How the European Patent Office Treats Added Subject Matter: Disclaimers

In a decision dated 31 August 2023, the European Patent Office's Board of Appeal reviewed an appeal from Regeneron Pharmaceuticals Inc. The company was appealing against the revocation of its patent by the Opposition Division. The patent in question is a second-generation divisional patent of a previously filed European patent application titled 'A method of producing an antibody comprising a human variable region and a rodent constant region'.

The Opposition Division had rejected Regeneron's Main Request and several Auxiliary Requests (2 to 11, 13, and 14) due to added subject matter, as per Article 123(2) EPC (European Patent Convention) - 'the European patent application…may not be amended in such a way that it contains subject-matter which extends beyond the content of the application as filed'. Auxiliary Request 12 was refused for lacking clarity under Article 84 EPC.

In response, Regeneron submitted a Main Request and 29 Auxiliary Requests. The Main Request and Auxiliary Requests 1, 2, and 3 had already been considered before the Opposition Division.

Claim 1 of the Main Request reads: 'A method of producing an antibody comprising a human variable region and a rodent constant region, comprising exposing to antigenic stimulation a rodent comprising a hybrid immunoglobulin heavy chain locus that produces said antibody, wherein said hybrid locus comprises human V, D and J gene segments operably linked to rodent heavy chain constant regions, and wherein said rodent does not produce fully human antibodies.'

Claim 1 of all the Requests (Main and 29 Auxiliary) includes the disclaimer 'wherein said rodent/mouse or rat/mouse does not produce fully human antibodies'.

The Board of Appeal found that the disclaimer in question did not disclaim any subject matter that was actually described as part of the invention in the grandparent application. Therefore, they concluded that this disclaimer does not fall under the category of disclaimers described in the European Patent Office's decision G 2/10(1).

It was further undisputed that the disclaimer is not explicitly disclosed in the grandparent application as filed. The Board determined that since the disclaimer was not clearly disclosed and was only vaguely implied rather than explicitly stated, it qualifies as an undisclosed disclaimer. According to the Enlarged Board of Appeal decisions G 1/03(2), G 2/03, and G 1/16 (confirming G 1/03 and G 2/03), this type of disclaimer is not permissible as it does not fit into any of the established categories. Therefore, the disclaimer is considered added matter and is not allowable.

The Board also examined whether the disclaimer could be derived from the grandparent application using the 'gold' standard for making amendments to patent applications - 'what a skilled person would derive directly and unambiguously, using common general knowledge, and seen objectively and relative to the date of filing, from the whole of [the] documents [of the application] as filed' (Enlarged Board of Appeal decisions G 2/10 (point 4.3) and G 1/16 (point 17)).

Claim 1 of Auxiliary Request 18 was considered because it is the most restricted claim for which Regeneron provided specific arguments. This claim reads: 'A method of producing an antibody comprising a human variable region and a mouse constant region, comprising exposing to antigenic stimulation a mouse comprising a hybrid immunoglobulin heavy chain locus that produces said antibody, wherein said hybrid locus comprises human V, D and J gene segments operably linked to endogenous mouse heavy chain constant regions at the mouse chromosomal immunoglobulin heavy chain locus, and wherein said mouse does not produce fully human antibodies.'

Regeneron considered that the basis for this claim could be found in claim 30 and the description on pages 42-43 of the grandparent application as filed.

Claim 30 of the grandparent application, as filed, reads: 'A transgenic mouse having a genome comprising human heavy and/or light chain variable region loci operably linked to endogenous mouse constant region loci such that the mouse produces a serum containing an antibody comprising a human variable region and a mouse constant region in response to antigenic stimulation.'

The Board noted that both Claim 1 of Auxiliary Request 18 and Claim 30 of the grandparent application describe a mouse with a human variable region connected to its natural mouse constant region. However, Claim 30 from the grandparent application does not specify that "said mouse does not produce fully human antibodies." On the other hand, Claim 1 of Auxiliary Request 18 reads, 'a transgenic mouse having a genome comprising human heavy and/or light chain variable region loci…'. This means the claim covers mice with additional genetic modifications, potentially allowing these mice to produce fully human antibodies.

Regeneron based their disclaimer on Example 3 from the grandparent application. They argued that this example "implicitly" indicated that the mice generated did not produce fully human antibodies.

However, on page 42 of the grandparent application, while prior art regarding fully human antibodies is mentioned, there is no indication that these antibodies need to be completely avoided or that they are incompatible with the claimed method. Instead, the text suggests that the prior art method "has not resulted in optimal antibodies." Therefore, this section does not support the basis for the disclaimer.

Example 3 relates to a specific method and the resulting mouse having certain genetic modifications, most of which technical features are not in Claim 1 of Auxiliary Request 18.

Additionally, since Claim 30 of the grandparent application describes a mouse in a much broader manner than the specific mouse in Example 3, the Board believed that a skilled person would not see a reason to apply any implicit limitations from Example 3 to the more general mouse described in Claim 30. Therefore, they would not arrive at the subject matter of Claim 1 of Auxiliary Request 18 based on this.

Therefore, the Board concluded that Claim 1 of Auxiliary Request 18 contains added subject matter. This finding was then extended to all the other Requests, leading to the dismissal of the Appeal.

This case highlights the EPO's strict stance on maintaining the integrity of patent applications and ensuring that amendments do not introduce new subject matter beyond what was originally disclosed. If you have any questions, please email us at mail@stratagemipm.co.uk.

(1) G 2/10 Order point 1a reads 'an amendment to a claim by the introduction of a disclaimer disclaiming from it subject-matter disclosed in the application as filed infringes Article 123(2) EPC if the subject-matter remaining in the claim after the introduction of the disclaimer is not, be it explicitly or implicitly, directly and unambiguously disclosed to the skilled person using common general knowledge, in the application as filed'.

(2) G 1/03 and G 2/03 Order point 2.1 reads: 'a disclaimer may be allowable in order to:

- restore novelty by delimiting a claim against state of the art under Article 54(3) [prior filed European patent applications published subsequent to the filing date of the application under examination] and (4) [methods for medical treatment] EPC;

- restore novelty by delimiting a claim against an accidental anticipation under Article 54(2) EPC [prior published art]; an anticipation is accidental if it is so unrelated to and remote from the claimed invention that the person skilled in the art would never have taken it into consideration when making the invention; and

- disclaim subject-matter which, under Articles 52 to 57 EPC, is excluded from patentability for non-technical reasons.'