To assess whether these requirements are met, the EPO Boards of Appeal have been considering several factors, including:

• Is a relationship between the claimed subject-matter and the technical effect known?
• Are there any reasons to doubt the technical effect is achieved by the claimed subject-matter?
• Is the selected embodiment preferred in any way?

This article focuses on factor 1 and the contrasting outcomes in T 1989/19 and T 1847/23. In each of these decisions, the boards considered whether the problem of stability is a common technical problem in the field of pharmaceutical compositions.

T 1989/19: post-filed data was admitted

In T 1989/19, the claim at issue related to a crystalline micronisate characterised by particle size, specific surface area, specific heat of solution, and water content.

The claimed water content was a distinguishing feature from the closest prior art and the patent proprietor referred to post-filed test reports as evidence that this feature led to improved storage stability. The Technical Board of Appeal had to decide whether this technical effect was “encompassed by the technical teaching and embodied by the same originally disclosed invention”, in accordance with G 2/21.

The board held that the application focused on the use of the crystalline micronisates as an inhalation powder and taught that a certain particle size range is required for administration by inhalation. The board further held that it could be inferred from the application that particle size stability is an essential prerequisite for the administration of the crystalline micronisates.

The board stated that it was generally known to the skilled person that particle size stability is of crucial importance for the administration of a medicinal product by inhalation. Several documents were cited to establish that this was common general knowledge and were referred to by the board.

Consequently, the board decided that the technical effect of improved storage stability shown in the post-filed documents did not change the nature of the claimed invention and could be considered for inventive step. Based on the post-filed data, an inventive step was acknowledged.

T 1847/23: post-filed data not admitted

In T 1847/23, the claim at issue related to a pharmaceutical composition comprising maropitant, cyclodextrin, and 7-18 mg/ml benzyl alcohol. The closest prior art differed in that the composition comprised 20 mg/ml benzyl alcohol. The patent proprietor filed a set of post-filed stability tests to demonstrate that this difference was associated with improved storage stability.

On the face of it, the facts appear to be similar to those in T 1989/19. However, in contrast to the earlier decision, the Technical Board of Appeal held that the preparation and/or storage of a drug composition at low temperatures is neither systematic nor widely practiced. It was held that there was no indication in the application or prior art that the compositions comprising the active agent maropitant have to be prepared and/or stored under these conditions. On the contrary, in the prior art the injectable maropitant formulation was to be stored at room temperature.

Consequently, the board held that the behaviour of compositions comprising maropitant under low temperatures could not be considered as a common problem and the post-filed stability tests could not be considered. Nonetheless, the claim was deemed inventive because the lower concentration of benzyl alcohol was deemed non-obvious.

Take-home messages

The headnote of G 2/21 explicitly confirmed that common general knowledge should be considered when determining whether post-filed data should be admitted for the purposes of inventive step. However, the decisions in T 1989/19 and T 1847/23 confirm that boards still have significant leeway to establish whether post-filed data does relate to a common technical problem.

The contrasting decisions in T 1989/19 and T 1847/23 indicate that the boards may not consider “storage stability” in general to be a common technical problem in the context of pharmaceutical compositions. The admittance of post-filed data related to improved storage stability is likely to be decided by boards on a case-by-case basis and dependent on, for example, the claimed active agent.

To maximise the likelihood of post-filed data being admitted, patent proprietors should consider filing review articles or textbook extracts to confirm that the data relates to a common technical problem in the context of the claimed active agent. In T 1989/19, the board explicitly referred to several documents to establish what was common general knowledge. Conversely, in T 1847/23 the prior art contradicted the patent proprietor’s contention that the data related to a common problem in the context of the claimed active agent.

We will continue to monitor for further developments relating to G 2/21 and the admittance of post-filed data for inventive step and report on these in upcoming European biotech patent case law webinars. 

Save the date

Our next European biotech patent case law webinar will run on Tuesday 14 July 2026, presented by Simon O’Brien and Tom Pagdin.