Board of Appeal proposes a substantially broader definition of "substance or composition" in second medical use claiming (T 1252/20)

The recent Board of Appeal decision in T 1252/20 proposed a substantially broader category of products permissible for second medical use claiming. The Board of Appeal disagreed with the previous approach in the case law of restricting second medical use claiming to products having a chemical mode of action. For the Board of Appeal in T 1252/20, the category of "substance or composition" should include any product that may be defined by its chemical composition, regardless of the mode of action of the product in the body. 

Legal Background: Substance or device, a distinction without a difference? 

At the EPO, methods of treatment are not patentable. However, it is possible to patent "substances or compositions for use" in a method of treatment, surgery or diagnosis. Substances and compositions are thereby singled out as a special category of product. A known product for a new non-medical use cannot be patented, as a claim for a product for a non-medical use would be construed as a product "suitable for" the claimed use. If the product is already known, then the claim is thus anticipated by the product itself. By contrast, a second medical use claim is construed as including the functional effect of the claimed use. The new medical use of a known substance or composition is therefore considered novel (G 02/88Articles 54(4) and (5) EPC). Importantly, this provision does not apply to any product, but only to products falling under the definition of "substance or composition". 

Substances or devices?

What then is a "substance or composition"? The EPC does not define "substance or composition". According to G 05/83, a "substance or composition" in Article 54 EPC should be understood to mean an "active agent" providing a therapeutic effect in a medicament. In order to establish whether a product is a substance or composition it is therefore necessary to determine the means by which the therapeutic effect is achieved and whether the product in question interacts biologically and/or chemically with the body. According to more recent case law, only products that interact chemically with the body are "substances or compositions" (T 1758/15, IPKat). Particularly, according to the EPO Guidelines for Examination (which follow T 1758/15IPKat), if the therapeutic effect of a product is based exclusively on the "macroscopic 3D-structure formed by a composition once inside the body", the product should be considered a device, and thus not a "substance or composition" according to Articles 54(4) and (5) EPC (G-VI-7.1).

Defining a substance or composition by its mode of action

T 1252/20 related to the Examining Division (ED) decision to refuse EP 2919826. Claim 1 of the applicant's main request related to "a composition for use in reducing or eliminating cancerous cells" by blocking the blood supply to the tumour. The claim defined the composition as a peptide forming a hydrogel. The peptide was defined by it's specific amino acid sequence. The ED was of the view that the peptide did not constitute a "substance or composition" according to Articles 54(4) and (5) EPC. Referring to T 1758/15 and the Guidelines the ED found that the peptide hydrogel had a physical mode of action and was thus a device and not a substance or composition. As such, the claim was construed as not including the therapeutic effect as a claimed feature, and thus found to lack novelty given that the peptide was already known. 

On appeal, the Board of Appeal noted the case law that a substance or composition under Articles 54(4) and (5) EPC has to be "the active agent or ingredient" for the particular specific medical use, and that a substance or composition must have a "chemical" mode of action T 1758/15  (IPKat). On appeal, the applicant argued that the therapeutic effect of the peptide hydrogel was due to its chemical properties. However, in a departure from the existing case law, the Board of Appeal was convinced that the peptide hydrogel should be considered a "substance or composition" for more fundamental reasons. 

Board of Appeal takes a fundamentally different approach to the definition of "substance or composition" Articles 54(4) and (5) EPC

Contrary to the established case law, the Board of Appeal in T 1252/20 found that there was no legal basis for defining a medicinal product as a device as opposed to a "substance or composition" solely on the basis of its mode of action (i.e. chemical versus physical) (r. 9). The Board of Appeal particularly did not consider G 05/83 provided any legal basis for using the mode of action of a product as the relevant criterion for judging whether the product is a substance or composition: "if the substance itself is the key element in the therapeutic, surgical or diagnostic method the ratio decidendi of G 05/83 is applicable to such substances, irrespective of their mode of action"  (r. 9.2.2),

The Board of Appeal further found that the use of the mode of action as the defining criterion for whether a product is a "substance or composition" was problematic for several other reasons:

