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Added matter at the European Patent Office
20 June 2017 by Chris Bond

The European Patent Office (EPO) is strict in only permitting amendments during prosecution of European patent applications which are "clearly and unambiguously" derivable from the application as filed.  Any amendments which are not derivable from the application as filed are found to add matter.  In T 99/13, an EPO Technical Board of Appeal considered whether an amendment to the claims added matter. 

The patent application was directed to protein formulations with reduced viscosity.  The claims of the patent application as originally filed were directed to "a stable liquid formulation comprising a protein… having a kinematic viscosity of about 50cs."

During prosecution, the viscosity feature was amended to "having a kinematic viscosity of 50 mm2/s or less at 25°C".  This amendment was made because specifying viscosity without the temperature at which it is measured is an incomplete definition.  In other words, viscosity changes with temperature and a definition of viscosity without the temperature at which it is measured is unclear. 

The original claims of the patent application (as opposed to the patent as granted) did not specify the temperature at which the claimed viscosity was measured.  Therefore, a number of the ten opponents to the granted patent raised an added matter objection.  The opposition division agreed with the objection and revoked the patent on the grounds of added matter.

On appeal, the patentees argued that the application as originally filed did disclose that the recited viscosity was measured at 25°C. 

The Board of Appeal found that on reading claim 1 as originally filed the viscosity requirement did not make sense unless a temperature was specified.  The Board accepted that the temperature was not literally disclosed in the context of the claimed viscosities.  However, the Board said that from the viewpoint of a skilled person reading the original application the viscosity measurement must be met "at the temperature of use of the claimed formulation" and would look to the description for guidance.  The description stated that the intended use of the claimed formulations was for subcutaneous administration.  A preferred temperature of use was stated as 25°C; a number of examples stated the viscosity measurement was made at 25°C. 

The Board of Appeal found that the temperature of measurement "at 25°C" was directly and unambiguously derivable from the application as filed.  Therefore, the feature was found not to add matter.  The case was remitted back to the Opposition Division to consider other grounds of opposition.

This decision shows that it is sometimes possible to make amendments which are not literally disclosed in the application as originally filed.  However, the EPO test for added matter is still very strict.  Therefore, we recommend including as many fall back positions as possible in an application when it is originally filed.  Furthermore, when technical features are defined by measurable parameters, the parameters should be defined so that they make technical sense.