Second or subsequent medical uses represent a salient category of patent claims in therapeutics, safeguarding the adoption of a known substance or compound for a new and specific medical purpose.
Besides benefitting more patients, repurposing existing drugs to treat different diseases provides further options for clinicians and can prove to be very successful for healthcare companies.
Reach out to medical patent experts
Some well-known examples of second medical uses include:
- Aspirin: Originally used as a painkiller (analgesic) and anti-inflammatory, aspirin was later found to be effective in reducing the risk of heart attacks and strokes.
- Thalidomide: Initially used as a sedative and to treat morning sickness, thalidomide was later employed to treat leprosy and multiple myeloma.
- Minoxidil: Originally developed to treat high blood pressure, minoxidil was later discovered to promote hair growth and is now widely used as a treatment for pattern baldness.
- Sildenafil: Initially developed to treat hypertension and angina, sildenafil was later found to be effective in treating erectile dysfunction.
As mentioned, such second or subsequent medical uses are recognized as being patentable in many countries, albeit with some jurisdictional peculiarities and several issues that still need to be addressed. However, to be satisfactory, any resolution needs to consider that the patentability of second medical uses must also align with the development of biotechnologies – research fields enabling the identification of mechanisms of action, biomarkers and new therapeutic modalities.
Even though they hold great utility for pharmaceutical innovation, second medical use claims are the frequent target of criticism for their tendency to appear in patent thickets of "low-quality or even duplicative" grants.
In light of their technical complexity, economic potential and legal nuance, patents relating to second and subsequent medical uses have been central to several high-profile Intellectual Property (IP) disputes in Europe.
Legal provisions in Europe
Within the legal framework provided by the European Patent Convention (EPC) and the case law of the European Patent Office (EPO) Technical Boards of Appeal, it is now clear that a new therapeutic application is not to be confined to treating an ailment other than that originally targeted in the state of the art. Admissible claims may relate to a drug's dosage or method of administration, the changing of a drug's functioning at a physiological or cellular level or even validating the use of a therapy for a new class of patients with specific characteristics.
The legal basis in the EPC is provided by Article 54(5), which grants protection to a product (i.e., a substance or composition) whose scope is limited to the express function or purpose claimed. Such second medical use inventions must demonstrate their departure from the first-use invention; hence, they need to claim a specific utilization within a method referred to in Article 53(c) EPC, i.e., surgery, therapy or diagnosis practiced on the human or animal body.
EPO developments
According to Section 6.1 of the EPO Examination Guidelines, product claims for further medical uses may be patentable provided they fulfill all patentability requirements, with particular emphasis on inventive step.
In contrast to "normal" product claims, where the invention must contain at least one technical feature distinguishing it from the state of the art to make for a positive novelty assessment, in cases of second and subsequent medical uses, the product as defined in the claim is per se identical to a former one. While "any specific use" contained within Article 54(5) does not introduce an additional hurdle to the novelty assessment, it is important to remember that the inventive step requisite will further demand that the claimed use not be simply lexically different from the prior art, but also reflect a different (and inventive) technical teaching.
Strict examination criteria at the EPO seek to screen out claims reproducing the state of the art in other terms. In turn, this diligence helps remove impediments to the marketing of generic alternatives and biosimilars.
This topic was most recently addressed by the EPO Enlarged Board of Appeal in its decision G 0002/21 (Reliance on a purported technical effect for inventive step (plausibility)), published in March 2023. The action concerned the permissibility of post-filed evidence to support a technical effect relied upon for acknowledgment of inventive step.
While this case did not concern an application for a second medical use patent, it did review the law on "plausibility" regarding second medical use claims. As the Board stated: "For such claims, the issue of reliance on post-published evidence for a purported technical effect arises in particular in the context of sufficiency of disclosure."
Plausibility has been at the heart of many recent patent cases, including those relating to second medical uses, both in terms of inventive step (Article 56 EPC) and sufficiency of disclosure (Article 83 EPC). The Board's conclusions in this case were:
I. Evidence submitted by a patent applicant or proprietor to prove a technical effect relied upon for acknowledgement of inventive step of the claimed subject-matter may not be disregarded solely on the ground that such evidence, on which the effect rests, had not been public before the filing date of the patent in suit and was filed after that date.