  1. First the Board of Appeal noted that the material acting inside the body may not be the same as the product to which a patent claim is directed. In the case in question, the claim was to a peptide which formed a hydrogel once inside the body.  Second medical use claims are generally directed to the administered product (this being the commercially important embodiment). For the Board of Appeal it did not make sense to evaluate the mode of action of the administered product, as the product could change following administration. 
  2. Second, the Board of Appeal noted that the mechanism of action of a product may not be understood in detail. Assumptions about the mechanism of action of a product may also later turn out to be wrong. In particular, "[e]ven classical medicaments may trigger a therapeutic physiological reaction without the mechanism for it being fully understood." In the Board of Appeal's view, Articles 54(4) and (5) EPC do not require that the mechanism of action of a substance or composition to be understood. 
  3. Next the Board of Appeal observed that a product may behave in different ways according to its mode of administration. In one context a product may interact physically, whilst in another context it may interact chemically with receptors or other biological structures in the body. In the words of the Board of Appeal "[i]t appears odd to classify the very same material as a 'substance or composition' or not depending on extrinsic factors not related to the material itself, but to its way of administration."
  4. Finally, for the Board of Appeal, restriction of the definition of "substance or composition" by way of mode of action "does not achieve the legislative purpose, namely to provide at least a complementary form of protection for an otherwise recognisably useful invention in a field where, despite its excluded nature, technical development is otherwise highly desirable and beneficial and therefore patent protection should also be available for such development".
So how is one to distinguish between a device and a "substance of composition" if not by mode of action? In the case in question, the Board of Appeal found the lack of any "device-like features" of the product, e.g. shape, as clearly demonstrating that the product was not a device (7.2). For the Board of Appeal in T 1252/20 therefore, a product may be considered a "substance or composition" in a second medical use claim if the claim a) defines the chemical composition of the product and/or a) does not define device-like features of the product (e.g. shape). The Board of Appeal further found that these criteria were satisfied with the respect to the claim in question. The peptide was defined by its chemical composition, in the form of its amino acid sequence, and was a shapeless liquid without any device-like features. Second medical use claiming for the product was therefore permissible, and the claim was found novel in view of the prior art. The case was then remitted back to the ED for further prosecution. 

In T 1252/20 therefore, the Board of Appeal was of the view that the category of products that may be considered "substances and compositions" Articles 54(4) and (5) EPC is substantially broader than that defined by the previous case law. However, the Board of Appeal was clear that this did not open the door for patentability of second medical uses of products that are clearly devices (r. 11). For the Board of Appeal in T 1252/20, products such as pacemakers and scalpels remain "devices", for which second medical use claiming should not be available. 

Final thoughts

The Board of Appeal decision in T 1252/20 is a welcome injection of common sense into the case law on second medical use inventions. As commented by the Kat back in 2018, the case law on "mode of action" is difficult to make sense of (IPKat). The previous case law on the definition of a product as a "substance or composition" attempted to draw a distinction without a difference between medical products based on mode of action (IPKat). As outlined by the Board of Appeal in T 1252/20, this approach is fraught with difficulty. The historical approach also failed to take into account advancements in the field, specifically the increasing incorporation of biological and chemical elements into medical devices. The new definition of "substance and composition" proposed by the Board of Appeal in T 1252/20 seeks to define a product more in terms of the product's own characteristics, as opposed to the interactions it may have with the body. 

However, this Kat is not sure that the dividing line between what is and what is not a device is yet entirely clear. Particularly problematic is what it means for the "chemical composition" of a product to be defined (by the very nature of the universe, do not all products have a definable chemical composition?). This approach could also lead to some creative claim drafting. The decision in T 1252/20 removes some of the difficulty in defining a device and broadens the category of products that may be the subject of second medical use claims. However, whether a product is a substance or a device will still require a case-by-case assessment. 

Further reading

Board of Appeal proposes a substantially broader definition of "substance or composition" in second medical use claiming (T 1252/20) Board of Appeal proposes a substantially broader definition of "substance or composition" in second medical use claiming (T 1252/20) Reviewed by Rose Hughes on Thursday, February 15, 2024 Rating: 5


  1. I have been commenting the present decision in a different blog.

    Although I can understand the intention of the board, I cannot share its views on G 5/83.

    G 5/83 was there to introduce Swiss-type claims which had for aim at protecting, not the use, but the manufacture of substances and compositions used in a further therapeutic application. Through Art 54(4 and 5), Swiss-type claims have become obsolete and are now even forbidden.

    Any substance or composition being a “substance or composition” in the meaning of Art 53(c) has the following properties:
    – firstly, that they disappear when used and
    – secondly, they are eliminated by mechanisms proper to the body.

    This is the case for substances having a direct therapeutic effect, but also for substances used for instance for enhancing contrast in medial imaging methods so as to come to a diagnostic.

    Whatever happens, those substances or compositions cannot be reused and are eliminated by the body itself.

    I am however not convinced that the hydrogel of the invention underlying T 1252/20 will disappear by mechanisms proper to the human body.

    The case law discussed in T 1252/20 with T 264/17 can be considered divergent with respect to other decisions like T 1758/15, T 2136/15 and T 1345/18.

    It could thus be useful if a corresponding question would be referred to the EBA.

  2. "However, this Kat is not sure that the dividing line between what is and what is not a device is yet entirely clear."

