When prosecuting inventions pertaining to chemical subject-matter before the European Patent Office (EPO), it is often helpful to demonstrate that the claimed compounds are improved relative to those in the prior art. The most convincing and successful way of doing so is to provide experimental data directly comparing the claimed compounds to those already known. However, using the EPO's preferred problem-solution approach, it is not uncommon for the closest prior art to have been unknown to the applicant at the time of filing. As such, the application as filed may not contain the necessary comparative data needed to demonstrate an improved and unexpected technical effect over the closest prior art.
In order to prevent applicants from being disadvantaged in such situations, the EPO allows post-published experimental data to be filed in support of an inventive step. In taking this approach, the question nevertheless arose whether post-published evidence may be used to support any technical effect, a stance which could lead to the proliferation of so-called "armchair inventors", or instead only a technical effect already made plausible by the application as filed.
This question was the subject of the March 2023 decision from the EPO's Enlarged Board of Appeal in G 2/21 (Reliance on a purported technical effect for inventive step (plausibility)). In brief, the Enlarged Board found that post-published evidence may be used to prove a technical effect, so long as "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".
The decision of the Enlarged Board has been seen by the European patent community as being generally patentee-friendly, with the test of whether the technical effect is "encompassed by the technical teaching and embodied by the same originally disclosed invention" being considered a relatively low threshold to cross.
In the decision T 1994/22, the Board of Appeal had to consider whether a technical effect relied on by the patentee for inventive step met the criteria established in G 2/21. The decision relates to polymorphs – a contentious and evolving area of the chemical patent space.
Case Background
T 1994/22 is an appeal by Generics UK Ltd. in view of the decision by the Opposition Division to reject their opposition filed against European patent No. 3275871 in the name of Nippon Shinyaku Co., Ltd. Claim 1 of the patent relates to polymorphic Form II of the drug selexipag, an agonist of the prostaglandin receptor PG12 and which is used in treating pulmonary arterial hypertension. The only issue on appeal was whether the claims were inventive.
In Europe, it is possible to patent individual polymorphic forms of chemical compounds, however it can sometimes be difficult to demonstrate that a particular polymorphic form is inventive. In brief, the EPO takes the view that the skilled person is already motivated to find new polymorphic forms of compounds. Therefore, for a polymorph to be found inventive, applicants typically have to demonstrate that the claimed polymorph is associated with unexpected properties. A more detailed discussion of the EPO's approach to the inventiveness of polymorphs can be found here.
For inventive step, the patentee relied on post-published data demonstrating that tablets comprising Form II of selexipag exhibited improved photostability relative to tablets comprising Form III. It was therefore for the Board to decide whether the technical effect of improved photostability was encompassed by the technical teaching and embodied by the same originally disclosed invention as the application as filed.
Applying G 2/21
In arguing for the post-published data to be taken into account, the patentee highlighted passages of the decision T 116/18, this being the referring decision for G 2/21. In T 116/18, the Board specifically noted that a technical effect does not need to be literally disclosed in the application as filed by way of a positive statement for it to be considered encompassed by the same technical teaching. Instead, it may be sufficient for the skilled person to recognize that said effect is necessarily relevant to the claimed subject-matter.
In the present case, the application as filed made no mention whatsoever of photostability. As such, the patentee relied on more general statements, such as that the application sought to provide a novel crystal of selexipag which may be used in a medicament of "high quality for which constant effect can be always shown and of a form which is handled easily industrially". According to the patentee, the skilled person would understand the technical effect of improved photostability as being implied by or at least related to this technical problem. Furthermore, it was argued that the skilled person would have no reason to doubt that Form II of selexipag would exhibit improved photostability, and thus, the technical effect was embodied by the same originally disclosed invention.
Although the Board accepted that a verbatim disclosure of a technical effect was not required in order for it to be relied on for inventive step, they nevertheless agreed with the opponent that the technical effect of improved photostability did not meet the conditions set out in G 2/21 for it to be taken into account for the assessment of inventive step. In particular, the Board found the patentee's arguments to be unconvincing for two distinct reasons.
