EPO Applies Doctrine of Plausibility to Small Molecule Pharmaceuticals – T 488/16

In Decision T 488/16, the Boards of Appeal of the European Patent Office have revoked EP1169038, which protected the blockbuster protein tyrosine kinase (PTK) inhibitor dasatinib (Sprycel®). The only request on file - a single claim directed to dasatinibper seor a salt thereof - was found to lack inventive step in view of the absence of evidence in the application as filed (and the common general knowledge) which rendered the activity of dasatinib in inhibiting PTK "plausible". A general statement in the application as filed that "Compounds described in the following Examples have been tested in one or more of these assays, and have shown activity" was not by itself considered enough to render it credible to the skilled person that the described compounds were PTK inhibitors. In the absence of a plausible disclosure of activity against PTK in the specification as filed, the objective technical problem was defined by the Board of Appeal as merely "the provision of a further chemical compound". The extensive clinical data which became available after the filing date of the patent evidencing biological activity was not taken into account when determining inventive step.

The Boards of Appeal of the European Patent Office have for many years imposed a requirement that claims for large molecules (e.g. proteins) must be supported by a plausible disclosure of biological activity in the application as filed (see for example T 1329/04). A similar requirement for a plausible disclosure of activity in the original specification has also been required to support medical use claims (see for example T 609/02). However, this Decision indicates that the Boards are willing to apply the same strict standards when assessing claims for small molecule drugs per se.