Résumé de EPC2000 Art 056 pour la décision T1079/18 du 30.01.2023

In T 1079/18 D2 was found by the board to be the closest prior art and form A was singled out as clearly preferred among the solid forms of febuxostat disclosed therein, in particular because it was the most suitable for the preparation of pharmaceutical formulations. This was the same context as that in which form I was also praised in the patent. The board found that the objective technical problem could be formulated as providing a pharmaceutical composition containing a crystalline form of febuxostat which was non-hygroscopic and had higher solubility. Against the background of the common general knowledge concerning polymorphs outlined in the decision, the board found that the skilled person, faced with the problem of providing a crystalline form of febuxostat that has a higher solubility than form A, would clearly be inclined to check whether form A underwent an endothermic phase transition into a new higher-melting form at higher temperatures. Such a form existed or it did not. It found that that the skilled person would have been in a "try and see" situation. Against the background of the common general knowledge and the objective technical problem, the skilled person would most certainly have thought of using DSC to find new solid forms - if only because DSC measures heat flow and is the method of choice for determining exo- and endothermic processes when heating a sample. The board found that by performing a DSC analysis of form A, the skilled person aiming at higher solubility would have identified form I as being the desired form, i.e. a higher-melting form that results from form A by an endothermic phase transition at higher temperatures. In view of the heat-of-transition rule, they would have expected form I to be an enantiotrope of form A and form I to have a higher solubility than form A at temperatures below the transition temperature (somewhere between approx. 175 and 200 °C), i.e. at ambient temperature. Further, the fact that form I merely retained the non-hygroscopicity of form A could be considered merely as a bonus effect that the skilled person inevitably achieved because they were primarily looking for a crystalline form of febuxostat with higher solubility. The board could not agree with the patent proprietor's argument based on decision T 595/90 that form I was inventive already because no way of making it had been found by the effective date of the patent. In T 595/90, the board held at point 5 of the Reasons that "an otherwise obvious entity, may become nevertheless non-obvious and claimable as such, if there is no known way or applicable (analogy) method in the art to make it and the claimed methods for its preparation are therefore the first to achieve this in an inventive manner". However, the present case was different in that the skilled person would have obtained form I in an obvious manner, i.e. the process carried out until form I was obtained was also not based on an inventive step. It followed that the subject-matter of claim 1 of the main request did not involve an inventive step. The main request was not allowable. The board ordered that the decision under appeal be set aside and the patent be revoked.