Classes, subclasses and post-grant amendments before the EPO

Narrowing a chemical class of compounds to a sub-class or to a specific compound can be a legitimate strategy for defending a patent before the European Patent Office. However, where the claim in question also defines the class in quantitative terms, such amendments may give rise to objections under Article 123(3) EPC. This article analyses situations in which such amendments may nevertheless result in an extension of the scope of protection, with reference to the relevant EPO case law.