On 24 April 2025, the 1st Chamber of the Supreme Court handed down the long-awaited ruling on plausibility in the apixaban case. The Judgment is available at the following link of the Judicial Documentation Centre (CENDOJ): STS (Sala 1a) 1714/2025, 24 April.
In this commentary, we briefly analyse the aforementioned ruling and consider whether the Supreme Court really intended to establish a criterion of plausibility that will condition future rulings in Spain. In our opinion, it does not appear that this is necessarily the case based on the content of the ruling.
First of all, we should point out that a Supreme Court ruling does not create case law, but at least two rulings of the High Court in the same sense on the same legal question are necessary (Art. 1.2 Civil Code). To date, the judgment under discussion is the only Supreme Court ruling on the legal issue of plausibility in Spain.
Before analysing the Judgment, we would like to put the reader in the context of the facts of the case.
The action was for invalidity of patent EP 1 427 415 for lack of inventive step (Art. 56 EPC) of all its claims and, additionally, for insufficiency of disclosure of those claims referring to therapeutic uses (Art. 83 EPC). The legal issue raised in the claim concerned the plausibility of the technical effect of the subject matter of the contested claims according to the contents of the patent application WO 03/026652, i.e. the patent application referred to above, interpreted with the common general knowledge of the person skilled in the art (“CGK”).
During the legal proceedings in Spain, the Enlarged Board of Appeal of the European Patent Office (EBA) issued its Decision G 2/21, which, in trying to resolve an alleged tension between the ab initio plausibility and ab initio implausibility approach, proposed an interpretation that avoided this terminology.
The first question before the Supreme Court was whether the plausibility of the technical effect is an aspect that can be analysed when assessing the requirements of validity of inventive step and sufficiency of disclosure, as it is not a legal requirement for the validity of the patent. In this regard, the Judgment states the following: “It is true that this requirement that the intended technical effect be plausible according to the technical teaching of the patent is not strictly speaking a legal requirement for patentability […] But the analysis of this requirement of inventive step implies that the intended technical effect of the invention is derived from its technical teaching”.
It was also discussed whether the plausibility analysis should be carried out according to the content of the patent application or the granted patent.
In this regard, the Supreme Court recalls that although it is not bound by the decisions of the EPO, it follows its interpretation in view of its authority and the conviction of its reasoning: “Although we are not bound by the decisions of the Enlarged Board, like so many other national courts, we follow its opinion in view of its authority on the matter and the conviction of its reasoning”. Therefore, on the aforementioned disputed question, the Supreme Court, in application of EBA Decision G 2/21, concludes as follows: “The assessment of inventive step must be made at the effective date of the patent and on the basis of the information contained in the application, together with the common general knowledge that would then be available to the skilled person”.
The judgment also states that: “the examination of the plausibility of the claimed technical effect must be limited to apixaban, without prejudice to the fact that it is carried out on the basis of the disclosure contained in the patent application”. In our opinion, this does not mean accepting a hindsight analysis of the application, but simply that the plausibility analysis does not apply to all the compounds claimed in the patent application (it should be remembered that in the case under consideration there were millions of them) but to the compound claimed of the granted patent, notwithstanding that this assessment of the claimed compound hast to be done within the context of all the information disclosed in the application as originally filed.
From this point onwards, the Judgment considers the plausibility test to be applied to the case and in doing so relies on the interpretation given by Decision T 116/18 of the Technical Board of Appeal of the EPO (TBA) on G 2/21, considering that it advocates a test of ab initio implausibility: “This decision G 2/21 has been interpreted by the Board of Appeal which had referred the questions for a preliminary ruling, in Decision T 116/18, that the examination of the requirement that the effect must be capable of deriving from the same invention as the one originally disclosed, translates it into the following question: would the skilled person, having the common general knowledge at the filing date in mind, and based on the application as filed, have legitimate reason to doubt that the technical teaching at issue, i.e. the purported technical effect together with the claimed subject- matter, is an embodiment of the originally disclosed invention, i.e. the broadest technical teaching of the application as filed?”. So […] it is understood that Decision G 2/21 is better aligned with implausibility ab initio (based on the information contained in the patent application or common general knowledge, the person skilled in the art at the filing date of the patent application would have seen no reason to consider the effect implausible)”.
It should be noted that Decision T 116/18 is not the only one to have ruled on the meaning to be given to G 2/21, as other Decisions, such as T 314/20, have ruled otherwise.
However, the latter TBA decision, dissenting from T 116/18, and other decisions which were not on the proceedings were not considered by the Supreme Court.
Finally, as regards the requirement of sufficiency of disclosure, the aforementioned judgment considers that the test of point 77 of G 2/21 would not be applicable to first medical use claims, but to second medical use claims, not because this was mentioned in point 77, but in accordance with the interpretation of G 2/21 given by another TBA decision, T 2037/22 in its point 3.3.
In any case, and in accordance with the words used by the Supreme Court, we understand that the legal question of plausibility is not closed in Spain but will depend on the future interpretation of G 2/21 by the Boards of Appeal of the EPO. Perhaps it would have been desirable for the EBA to have established a less abstract criterion (point 95), which would have facilitated its interpretation by the national courts.