Decision T 488/16 of the Boards of Appeal of the EPO has been published setting out the reasoning for the revocation of European patent number EP1169038 protecting the anti-cancer drug dasatinib (Sprycel®). The Decision represents an interesting development of the doctrine of “plausibility”, particularly in relation to small molecule pharmaceuticals.

The patent owner had sought to defend the patent on the basis of just one claim directed to the single compound dasatinib. The novelty of this compound was not in dispute, and the case hinged on the extent to which the patent owner was entitled to rely on the activity of the compound (as a PTK inhibitor) as a technical effect when seeking to establish an inventive step.

According to established EPO jurisprudence (see, e.g. T 939/92 and T 1329/04), a technical effect can only be relied upon for inventive step to the extent that it was “at least made plausible” in the application as filed. Post-published evidence cannot be used to demonstrate a technical effect that was not made at least plausible by 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).

Here, the application as filed disclosed a broad group of compounds generally and 580 specific compounds including dasatinib. It also discussed PTK inhibition and associated disease targets, and described assays by which PTK inhibitory activity can be tested. It also stated 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 mere statement that compounds had been found to be active was not considered sufficient 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 none were available.

Since activity had not been “at least made plausible” for dasatinib in the application as filed, the patent owner could not rely on post-published activity data. As such, it could not rely on the PTK inhibitory activity of dasatinib for inventive step. The problem to be solved was therefore the mere provision of a further chemical compound, which is not considered to be inventive (see, e.g., T 939/92). The patent was therefore revoked.

A number of important facts influenced the Board’s conclusion, particularly the breadth of the application as filed, lack of structural commonality between the compounds disclosed, missing details in the PTK inhibition assays, and lack of relevant common general knowledge at the filing date. Nevertheless, the complete absence of any verifiable data was decisive to the outcome.

This Decision appears to raise the plausibility threshold somewhat (at least for small molecule pharmaceuticals) and underlines the importance of including verifiable facts (e.g. actual data) at the time of filing. It also seems that attacking plausibility will become a more popular approach in opposition proceedings.