Patentability Of Chemical Inventions In Europe And Considerations For Drafting ' Purity, Enantiomers And Polymorphs

• Published date: 07 July 2022
• Law Firm: Haseltine Lake Kempner LLP
• Author: Ms Robyn Hardisty

There are unique considerations regarding the patentability of certain chemical inventions. In this article, we look at the case law regarding claims that are distinguished from the prior art solely by their chemical purity, their enantiomeric form, and their polymorph structure.

Chemical Purity

Chemical Purity generally refers to a measurement of the amount of impurities found in a chemical sample. A sample with a purity of 100% would mean the sample contains only one molecule or compound, the sample containing no impurities or side-products.

In both Europe and the UK, it was previously held that any document disclosing a method of making a low molecular weight chemical compound anticipated the production of this molecule in all grades of purity unless evidence was provided to the contrary (see T 990/96). Because methods of purifying such compounds are well-known, it was considered that all purities were considered implicitly disclosed. In order to establish novelty, the burden of proof was therefore on the applicant to demonstrate that conventional methods of obtaining a claimed level of purity of compound had failed.

However, a more recent case in Europe, T 1085/13, departed from this view. In this case, it was reasoned that a claimed purity is only disclosed implicitly if the method of preparing the compound described in the prior art inevitably results in the level of purity as claimed. If a different purification method was used or a further purification is required, the claim should be considered novel over the prior art.

However, in order to be patentable, the claim should also be held to involve an inventive step. To assess this, it is considered whether the skilled person could arrive at a compound having the claimed higher purity using conventional techniques in the art, such as recrystallisation, distillation and chromatography.

With regards to the facts of the particular case in T 1085/13, the claimed compound having a purity...