When the Boards of Appeal of the European Patent Office revoked European patent number EP1169038 protecting the anti-cancer drug dasatinib (Sprycel®) back in February 2017, the decision attracted considerable attention within the pharmaceutical industry. After a long wait, the written Decision (T 488/16) setting out the Board’s reasoning has now been published, and represents an interesting development of the doctrine of “plausibility”, particularly in relation to small molecule pharmaceuticals.

In the appeal proceedings, the Patentee sought to defend the patent on the basis of just one claim directed to the single compound dasatinib (or a salt thereof). The novelty of this compound was not in dispute. Furthermore, given that it is now an approved anti-cancer drug, the activity of the compound (which is based on it being a protein tyrosine kinase, or PTK, inhibitor) could not reasonably be disputed either. Instead, the case hinged on the extent to which the Patentee was entitled to rely on this activity as a technical effect when seeking to establish an inventive step.

According to the established jurisprudence of the Boards of Appeal of the European Patent Office (see, for example, T 939/92 and T 1329/04), a technical effect can only be relied upon for inventive step to the extent that the technical effect in question was “at least made plausible” in the application as filed. Furthermore, post-published evidence cannot be used to demonstrate a technical effect that was not made at least plausible by the disclosure in the application as filed (although it can be used to corroborate a technical effect which was at least made plausible by the application as filed).

In the present case, the application as filed was directed to an extremely broad group of compounds defined by general chemical formulae, and also disclosed 580 specific compounds of which dasatinib was one. The application also discussed PTK inhibition and associated disease targets generally, and described assays by which PTK inhibitory activity can be tested. The application also included a statement to the effect that compounds of the examples had been tested in one or more of the assays and had shown activity. However, no actual activity data were presented.

The Board found that the mere statement that compounds had been found to be active was not enough to make it at least plausible that dasatinib would be active. The Board noted that a skilled person’s acceptance of an assertion of activity “must be based on verifiable facts”, and concluded that there were none in the present case (either in the application as filed or in the common general knowledge at the filing date).

In view of its conclusion that activity had not been “at least made plausible” for dasatinib in the application as filed, the Board followed the established jurisprudence of the EPO and did not allow the Patentee to rely on post-published activity data. It was therefore not possible to rely on the PTK inhibitory activity of dasatinib or its associated anti-cancer activity for inventive step. As a consequence, the Board concluded that the problem to be solved was the mere provision of a further chemical compound, which is not considered to represent inventive activity (see, e.g., T 939/92). The patent was therefore revoked for lack of inventive step.

It is clear from the Decision that a number of important facts influenced the Board’s conclusion, particularly the breadth of the application as filed, the lack of structural commonality between the compounds disclosed, the fact that the PTK inhibition assays were considered to be missing important details, and the lack of relevant common general knowledge at the filing date. Nevertheless, the complete absence of any verifiable data with regard to the asserted technical effect was decisive to the outcome of this case (notably, the Board emphasised that it was not the absence of any in vivo or clinical data that was the issue, but rather the absence of any verifiable data).

This Decision appears to raise the plausibility threshold somewhat (at least insofar as small molecule pharmaceuticals are concerned) and underlines the importance of ensuring that any technical effects which a patentee may wish to rely upon are adequately supported by verifiable facts (e.g. actual data) at the time of filing a patent application. It also seems likely that seeking to attack plausibility will become an ever-more popular approach by opponents in opposition proceedings.