    The Kat is not alone. Regulatory authorities also struggle with this - see the guidance on so-called "borderline products" e.g. at

    and at

    This can have implications not only for patentability but also for SPC protection, given that borderline products might be classified as a medicinal product (and thus, in principle, SPC eligible) in one country but as a medical device (and thus not SPC eligible) in another country.

    The CJEU confirmed in Boston Scientific C‑527/17 that products authorised as medical devices are not eligible for SPC protection even though the authorisation process can include the same or similar evaluation of safety, efficacy etc. of chemical substances incorporated into those devices which would take place under the medicinal products authorisation route.

    This means that a quirk of the regulatory arrangements for borderline products can cause variation in SPC eligibility for one and the same product from one country to the next.

    1. I think that we should not confuse obtaining a SPC with patentability criteria.

      The prerequisite for regulatory approval. like a SPC, be it for a substance or composition or for a device, is to obtain a patent. The conditions for obtaining a patent have nothing to do with regulatory approval and obtention of a SPC.

      In a recent decision, I could alas not find quickly, I remember a board stating that in order to demonstrate the efficiency/plausibility of a substance it was not necessary to bring a statistically relevant number of tests, like those requested for regulatory approval

    2. I am not arguing that the conditions for obtaining regulatory approval or an SPC are the same as the prerequisites for patentability. I am simply observing that both the EPO and regulatory authorities find it difficult, in some cases, to draw the line between what is a "device" and what is a "medicinal product" or a "composition". Given this difficulty, it is quite possible that where the line is drawn will differ from a patentability perspective and from a regulatory perspective.

      This is a practical illustration of the difficulty of constructing a clear definition of what is and what is not in each category, and some of the consequences of that difficulty.

    3. At a glance, I can agree with you that it can be difficult to distinguish what is a device and a substance or composition in the meaning of Art 53(c).

      In my blog, folowing numerous comments, I have come to the following conclusion: when looking at the sprit and scope of G 5/83, and at the subsequent case law, a substance or composition in the meaning of Art 53(c) has the following properties:
      - it cannot be reused
      - it is chemically transformed by the body, resorbed or eliminated from the body in one or the other way.

      It might look too simple, but I think that it can help to make a distinction as a device can in principle be reused and does not disappear from the body, besides some rare exceptions, e.g. self disolving stitches or stents. Even the latter enter the body in form of a device.

      When looking at the hydrogel in T 1252/20, it is difficult to say that it will be resorbed by the body, but I accept to be proved wrong as I am not a chemist.

    4. I'm not sure it's that easy to distinguish to be honest - it depends on a host of factors, including where the device/composition would be placed. For example, an ink used for tattooing can't be reused but is neither transformed, resorbed or eliminated from the body because it's implanted in a layer of the skin that prevents that. Think also about hormonal contraceptive implants that can be considered to be a device but also possess the features of a composition. There are also vaccine adjuvants that have no real effect in the body alone but when combined with an antigen, enhance the immune response to the antigen. I think attorneys need to have a proactive strategy in mind and consider all the bases when drafting and prosecuting - include suitable language and arguments where your invention bridges device and composition.

  3. In the past I have written and filed an application on the use of (a specific form of) electric stimulation for providing therapeutic effects. Although the application was withdrawn because the applicant lost interest, it would have been interesting to have the discussion on a first or second medical use in respect of this technology. I would guess that on basis of what the board now has said in T 1252/20 and on basis of the comments of Daniele Thomas, this claim could have been successful.
    What would you think: would nowadays a claim such as 'Electro-convulsive shocks for the therapy of mental disorders' be patentable (of course when novel and inventive)?

  4. A substance is defined by its chemical composition (small molecule, macrocycle, peptied, DNA molecue, RNA molecule, polymer) either directly or by the eprocess for its manufacture. A composition is a combination of one or more chemical substances. I have no doubt that the hydrogel-forming peptide is clearly a composition, irrespective of its mechanism of action. I'm sure I am not alone in believing this to be the case.

    "A composition that is an alloy of iron and carbon having structure x with dimensions y" is clearly a device even though it is defined by its molecular composition, because its secondary structure defines shape and not an interaction between the molecules. Contrast this with protein complexes, which are not devices.

    Lacking the ability to re-use or elimination by the body are artificial definitions that show no understanding of the underlying science. Drugs that are eliminated unmetabolised may be re-used in a technical, if not regulatory, sense. Swallowed cameras are eliminated, but are clearly devices.

    "The use of a camera capsule to photograph the intestine" is not a method of treatment so the use claim is allowable. "The use of a peptide forming polymer to treat cancer" is a method of treatment so no use claim is allowable.

  5. 'Electro-convulsive shocks for the therapy of mental disorders' is clearly a method of treatment, so not patentable. The device used for producing the shocks is clearly a device. Define it as a composition using the molecular structure of its components without referring to structure/shape, and I'll give you a patent myself.


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