Netherlands: Supreme Court rules on role of description in claim interpretation

August 29 2018

Resolution Chemicals v AstraZeneca B.V. and Shionogi (Supreme Court of The Netherlands, The Hague, June 8 2018) deals with the extent of protection that is conferred by patent EP0521471 (EP 471), for rosuvastatin, a new cholesterol inhibitor.

Claim 1 of EP 471 does not claim the active ingredient of rosuvastatin (i.e. the rosuvastatin anion), but "the compound [rosuvastatin, described using its molecular formula] acid or a non-toxic pharmaceutically acceptable salt thereof''.

Resolution took the position that the feature "or a non-toxic pharmaceutically acceptable salt thereof" in claim 1 must be interpreted to only comprise the salts mentioned in paragraph [0007] of the patent, stating that "the term "a non-toxic pharmaceutically acceptable salt" refers to a salt in which the cation is an alkali metal ion, an alkaline earth metal ion, or an ammonium ion". Hence, claim 1 must be interpreted more strictly than the literal claim wording gives rise to, and rosuvastatin zinc is outside the scope.

AstraZeneca argued that the average skilled person, taking into account his general professional knowledge, would take paragraph [0007] to merely provide a non-exhaustive list of suitable salts, and that "a non-toxic pharmaceutically acceptable salt" should be understood to include the zinc salt.

The district court concluded that the skilled person would presume that the list of salts in paragraph [0007] was a conscious choice by the patentee and thus construe this paragraph as a limiting definition. It therefore ruled that the zinc salt was not within the scope of EP 471.

The Court of Appeal reversed this decision, and ruled that the average skilled person would have understood that the inventive idea does not reside in identifying suitable salt forms, but in providing a new cholesterol inhibitor having a better biological activity than existing compounds. Accordingly, he would not interpret the patent to "waive'' protection for salts of rosuvastatin other than those mentioned in [0007].

The Supreme Court rejected Resolution's complaint that the Court of Appeal had given more weight to the "essence of the invention'' than what is written in the description and affirmed the Court of Appeal's decision, indicating that it explained the patent claims in light of the common general knowledge of the average skilled person. In addition to this, it also addressed the contribution of rosuvastatin to the art, the role of salt forms in a pharmaceutical rosuvastatin composition, and the fact that EP 471 as a compound patent conferred absolute product protection. It further indicated that, when finding a fair balance according to the Protocol to Article 69 of the European Patent Convention, weight must be given to the skilled person's opinion on whether there are valid reasons for a limitation of the scope of protection. This decision indicates that the waiver doctrine as formulated in the Van Bentum v Kool decision of 2002 no longer has an independent significance as a separate test.