First, the Board did not consider the general references in the application as filed to high quality and easy industrial handling to encompass the technical effect of photostability, let alone that of improved photostability. According to the Board, if broad statements such as "high quality" were considered to encompass specific technical effects such as improved photostability, the first criterion of Headnote II of G 2/21 (that the technical effect is encompassed by the technical teaching of the application as filed) would be meaningless. The Board then went on to highlight that the data of the application as filed was limited to three different properties of selexipag: particle size, residual solvent content, and the amount of impurities. Since none of these properties were related to photostability, the Board concluded that including this new technical effect would change the nature of the invention, and that therefore photostability could not be considered to be encompassed by the teaching of the application as filed.
Secondly, the Board noted that the parts of the application as filed which the patentee had referred to in support of their arguments regarding the technical teaching of the application did not exclusively refer to Form II of selexipag. Instead, Forms I, II, and III were all referred to in equal terms. As such, the Board determined that there was no teaching in these passages of application as filed that Form II of selexipag was preferred, or that it would exhibit improved photostability relative to the other polymorphic forms.
Before concluding that the technical effect of improved photostability could not be taken into account, the Board briefly discussed the decision T 1989/19, this being cited by the patentee in support of their position. Whilst the Board in this decision felt that the technical effect demonstrated by post-published data was encompassed by the technical teaching of the application as filed, the Board in T 1994/22 found that the facts of the present case were different, and therefore warranted a different outcome. In particular, in T 1989/19, both the data of the application as filed and the post-published data related to the technical effect of storage stability. Moreover, there was no accompanying issue of this effect only being present for a particular polymorphic form.
Inventive Step
Once the Board had excluded the post-published photostability data from being taken into account, discussion of inventive step turned to those effects demonstrated by the data of the application as filed. The closest prior art was a document simply disclosing the compound of selexipag, and thus, the distinguishing feature was agreed by all parties to be the provision of a crystalline form, namely Form II, of selexipag.
As noted above, the application provided data relating to particle size, residual solvent content, and the amount of impurities. The patentee had also provided further experimental data relating to thermodynamic stability. Based on these data, the Board concluded that although Form II exhibited the best stability of the three polymorphic forms, it showed only intermediate levels of industrial processability (based on its particle size), residual solvent content, and impurities. Thus, the Board formulated the objective technical problem as the provision of a form of selexipag which was the best for one property, but only intermediate for the others.
Since it is considered routine in Europe to screen polymorphic forms for those with desirable properties, the Board concluded that finding a polymorphic form which is the best in only a single property of those tested is not unexpected (and may even be considered to be inevitable should enough tests be carried out).
Thus, the Board found the selection of Form II of selexipag to be an arbitrary one from a host of alternatives, and the subject-matter of the claims to therefore lack an inventive step. This decision applied equally to each of the auxiliary requests filed by the patentee.
Parent Case
Interestingly, on the same day, the same Board heard an appeal for the parent European patent No. 2447254 in T 672/21. In this decision, claim 1 of the patent was directed to Form I of selexipag, with the same data (apart from that relating to photostability) being relied on for inventive step. In contrast to the fate of the divisional, it was determined that the data demonstrated that Form I exhibited multiple improved properties such as industrial processability and purity. This balance of beneficial properties (as opposed to merely optimizing a single property) was seen as inventive, and the patent was therefore maintained as granted.
Conclusions
As shown by the decision of the Board in T 1994/22, although G 2/21 allows for a certain degree of flexibility when it comes to submitting post-published data, there must nevertheless be some overlap between the technical teaching of the application as filed and the technical effect demonstrated by said data. In addition, the contrast between this decision and that of its parent patent (T 672/21) reinforces that obtaining patent protection for polymorphs in Europe is highly data dependent, with it being essential to demonstrate not only that the claimed polymorph is associated with some form of improvement, but also that this would be unexpected for the skilled person.
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