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The Board of Appeal decision in T 2130/22 considered the inventive step of a pharmaceutical formulation in which the technical effect relied upon for inventive step was also a functional feature of the claim. The decision confirms that when a technical effect is specified as a functional feature in a claim, arguments regarding lack of demonstration of the effect across the whole scope of the claim will be considered by the EPO under the heading of sufficiency rather than that of inventive step. The claims in this case also highlights the need for patentees to be mindful of the potential enforceability of functional claim language.
Legal background: Functional features, sufficiency and inventive step
The assessment of inventive step at the EPO requires identification of the technical effect of the claimed invention over the closest prior art. When the technical effect is not specified in the claim, but rather relied upon for inventive step, there may be an issue if the effect is not demonstrated across the scope of the claim. However, when the technical effect is specified as a functional feature in the claim itself, the situation is different. As explained by the Enlarged Board of Appeal (EBA) in G 1/03, when an effect is part of the claim, objections regarding whether the effect is achieved across the scope of the claim should be considered under sufficiency of disclosure rather than inventive step (see G 1/03 point 2.5.2).
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In contrast to the EPO, UK courts have shown a tendency to consider the technical effect of an invention as a claimed feature regardless of whether it is explicitly included in the claim. This means that in the UK, evidence for both claimed and unclaimed technical effects relied on for inventive step may be considered under a unified “plausibility” analysis. This was highlighted in UK decisions such as Astellas v Teva [2023] EWHC 2571 (Pat) in which the court construed a claim as inherently requiring the technical effect relied on for inventive step, even though this effect was not explicitly claimed (IPKat).
Case Background: Stabilising submicron particles for ophthalmic delivery
The patent at issue in the case (EP 3470059, Bausch & Lomb) related to an ophthalmic suspension formulation of loteprednol etabonate (LE) (marketed as Lotemax). The formulation was indicated to be storage stable for at least one year whilst retaining submicron particles of the active ingredient. The Opposition Division maintained the patent in amended form, and the Opponent (Sandoz) appealed.
Claim 1 on appeal specified “an ophthalmic suspension comprising an ophthalmic active ingredient suspended in a formulation vehicle, wherein the […] formulation vehicle comprises […] hydroxypropylmethyl cellulose […] and wherein the suspension is storage stable for at least one year.” The key issues on appeal were sufficiency of disclosure and inventive step. The Opponent argued that the skilled person would not be able to prepare stable formulations across the scope of the claim using any grade and amount of hydroxypropylmethyl cellulose (HPMC). The Opponent also argued that the claimed formulation lacked inventive step over several prior art documents disclosing LE formulations.
Sufficiency of disclosure of functional features
The Board of Appeal found that the patent provided clear guidance on how to achieve the claimed functional feature of “storage stable for at least one year”. Particularly, the Board of Appeal found that the application as filed provided sufficient detailed information on how this could be achieved, given that the description gave specific concentration ranges for the critical components. The Board of Appeal noted that “the Table in paragraph [0043] gives the specific amounts of polycarbophil and HPMC, i.e. 0.1-0.5% by weight for both components, which are necessary to perform the claimed invention when LE is used as active agent” (r.2.2).
The Opponent argued that the skilled person would not be able to prepare stable formulations across the scope of the claim using any grade and amount of HPMC. However, the Board of Appeal found this argument unconvincing given the clear guidance in the description on suitable grades and concentrations of HPMC, as well as experimental data showing which formulations achieved the required stability.
The Board of Appeal thus found the functional feature of the formulation to be sufficiently disclosed given that the application as filed went beyond merely asserting the function was achieved, but instead provided specific working ranges for critical components, a technical explanation of the stabilisation mechanism, experimental data showing which formulations worked and which did not, and long-term stability data confirming the claimed effect.
Inventive step of functional features
The document considered by the Board of Appeal as the closest prior art for inventive step analysis disclosed a gel formulation of LE that was storage stable but did not have submicron particle size or contain HPMC. The technical problem was defined as the provision of a LE formulation having improved efficacy while maintaining storage stability.
The Board of Appeal found that none of the cited prior art documents provided a motivation to add HPMC to improve both the stability and efficacy of submicron LE particles in a polycarbophil formulation. The Board of Appeal particularly noted that “HPMC forms a more compact structure that can enhance the viscosity within the polycarbophil matrix, thereby reducing the particle movement and also inhibiting nucleation, thereby stabilising the small particles by reducing the Ostwald ripening effect” (r. 4.3.2).
The Board of Appeal thus set aside the Opposition Division’s decision and ordered that the patent be maintained according to the main request (filed as auxiliary request 1), which was identical to claim 1 as granted with some amendments to dependent claims. The case was remitted to the Opposition Division with the order to maintain the patent based on the main request, subject to any necessary adaptation of the description.
Final thoughts
In this case, the Board of Appeal rejected the Opponent’s argument that the technical effect had not been shown across the scope of the claim. Citing G 1/03, the Board of Appeal explained that since the storage stability was a functional feature of the claim, this objection was more appropriately considered under sufficiency rather than inventive step (r. 4.3.3). However, it is not clear to this Kat that assessment of the functional effect under inventive step would have led to a different outcome for the case overall. Regardless of whether the effect was considered as a feature of the claim, according to the principles established in the case law, the same test for the standard of evidence would apply (i.e. would a skilled person have substantiated doubts about the claimed/unclaimed effect). The issue of whether the feature in question should be considered under the heading of sufficiency or inventive step therefore appears a red-herring in this instance. In fact, consideration of the feature sole under inventive step may have helped the Patentee by reducing the disclosure requirement for the technical effect in the application as filed (per G 2/21).
It must also be noted that, despite the obvious advantages of functional claiming in terms of breadth of scope, care must still be taken with functional features. If a patent is to be successfully enforced, the claimed functional features of a product must also be easy to test for the purposes of successful enforcement against potential infringers. In order to enforce their patent, the patentee in this case would need to provide convincing evidence that the alleged infringing formulations have the claimed feature of being “storage stable for at least one year”. This feature might be rather time-consuming feature to test!
Further reading
- Construing claims to include technical effects mentioned in the description (T 1924/20) (April 2023)
- Broad functional claiming at the EPO (T 0835/21) (Sep 2023)
- Benefits and pitfalls of functional patent claims (and why the UK is out of step with the EPO on claim construction): Astellas v Teva [2023] EWHC 2571 (Pat) (Nov 2023)
- The criteria for the novelty and inventive step of pharmaceutical selection inventions (T 1356/21) (Dec 2023)
- Stretching the cheese: Contradictory evidence for a purported technical effect relied on for inventive step (T 0629/22) (May 2024)
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