Patenting materials in medical devices at the EPO

Materials are important. They are the stuff that new things can be made of. Whether that’s a functionally coated medical implant, a particularly clear and comfortable ocular device or as part of a system for filtering blood, materials underpin many inventions in the healthcare sector. Within the innovation-driven medical device industry, new materials can significantly enhance device performance, patient safety, and treatment outcomes, leading to competitive advantages. Protecting materials-related inventions is therefore of high importance.

There are a number of requirements for a patent to be granted, not least that the invention to be protected must be novel and inventive. Assuming those hurdles have been met, consideration needs to be given as to how to best claim the invention. Claims determine the extent of protection conferred by the patent and must be clear and concise and supported by the description. They need to adequately define the material(s) that forms the basis of the technology. A patent application must also provide sufficient teaching to enable the skilled person to perform the invention (the invention must be sufficiently disclosed). A thought should also be given to the types of claims in the application – obvious contenders are product/apparatus claims and process (manufacture) claims, but may there also be scope for a method of use claim?

This article will discuss factors to consider when drafting an application protecting materials used in medical devices, with a few examples to highlight some specific challenges.

Claim language

Claims might include functional language, provided that a person skilled in the art would have no difficulty in providing some means of performing the function without exercising inventive skill. That is, they must be able to provide one or more materials that achieve such a function. The claim may specify that a medical device includes a surface layer “for the prevention of microbe growth”, where the skilled person understands this could broadly cover coatings containing, for example, antimicrobial materials such as zinc pyrithione, silver, isothiazolinone treatments, and quaternary ammonium compounds. Specifying the exact materials, or even the class of materials, might be unduly limiting on the scope of protection, whereas functional language can provide broader coverage and can be harder for potential infringers to design around.

However, extremely broad-brush functional language or attempts to define the invention by a result to be achieved are generally not allowed, in particular if they only amount to claiming the technical problem underlying the application. An independent claim should indicate all the essential features of the object of the invention in order to comply with the requirements of Article 84 EPC (G 2/88 and G 1/04).  The extent of the monopoly conferred by a patent, as defined in the claims, must correspond to the technical contribution to the art. If the essential features necessary to achieve the result are not claimed, then third parties are unable to assess whether they are infringing the patent – the claim is unclear. Nevertheless, claims encompassing a result to be achieved may be allowed in certain circumstances[1]. For example, a claim directed to an “effective amount” of an antimicrobial agent “sufficient to substantially inhibit microbial growth”, may be allowed if further defining the amount of the agent would unduly restrict the scope of the claim and the skilled person would be able to directly and positively verify the degree of inhibition of microbial growth.

Alongside functional language, claims typically include structural limitations, defining characteristics that are critical to the material’s functionality or properties. Devices encompassing certain materials may benefit from the specific properties of that material, leading to improved performance and innovation. The mechanisms underpinning that performance might be better understood via advanced characterisation techniques, and parameters derived from those techniques can be used to define the invention. Whilst parameters might give the illusion of precision when compared to functional language, a parameter with an unclear or missing measurement method can be open to different interpretations, making it difficult for a third party to determine whether they are infringing the claim. European Patent Office (EPO) Guidelines require that a measurement method for a parameter is included in the claim itself[2], unless it can be convincingly shown that[3]:

•    the measurement method to be employed belongs to the skilled person’s common general knowledge (e.g., because there is only one method, or because a particular method is commonly used); or

•    all the measurement methodologies known in the relevant technical field for determining this parameter yield the same result within the appropriate limit of measurement accuracy.

Thus, for any parameter that might be measured in different ways, giving rise to different results, caution must be exercised when using the parameter to define the material.

Examiners frequently raise clarity objections to parameters such as “viscosity”, “glass transition temperature”, “molecular weight”, “porosity” and “particle size”, as well as more “unusual parameters” (which might make a comparison with the prior art difficult). Since clarity is not a ground for opposition, opponents typically attempt to show that the unclear term makes the claim so broad as to be anticipated by the prior art, or that the parameter renders the claim insufficient due to an absence of detailed information as to how it is measured.

