9.9. Chemical inventions
9.9.5 Predictable improvements resulting from amorphous forms as compared to crystalline forms
In T 777/08 (OJ 2011, 633) the claims in question related to a particular polymorph (form IV) of crystalline atorvastatin hydrate. The board found that the skilled person in the field of pharmaceutical drug development would have been aware of the fact that instances of polymorphism were commonplace in molecules of interest to the pharmaceutical industry, and would have known it to be advisable to screen for polymorphs early on in the drug development process. Moreover, he would be familiar with routine methods of screening. Consequently, in the absence of any technical prejudice and in the absence of any unexpected property, the mere provision of a crystalline form of a known pharmaceutically active compound could not be regarded as involving an inventive step (see also T 41/17, T 1831/18). Further, when starting from the amorphous form of a pharmaceutically active compound as closest prior art, the skilled person would have a clear expectation that a crystalline form thereof would provide a solution to the problem of providing a product having improved filterability and drying characteristics. The arbitrary selection of a specific polymorph from a group of equally suitable candidates cannot be viewed as involving an inventive step.
In T 478/17 the board distinguished the case in hand from T 777/08 and T 41/07. The case in hand was not about the selection of any crystalline form but about the selection of one specific salt, namely eliglustat hemitartrate, in which at least 70% by weight of the salt was crystalline. The selection of this specific salt was not arbitrary. Rather, this salt had unexpected properties, namely an improved (reduced) hygroscopicity and an improved chemical stability. The board could not see any "one-way street situation" in view of D1, as claimed by the appellant. The skilled person starting from D1 would have had various choices in terms of stoichiometry and degree of crystallinity. It concluded that, having regard to the cited prior art, it would not have been obvious to the skilled person to isolate eliglustat hemitartrate in which at least 70% by weight of the salt was crystalline and arrive at the compound as defined in claim 19 of the main request.
In T 1684/16 the board distinguished the case in hand from T 777/08, in the light of which the appellant submitted that the solution in the case in hand was obvious since screening of polymorphs was a routine task as demonstrated in the prior art. Unlike T 777/08 the case in hand was not about the selection of any crystalline form but about the selection of one specific crystalline form (Form I of bosutinib monohydrate). The board found that the selection of this specific crystalline form was not arbitrary, but rather this form had unexpected properties, namely an improved stability when compared with the other crystalline forms in D1, D2 and D3. The fact that the skilled person was taught in the prior art to investigate polymorphs in order to isolate the crystalline form having the most desirable properties was in itself not necessarily sufficient to consider a specific polymorphic form having a certain desired property obvious (see also T 1326/18).
- 2023 compilation “Abstracts of decisions”