Court confirms that equivalents doctrine applies to ‘analogy method’ patents


The Borgarting Court of Appeal has returned a judgment in Pfizer v Sandoz (January 30 2008), holding that Sandoz’s method for the production of generic Sertraline infringed Pfizer’s patent under the doctrine of equivalents.

This patent infringement case involved Sandoz’s generic Sertraline (Hexal). Pfizer’s Norwegian Sertraline patent, which expired in 2000 but benefited from a Supplementary Protection Certificate extension until 2005, was a so-called ‘analogy method’ patent. This type of patent is particular to Norway and other countries where, in the 1990s, product patents could not be obtained for pharmaceuticals. If a compound was found to be novel and to involve an inventive step, protection was afforded by granting a method patent, even if the method as such was neither novel nor inventive. In recent years, a number of analogy method patents have been challenged by generic drug companies in Norway and Finland. At issue was the scope of protection under this type of patent and the extent to which the doctrine of equivalents applies to them.

In the case at hand, the district court construed the claims rather narrowly and found for Sandoz. The Borgarting Court of Appeal quashed the district court’s decision and found for Pfizer. The court awarded sizeable damages of Nkr8 million (approximately £700,000) and all costs to Pfizer.

Under the test of equivalence, the court must examine whether: 

  • the infringing object solves the same problem as the patented invention; 
  • the modifications made were obvious to the average person skilled in the art; and 
  • the infringing object was in the art at the date of the patent application.

Noting that the point in dispute was whether Sandoz’s method for the preparation of Sertraline was obvious to the skilled person, the court compared Sandoz’s process with Pfizer’s patented method. The court noted that Pfizer’s method comprises two known organic reactions, both of which are exemplified in the specification of the patent. The method was referred to as simple but efficient in terms of its yield and the number of steps that it comprises.

Sandoz’s method has the same starting material as Pfizer’s. It follows the same main principles as Pfizer’s method, but there are four steps. The isolation of the final compound is identical and the process is also efficient as regards yield. The court noted that there were both similarities and differences between the two methods. As Sandoz claimed that its method constituted an improved synthesis, the court analysed whether the method provided advantages or technical progress compared to Pfizer’s method.

First, the court held that the obvious disadvantage of Sandoz’s process is that it requires two additional steps, with the risk that by-products may be formed. Moreover, the process requires higher temperatures and a higher amount of chemicals. In order for Sandoz’s process to be considered as a more cost-effective method, and not as an indirect approach devised to circumvent Pfizer’s patent, the disadvantages of the process would have to be more than outweighed by its advantages.

The court also examined the issue of the use of benzyl amine (in Sandoz’s case) instead of methylamine (in Pfizer’s case) for the formation of imine. Sandoz asserted that in the case of analogy method patents, only methods that have been included as examples in the patent specification can be protected. This rule was established by the now repealed patent regulations. The court noted that only one of the examples in Pfizer’s patent dealt with the preparation of Sertraline and that the use of titanium tetrachloride was envisaged in that example. However, the court interpreted the relevant provision of the patent regulations as not preventing the use of a different acid catalyst, as long as the claim did not exclude it. The court also noted that a skilled person knew that titanium tetrachloride could be replaced by other acid catalysts. Titanium tetrachloride also has the function of removing water from the reaction mixture, thereby driving the reaction. Replacing titanium tetrachloride with aseotropic distillation to remove water represented an advantage, but both methods were known and obvious to the skilled person. The court found that the advantage of using a better method to remove water did not outweigh the disadvantages of having additional steps in the synthesis.

In addition, the court found that Sandoz’s introduction of a benzyl group seemed to be an attempt to circumvent Pfizer’s patent. Sandoz introduced a group that was not intended to be part of the final product and subsequently removed it. The court rejected Sandoz’s contention that the use of a benzyl group to increase the cis/trans ratio - and thus the yield - had been substantiated and that the choice of catalyst was the most important and decisive factor for optimising the cis/trans ratio. Accordingly, the court stated that Pfizer’s patent was not limited to the use of a specific catalyst.

Therefore, the court found that the main principles of the two methods were the same, but that Sandoz’s method (which had two extra steps and a more elaborate process in terms of work, chemicals and energy use) had disadvantages. The court held that Sandoz’s method was obvious to the skilled person at the time of filing of Pfizer’s patent application and that Sandoz’s method did not represent an improvement. The court concluded that Sandoz’s process was based on well-known chemical methods and sought to circumvent Pfizer’s patent. Therefore, Sandoz’s method infringed Pfizer’s patent under the doctrine of equivalents.

The court’s decision is in line with Norwegian case law in that it confirms that the doctrine of equivalents also applies to analogy method patents. The court also examined the issue of whether Sandoz’s alternative method had clear advantages over Pfizer’s patented method, thus confirming that technical advantages are relevant, if not decisive.

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