The description

Sufficiency at the EPO requires that there is enough information in the specification to allow the person skilled in the art, using common general knowledge, to perform the invention over the whole area claimed without undue burden and without needing inventive skill. That is, regardless of whether or not the claim defines the material using parameters, the best practice would be to include a detailed description of the material’s composition, structure, and manufacturing process. Details such as the chemical, physical, mechanical or electrical properties that are critical to the material’s functionality are also important, as well as the conditions that are essential for performance and/or manufacture. Examples can help to demonstrate the features essential for carrying out the invention such that it is apparent to the skilled person how to put the invention into practice[4].

As discussed above, if the measurement method is part of the skilled person’s common general knowledge, it might be possible to omit the technique from the description. For example, in certain subject areas, such as powder technology, the measurement technique for an average pore size or diameter of particles may be extremely common such that the skilled person could put a suitable method into practice. However, even for very well-known parameters, there are limits to the extent that common general knowledge can be relied upon to overcome any deficiencies in the disclosure of the measuring method. A level of uncertainty in the limits of protection might affect the clarity of the claim, but a greater level of uncertainty might make it impossible for the skilled person to carry out the invention and thus compromise the sufficiency of the disclosure.

Effective drafting of the description not only ensures the requirements of sufficiency of disclosure are met, but also that there is a sound basis for future amendment as well as an adequate description of key features to minimise the chance for interpretation disputes in opposition and appeal proceedings. As to the latter, there is a degree of divergence in the case law over the extent to which the description and drawings should be used to interpret claims and a decision on this is being referred to the Enlarged Board of Appeal. The referring Board in T 439/22 stated that “a narrow interpretation of the claim language ignoring a definition giving [sic] in the description would also conflict with a broader interpretation by national courts or the UPC when having to deal with the granted claim later during the live [sic] of the parent”[5]. Given the current different approaches to claim interpretation by EPO Boards, careful thought should be given to the detailed description and how it may be used to interpret the claims (particularly in view of its use by national courts as an explanatory aid for the interpretation of the claims).

Claim types

In addition to claims seeking protection for the new product/material and method of manufacture, claims directed to the method of using the product might be included. If a medical device is applied in a novel and inventive way, it may be possible to patent the new method of using the device alongside patenting any enhancements or modifications of the device itself. Use claims provide an additional layer of protection for novel medical devices and can offer valuable protection when a new use of a known product has been identified. Use claims might cover both non-therapeutic methods as well as therapeutic methods, although care must be taken for medical device-related inventions as Article 53(c) EPC excludes methods for treatment of the human or animal body by therapy or surgery from being patented. The exclusion does not, however, apply to products, in particular substances or compositions, for use in said methods.

The legal framework of the EPO differentiates between chemical/pharmaceutical inventions and medical devices, but the dividing line between what is a substance or composition and what is a device is not entirely clear. In T 2003/08, the Board considered that the “substance” or “composition” must achieve the medical effect and that the terms “substance” or “composition” referred at least to products which were chemical entities or compositions of chemical entities. According to T 1758/15, products that have a chemical “mode of action” are “substances or compositions”. However, the recent Board of Appeal decision in T 1252/20 proposed to define the product in terms of its own characteristics instead of the interactions it may have with the body: a “substance or composition” should include any product that may be defined by its chemical composition, regardless of the mechanism of action of the product in the body.

Following T 1252/20, a broader category of products may be permissible as the subject of second medical use claims. For medical devices comprising novel materials, creative claim drafting might enable protection in the form of a medical use claim directed to the material defined by its chemical composition (avoiding the use of device-like features such as shape or pore-size). Whether a product is a substance or composition, or a medical device will still require a case-by-case assessment. Therefore, it may be prudent to include use claims for products that might previously have been considered medical devices, even if there is a question over whether the material used is a “substance or composition”. The description should include details of the product delivery and its mode of action by chemical means in order to follow the reasoning in this decision, particularly since this area of law remains unclear.

The following case studies look at some examples of challenges that can be faced when claiming materials in medical devices.

