In 2008, Teva challenged the patent application for the dehydrophosphate salt (DHP) of sitagliptin. The primary reference was the “basic patent” of sitagliptin, which detailed and claimed several molecules, including sitagliptin itself. This patent listed around 20 salts, with a smaller list of preferred salts, one of which was phosphate salt.
Teva contended that the invention was neither novel nor inventive, given the basic patent. They argued that the salt was inherently revealed in the basic patent, which disclosed the molecule (sitagliptin) and described phosphate salt as preferred. Therefore, a professional following the instructions in the prior art would inevitably produce the invention – sitagliptin dehydrophosphate. Both claims were accepted by the Registrar deputy.
It was determined that since the screening and preparation of crystals is routine in drug development, and the basic patent had already revealed the molecule and the salt, then the difference between the prior art and the invention is the product of a routine procedure that lacks an inventive spark.
Merck appealed this decision to the district court (as well as the ruling related to novelty). Merck’s main argument was that the salt selection process involved examining a large number of salts and the DHP salt was the only suitable salt. Additionally, this salt has unexpected benefits in addition to the recognized benefits of salts, so there is an inventive step.
In this regard, the District Court decided that if the previous publication only mentions the components of the salt, it is necessary to examine the salting process under the circumstances and see if there were difficulties or not. If an inventive spark is required to carry out the salting and also how many salts are obtained, according to the District, if more than one salt can be obtained, this could indicate inventive step.
Another key assertion, is that if there were no difficulties in carrying out the salting, then the mere benefits of the salt are not enough to demonstrate inventive step.
The District Court sent the case back to the ILPO to reconsider the decision regarding inventive step, in light of the guidelines in the ruling.
On June 4, 2023, the Patent Office issued a second decision, determining that the patent application lacked inventive step.
In terms of the requirement for difficulties in the salting process, the Deputy Registrar stated that the applicant did not provide evidence of any difficulties in the preparation of the salt, and therefore, there was no difficulty in preparing the salt.
In relation to the number of salts that can be obtained and the correlation between the number of possible salts and inventive step, it was determined that there is no dispute between the parties that it is easier to obtain the salt claimed in the patent application. Furthermore, it was demonstrated that in practice, Merck performed salting under acceptable conditions in the development process and did not receive salts other than dehydrophosphate salt.
An intriguing (and in my opinion, accurate) statement by the Deputy Registrar, which I believe is also a critique of the district court, is: “Why should I care that you can get more phosphate salts of sitagliptin, which are more difficult to make, when I am examining the inventive step of the salt that is easy to make?” If I were to examine the inventive step of salts that are difficult to make, then the question would be relevant, but that is not the case here.