So-called second medical use claims are a type of patent claim in the field of medicine. These claims are typically used to protect the use of a known substance or compound for a new and specific medical purpose.
For example, if Drug X is known for treating hypertension, a second medical use claim might cover the use of Drug X for treating migraine. The novelty lies in the discovery of a new therapeutic application for the existing compound. As well as treating a new disease or condition, a new therapeutic application may involve treating a specific target population, or achieving a therapeutic effect in a novel way.
These claims are valuable to the pharmaceutical industry as they allow companies to extend the patent protection of their drugs by identifying new therapeutic uses for existing compounds. They can thus incentivise further research and development in the medical field.
Last year, the Enlarged Board of Appeal (EBA) of the European Patent Office (EPO) issued decision G2/21, concerning the permitted use of post-filed evidence to support the patentability of a claimed invention. Others, including some of my colleagues (see here, and here), have commented on this decision and I do not wish to go over old ground here. However, it is important to point out that the binding part of the decision only refers to the submission of post-filed evidence in the support of proving a technical effect relied upon for acknowledgement of inventive step. Does this leave open the question of post-filed evidence in support of sufficiency?
Interestingly, the EBA in a preliminary communication (dated 13 October 2022) indicated that “the referral arose in the context of inventive step” and so did not consider “it appropriate to extend the clear scope of the referral beyond what the referring board identified as decisive for its decision”. Thus, the EBA chose not to consider the effect of post-filed evidence in support of sufficiency (Article 83 EPC). Nevertheless, in its decision, the EBA expressed an intermediate conclusion concerning sufficiency of disclosure, as “the Enlarged Board accepts the appropriateness of a comparative analysis and comparative considerations”, between inventive step and sufficiency requirements.
Whilst it is common for the EBA only to rule on the specific point of law that has been referred to it, it would seem that the EBA wanted to lay out its views in relation to sufficiency and the use of post-filed evidence, perhaps to mitigate against possible further referrals being made in the future.
With respect to second medial use claims, the EBA wrote at point 74 of the decision:
“Indeed, a technical effect, which in the case of for example a second medical use claim is usually a therapeutic effect, is a feature of the claim, so that the issue of whether it has been shown that this effect is achieved is a question of sufficiency of disclosure under Article 83 EPC.
Hence, because the subject-matter of second medical use claims is commonly limited to a known therapeutic agent for use in a new therapeutic application, it is necessary that the patent at the date of its filing renders it credible that the known therapeutic agent, i.e. the product, is suitable for the claimed therapeutic application”.
The EBA reviewed and considered some of the relevant case law in respect of therapeutic applications and sufficiency of disclosure and concluded at point 77:
“The reasoned findings of the boards of appeal in the decisions referred to above make clear that the scope of reliance on post published evidence is much narrower under sufficiency of disclosure (Article 83 EPC) compared to the situation under inventive step (Article 56 EPC). In order to meet the requirement that the disclosure of the invention be sufficiently clear and complete for it to be carried out by the person skilled in the art, the proof of a claimed therapeutic effect has to be provided in the application as filed, in particular if, in the absence of experimental data in the application as filed, it would not be credible to the skilled person that the therapeutic effect is achieved. A lack in this respect cannot be remedied by post-published evidence”.
Thus, the EBA gave a clear indication, even though the binding part of the decision was formally restricted to the consideration of inventive step, that it did not consider it appropriate to diverge from the existing case law in respect of the use of post-filed evidence in the support of sufficiency arguments. 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 evidence to support the claimed therapeutic application. Seminal decision T609/02 summarises the position nicely:
“It is required that the patent provides some information in the form of, for example, experimental tests, to the avail that the claimed compound has a direct effect on a metabolic mechanism specifically involved in the disease, this mechanism being either known from the prior art or demonstrated in the patent per se. [...] Once this evidence is available from the patent application, then post-published (so-called) expert evidence (if any) may be taken into account, but only to back-up the findings in the patent application in relation to the use of the ingredient as a pharmaceutical, and not to establish sufficiency of disclosure on their own.".
However, it is not always necessary that the evidence be in the form of experimental tests, as confirmed in T950/13 (when referring to T788/06):
“the 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”.
Nevertheless, it seems clear that, unless a second medical use patent application as filed includes evidence to support the claimed second medical use, the patent application may be deemed insufficient and be refused. Moreover, absence of this cannot be remedied by use of post-filed evidence.
However, care must be exercised when drafting second medical use patent applications, to ensure the evidence presented in the specification will meet sufficiency requirements. This is elaborated in T1045/13, where the Board found that:
“The application as filed does not provide any indication of the principle underlying the relationship between the activity of the pharmaceutically active agent, i.e. the NGF, and the therapeutic effect, i.e. the alleviation of the symptoms of the psychological conditions claimed. The description does not provide any information on the mechanism of action of NGF. No background references are cited that link NGF to the therapeutic effects to be obtained, and no in vitro assays are provided to illustrate any such effect. In the complete absence of such information, the experimental evidence on file is of decisive importance”
and:
“To sum up, the appellant has chosen to rely solely on experimental evidence in support of the therapeutic treatment as claimed in claim 1. The experimental evidence on file fails however to provide evidence for the effects claimed. The examples do not cover the whole scope of the claim and do not provide evidence of therapeutic efficacy that meets scientific standards (statistically significant number of patients, control group). Effective treatment of the medical conditions under consideration has thus not been shown”.
The Board further confirmed that failure to meet sufficiency requirement comes with a heavy price, as this cannot be rectified by post-filed evidence, where it said:
It is established case law that once evidence is available from the patent application as filed, then post-published evidence may be taken into account, but only to back up the findings in the patent application. Post-published evidence cannot establish sufficiency of disclosure on its own.
In summary, it seems clear from the EPO case law that, in order for second medical use claims to be considered allowable, it is necessary for the application to include appropriate evidence in the specification as filed. Moreover, failure to include appropriate evidence to establish sufficiency, at the time of filing, cannot be rectified by the use of post-filed evidence. Although the binding portion of G2/21 is directed to matters concerning inventive step, it nevertheless appears that the decision provides additional weight to support the established case law in respect of patent applications and claims directed to second medical uses meeting the requirements of sufficiency.