Case Study 1 – supporting experimental data/evidence for sufficiency of disclosure

Chemical formulae are infrequently used in the medical device sector, with a preference given to more functional language which may allow for a broader claim.  Nevertheless, a material which may be defined by its chemical formula, can provide a simple and elegant claim:

“A medical implant comprising a biodegradable magnesium-based alloy with a surface layer comprising a magnesium carbonate, characterized in that, the magnesium carbonate has the formula Mg₂[(OH)₂(CO₃)] · 3 H₂O.”

The specification provided a detailed description of the experimental conditions required to achieve a magnesium carbonate coating on the magnesium-based medical implant. The specification indicated that different types of magnesium carbonates could form depending on the atmospheric conditions, and included an example with the conditions required to achieve the specific formula claimed (Mg₂[(OH)₂(CO₃)] · 3 H₂O). The example allegedly confirmed the presence of the specific magnesium carbonate via an infrared spectrum identifying the coating material.

However, during an opposition, prior art was found to demonstrate that the depicted spectrum did not in fact correlate with that of the claimed chemical formula. The Opposition Division considered that the spectrum did not allow the conclusion that the claimed material was actually obtained in the example, raising the question of sufficiency of disclosure, since the skilled person would be faced with having to perform more experiments to determine how to obtain the claimed formula, a “research program”.

It is thus key, that the specification provides sufficient experimental details required to achieve the claimed chemical formula defining the material and any examples and/or data support this. Patent attorneys and inventors must work closely together to ensure that any examples contain all the conditions needed to achieve the claimed product, and that any data presented in the application confirms the materials are achieved.

Case Study 2 – details and definitions for functional features

Functional language is frequently used to define a material, but difficulties can arise when insufficiency and/or lack of clarity objections are raised, and there are a lack of amendment options in the description.

Packaging material for an ophthalmic lens was defined as absorbing less than a certain amount of the therapeutic agent comprised within the lens it was intended to package:

A blister pack for packaging an ophthalmic lens comprising therapeutic agents, wherein said blister pack comprises a polymeric material that absorbs less than 10% of said therapeutic agents.

Experimental data was provided in the application testing the percentage absorption of a solution of a specific therapeutic agent by specific polymeric materials, defined by their tradenames[6]. The data showed that certain polymeric materials were not suitable. The Examining Division objected that the invention was not sufficiently disclosed across the scope of the claim since the experimental data could not be deemed representative of any therapeutic agent or any class/group of polymeric materials. The Division also objected that the conditions under which absorption of the therapeutic agent was tested, such as concentration of the therapeutic agent, duration of exposure to the solution/material and test temperature, were not specified and no standard test was referred to. Since the test method affected the technical effect underlying the present invention, the absorption of the agent, this further contributed to lack of sufficiency of disclosure. It was objected that the person skilled in the art, using their common general knowledge, was unable to perform the invention over the whole area claimed without undue burden and without needing inventive skill.

Notwithstanding the challenges faced as a result of the lack of experimental details, the application also did not provide basis to define polymeric materials more generally. The definition provided for the general class/group of polymers relied on the glass transition temperature – a parameter, which was not further defined, and no measurement method was supplied.

The functional feature was in the claim as filed and could not be removed without contravening Article 123(2) EPC. However, there was no basis for an amendment to clearly define the class or group of polymeric materials and the application did not contain sufficient detail to enable the skilled person to measure the therapeutic agent absorption. As such, these problems were terminal for the application.

The inclusion of progressive amendment options in the description (e.g., general polymeric material, general class/group of polymers, specific polymers, tradenames) as well as complete details of experimental conditions is therefore important.

Case Study 3 – medical use claims and consideration as to the “substance or composition”

An invention may reside in a new filter apparatus comprising a material for removing a chemotherapeutic agent from blood. Whilst claims directed to a method of using the filter apparatus (below) may be allowable in some jurisdictions, such as the US, they are not in a format permitted at the EPO.

“A method of treating a subject with cancer of the liver comprising:

isolating blood flow out of a vein,

administering a chemotherapeutic agent,

collecting blood laden with the chemotherapeutic agent, and

filtering the blood laden with the chemotherapeutic agent with a filter apparatus comprising an extraction medium comprising activated carbon.”

