Is it possible to get patent protection for the use of functionally defined (known and unknown) effectors of a metabolic enzyme, i.e. a new therapeutic concept, for the treatment of a disease or condition under the German Patent Act, but not under the European Patent Convention?
The invention in question was based on the surprise finding that a reduction in the circulating enzymatic activity of Dipeptidyl Peptidase (DP IV) or of DP IV-like enzyme activity in the blood of mammals results in an improved glucose tolerance. The proof-of-concept was only shown with a single small molecule as an enzyme inhibitor (see EP 0 896 538 B1; DE 196 16 486 C2; cf. US 6,303,661 B1).
The Technical Boards of Appeal of the EPO confirmed the revocation of the European Patent by the Opposition Division in March 2008 on the basis of Art. 83 EPC (lack of enablement) (T 1151/04). The Board determined that a person skilled in the art has to carry out an immeasurable number of experiments using trial and error to find the compounds with the required activity due to the functional definition of the compounds and the lack of guidance in the specification in finding such compounds with a reasonable amount of experiments. Even the limitation to (openly defined) aminoacyl thiazolidides did not help to find suitable compounds without undue burden according to the BoA. The decision of the BoA to confirm the revocation of the European patent is in line with the case law of the BoA. According to Art. 83 EPC an invention must be disclosed sufficiently clear and complete to be carried out by a person skilled in the art. In order to evaluate whether a claimed invention is sufficiently disclosed, it must be considered whether the patent contains sufficient information and guidance enabling the skilled person to carry out the invention throughout its scope and without undue burden. For example, an extensive research program must be regarded as imposing an undue burden (see e.g. T 1227/11 of August 2013).
However, the German Supreme Court reversed the decision of the Federal Patent Court with respect to the German patent on which the above-specified European patent claimed its priority in September 2013 (X ZB 8/12 – Dipeptidyl-Peptidase-Inhibitoren). Contrary to the decision of the BoA, the Supreme Court based its decision more on the question of the contribution to the prior art by the invention, here the new therapeutic concept, and not on the issue of undue burden. The Court clarified that a functional definition of compounds in a use claim is generally possible even if the compounds have to be discovered in the future and even if inventive step is necessary therefor. The only prerequisite is that the suitability of the compounds can be experimentally detected in an easy way. As already mentioned, undue burden for the finding of suitable compounds was not an issue of the Court, in particular because the German patent discloses in one example the general suitability of DP IV inhibitors for lowering blood glucose levels.
A direct consequence of the different decisions of the BoA and the BGH is obviously that claims directed to the use of functionally defined compounds or compositions for a specific purpose, which defines the contribution to the prior art, should (additionally) be pursued before the German Patent and Trademark Office instead of the European Patent Office (only).