May 2025 Board of Appeal Decision T 1913/21
Strict rules of interpretation apply to the four categories of claim permitted by the EPO (product, method, apparatus, and use). It is usually clear from the claim wording which claim category is used to define an invention, however a recent decision from one Board of Appeal has confirmed that, in certain cases, claims initially appearing to be use claims are, in fact, to be interpreted as method claims.
It is generally accepted in the world of IP that all inventions fall into one of four categories: products, methods, apparatuses (i.e. products for carrying out specific processes), and uses. Thus, when drafting a new patent application, an important first step is to identify the nature of the invention the patent is intended to protect; the claims can then be worded accordingly.
It therefore follows that it is usually clear from the claim wording which of the four categories the claimed invention falls into, and thus what subject matter the claim should be understood to cover. For example, case law from the European Patent Office’s Boards of Appeal has held that a claim directed to a (non-medical) use of a product to achieve a specific effect is normally to be interpreted as including the effect as an essential functional feature of the claim. This means that, if the product as such is not new but it was not previously known to use (and there was no suggestion in the prior art to use) the product to achieve the effect, then the novel and inventive use of the product can be patented, even though the product as such cannot be.
However, a recent decision of one of the EPO’s Boards of Appeal has held that certain use claims are to be interpreted differently to the normal manner described above. Specifically, this Board of Appeal held that, if (i) the claimed use involves using one product to manufacture another product and (ii) the effect of the claimed use is attributable to a property of the manufactured product, rather than to the specific use of the first product, then the claim should be interpreted as being directed to a method of manufacturing the manufactured product, rather than to a use of the first product. This applies despite the claim being drafted as a use claim, rather than a method claim. In such a case, the effect attributable to a property of the manufactured product is not to be considered a functional feature of the claim, and thus novelty and inventive step are to be assessed based on the steps of the method alone
In more detail, the main claim in the case giving rise to the decision was directed to:
“Use of an inhibitor of cysteine degradation for reducing the formation of trisulfide bonds in proteins…”.
The claim recited that the use involved:
“… culturing cells expressing said proteins in the presence of an effective amount of the inhibitor of cysteine degradation, whereby trisulfide linkage formation in said proteins is reduced relative to cells cultured in medium without the inhibitor of cysteine degradation.”
The central issue was whether the claim should be interpreted as (i) a use claim directed to a use of a specific product (an inhibitor of cysteine degradation) in a certain way (culturing cells in its presence) to achieve an effect (reduced trisulfide bond formation) or (ii) a method claim directed to a method of manufacturing proteins having “reduced” trisulfide bonds.
Ultimately, the Board of Appeal held that the effect of reducing the formation of trisulfide bonds in proteins is inextricably linked to the production of proteins with “reduced” trisulfide bonds. In other words, the Board noted that the effect cannot be realised without such proteins being manufactured, and thus held the effect to be attributable to a property of the manufactured product. The Board thus interpreted the claim as being directed to a method of manufacturing proteins with “reduced” trisulfide bonds, despite the claim being written as a use claim. This meant the reduction of trisulfide bond formation was not considered to be a functional feature of the claim, therefore novelty and inventive step were assessed based on the physical steps of the method alone.
The prior art clearly disclosed methods of manufacturing proteins by culturing cells expressing proteins in the presence of an effective amount of a compound known to be an inhibitor of cysteine degradation. Thus, even though the prior art did not disclose that the inhibitor caused a “reduced” number of trisulfide bonds to form, the Board of Appeal held the claim to lack novelty.
Summary
This decision sends a clear message regarding the drafting of use and method claims in patent applications, and serves as a reminder to us all to ensure the appropriate claim format is used to protect each category of invention.
Specifically, use claims should be used to protect inventions associated with exploiting a product in a certain way to achieve an effect.
In contrast, if the invention lies in a novel and inventive method of manufacturing a product, then it is best to claim the method as such. One could also consider claiming the end product, provided that is itself novel and inventive, e.g. if there are advantageous properties associated therewith. However, in such cases, claiming the use of a product in the method of manufacture is not necessarily a good idea, as questions are likely to be asked about the correct interpretation of such a claim.