These types of claims need reformulation before the EPO. Use of the apparatus in filtering blood encompasses therapeutic and surgical aspects, falling under the exclusion of Article 53(c) EPC. One claim format might focus on claiming the chemotherapeutic agent, a “substance or composition”, in a format corresponding to Article 54(5) EPC:

“A chemotherapeutic agent for use in a method of treating a subject with cancer of the liver, said method comprising:

isolating blood flow out of a vein,

administering said chemotherapeutic agent,

collecting blood laden with the chemotherapeutic agent, and

filtering the blood laden with the chemotherapeutic agent with a filter apparatus comprising an extraction medium comprising activated carbon.”

The Examining Division questioned whether the use of the chemotherapeutic agent was novel over the prior art. The Division considered that the difference over the prior art resided primarily in the new filter apparatus, and the use of the chemotherapeutic agent (in treating cancer of the liver) was not necessarily modified or adapted in connection with the subsequent filtering of the blood. As such, the use of the chemotherapeutic agent as claimed was deemed not to be novel or inventive over the prior art: it involved neither a new compound, nor a new therapeutic agent, nor a new treatment regimen[7].

It can be difficult in these circumstances to reformulate such a use claim to capture the medical device. Alternative claim “reformulations” might focus on a claim to the specific use of the new material, the activated carbon:

“Activated carbon for use in a method of treating a subject, said method comprising:

isolating blood flow out of a vein,

administering a chemotherapeutic agent,

collecting blood laden with the chemotherapeutic agent, and

filtering the blood laden with the chemotherapeutic agent with a filter apparatus comprising an extraction medium comprising the activated carbon.”

A question arises as to whether the activated carbon is a “substance or composition” within the meaning of Article 54(5) EPC. It may be possible to completely define the activated carbon in terms of its chemical composition, following the decision in T 1252/20, or even assert that the “mode of action” is a chemical interaction (in line with T 1758/15) between the activated carbon and the chemotherapeutic agent so as to remove cancer cells from the blood of patients. However, if the invention lies in device-like features of the activated carbon, such as shape or pore-size, then it is unlikely that this claim format will meet the requirement for second medical use claims to be patentable.

Key takeaways

A balance has to be struck between providing an adequate and often detailed definition of a material (for clarity and novelty purposes), and retaining a breadth of claim that is harder for potential infringers to design around. For materials-related inventions, this often involves the use of functional claim language alongside structural language, including parameters, to define the material/device. The functional language should relate to clear and easy to measure functional properties so that any alleged infringement can be proven.

Together with ensuring that the patent application provides sufficient disclosure of the invention, the inclusion of detailed definitions, measurement methods and enabling examples in the description can provide options for incremental amendments. This not only gives reassurance at the drafting stage and is critical for obtaining a granted patent, but also provides a patent which can be enforced and defended against challenges.

A patent attorney who specialises in the field of materials science can be invaluable in obtaining a clear, enabled and robust patent capturing inventions relating to materials used in the healthcare sector.

[1] If the invention can only be defined in terms of a result to be achieved, or if defining more precisely would unduly restrict the scope of protection and if the result can be directly and positively verified by tests or procedures adequately specified in the description or known to the skilled person and which do not require undue experimentation (T 68/85).

[2] If the description of the measurement method is so long that inclusion makes the claim unclear or difficult to understand then a reference to the description can be included in the claim instead.

[3] The applicant might submit an expert declaration or experimental data to prove one of these exceptions applies.

[4] A single example may suffice, but where the claims cover a broad field, the application is not usually regarded as satisfying the requirements of Article 83 unless the description gives a number of examples or describes alternative embodiments or variations extending over the area protected by the claims. (Guidelines Part F-III, 1)

[5] Point 6 of the communication of 5^th December 2023.

[6] Under the EPO Guidelines Part F-IV, 4.8, the use of trademarks in the claims is not allowed as it does not guarantee that the product referred to is not modified while maintaining its name during the term of the patent. 

[7] The Division specifically considered whether differences arose in: a new group of patients (T 19/86, T 233/96), a new mode of administration (T 51/93), a new dosage (T 56/97, T 230/01) or a new clinical situation (T 384/03, T 1229/03). Differences were found only to relate to the apparatus features.