded from the prior art solely because it cannot be reproduced. It is sufficient that the product has been made available to the public, even in the absence of information enabling its manufacturing process to be replicated.
Extension of the principle to inventive activity
This significant decision goes beyond the issue of novelty and also affects the requirement of inventive step. The Board clarified that a non-reproducible product may nevertheless be selected, in the assessment of the validity of a patent right, as the closest prior art.
The specific case: polyethylene compositions
In the case at hand—which concerned a polyethylene composition for injection moulding—the products in question were well known for their mechanical properties and processability, making them a realistic starting point in the field of polyethylene compositions. However, although the exact manufacturing method of those products was not reproducible, this did not prevent them from being considered the closest prior art for the skilled person. It did, however, affect the subsequent stage of the analysis, namely the assessment of the obviousness of the claimed solution. The Board held that the skilled person would not have been able, without undue experimental effort, to arrive at the patented solution on the basis of what was known about those products—specifically, to modify the density of the composition while keeping the other parameters within the claimed ranges.
Conclusions and practical implications
This decision confirms the European approach: public availability of a product is the decisive factor for including it in the prior art, whereas its reproducibility, or lack thereof, is relevant to the assessment of the originality of a subsequently claimed subject matter.
This principle must be taken into account, as it has significant implications for patent strategies and future litigation.