II. A patent applicant or proprietor may rely upon a technical effect for inventive step if the skilled person, having the common general knowledge in mind, and based on the application as originally filed, would derive said effect as being encompassed by the technical teaching and embodied by the same originally disclosed invention.
It is well established in the case law from the Boards of Appeal of the EPO that a patent application directed to a second medical use must provide adequate evidence to support the claimed therapeutic purpose (see, for example, decision T 0609/02). However, as confirmed in T 0950/13, it is not always necessary for the evidence to be in the form of experimental tests: "[T]he disclosure of experimental results in the application is not always required to establish sufficiency, in particular if the application discloses a plausible technical concept and there are no substantiated doubts that the claimed concept can be put into practice."
Credibly inferring an equivalence of effect to known therapeutics may satisfy disclosure requirements. However, this should be supported empirically wherever possible, even after the application filing date.
In summary, it is clear from EPO case law that, in order for second medical use claims to be considered allowable, it is necessary for the specification as filed to include appropriate evidence, which may take the form of tenable instruction.
Examining further recent decisions dealing with second medical use claims in European Patents provides a more complete picture of many of the finer points.
Under the EPO legal microscope
T 1356/21: This decision pertains to dosage regimens and provides guidance on the novelty and inventive steps of numerical ranges. The Board of Appeal determined that a narrow range can be considered novel if it demonstrates distinct technical effects compared to the closest prior art and that it is "not required that these effects exclusively arise in the claimed range [...] for them to be acknowledged and taken into account."
T 1252/20: This instance clarifies which subject matter is eligible for second medical use under Articles 53(c) and 54(4) or (5) EPC. The question arose because there is no legal basis or criterion for qualifying a material or object as a substance or composition under Article 54(5) EPC despite its implicit requirement to distinguish them from devices. Attributing status as a substance or composition should be undertaken, from the first, on the basis of the claimed material or object as such. Here, the Board of Appeal set out that second medical use may be claimed for substances and / or compositions responsible for a therapeutic effect, irrespective of whether this effect is achieved through chemical properties or mechanical interactions.
In drawing this conclusion, the Board disagreed with the previous approach taken in the case law (see T 2003/08 and T 1758/15) of restricting second medical use claims to products having a chemical (as opposed to physical) mode of action. For the Board of Appeal in T 1252/20, the "substance or composition" category should include any product that may be defined by its chemical composition, regardless of the product's mode of action in the body.
Just as molecular arrangements are trialed by experiment, the expanding body of cases decided by the EPO's Boards of Appeal is refining our knowledge of the interpretation and suitability of second medical use claims.
T 0558/20: The Board of Appeal indicated that the novelty of a second medical use should be assessed as a whole and not be restricted to the direct "medical use" steps of the claimed composition. In the discussed case, claim 1 of the patent concerned using a specific material to treat a degenerative bone condition. The method included surgical steps, such as creating space in the bone to insert the regenerative composition. However, at the priority date, the substance was already marketed for this purpose, meaning the only "characterizing" aspect of the method lay in the surgical steps.
The Board's decision stated that a second medical use claim can be considered novel if it includes surgical steps integral to the method defined, even if the substance or composition and its therapeutic usage are already known. A practical consequence is that second medical use claims may be drafted to include novelty-enhancing surgical steps, creating new opportunities to obtain patents for medical innovations involving known substances or compositions.
T 0468/20: Issues of clarity were the Board of Appeal's main concern in this case. Specifically, the employment of the expression "interfering with" to describe the interaction of autoantibodies was considered intrinsically unclear since it could have meant disturbing, impairing, inhibiting, etc., thus rendering the nature of the effect vague. Additionally, the Board reviewed a second medical use claim and found that it was drafted so as to involve a device rather than a substance or composition, meaning the scope of protection needed to be descriptive rather than restrictive. For this reason, and since the claim category could not be univocally determined, the claim was rejected under Article 84 EPC for being ambiguous and unclear.
Thus, it can be seen that in spite of their compelling draw for innovative pharmaceutical companies, second medical use patents represent a challenging undertaking – a delicate negotiation of scientific and legal technicalities, with the latter sometimes resisting absolute measurement.
The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.
