T 0070/23: Is “immunogenic” a technical feature or just a label?

In T 0070/23, the Board of Appeal (the Board) addressed the patentability of a composition described to be “immunogenic”, and this deceptively straightforward adjective came under discussion. The decision pivots on whether the presence of “immunogenic” in claim 1 imports a functional requirement or merely labels the composition as possessing the potential to induce an immune response. The outcome directly influenced the assessment of inventive step.

Claim language and the role of “immunogenic”

Claim 1 of the opposition-appeal concerned a multivalent composition of saccharide-protein conjugates derived from various Streptococcus agalactiae (GBS) serotypes, with one notable specification: the serotype V component had a N-acetylneuraminic acid (NeuNAc) content of >90%. Central to the debate was the use of the term “immunogenic” to characterise the composition. The Respondent (P) argued that “immunogenic” implies a therapeutic effect — namely, that each component induces a protective immune response. The Appellant (O), in contrast, contended that the term merely describes a property in a broad sense, without requiring vaccine-level efficacy.

The Board’s claim construction

The Board sided with the Appellant on this point. Following the principles in T932/99 and T1018/02, the Board stated that 

Despite paragraph [0045] of the patent hinting at therapeutic intent, the Board held that the claim was not purpose-limited under Art. 54(5) EPC, and efficacy was not a functional feature.

This had immediate consequences: the Board refused to adopt the Patentee’s proposed formulation of the technical problem (“providing an improved vaccine”) and instead redefined it as the “provision of a further immunogenic GBS composition”. In doing so, the Board effectively narrowed the scope of assessable inventive merit to the mere provision of an alternative composition with similar properties — not better ones.

Inventive step and the impact of claim language

The two main distinguishing features over the prior art (D1; WO 2012/035519) were identified to be:

1. The inclusion of a serotype II conjugate
2. The NeuNAc content of the serotype V saccharide being >90% (i.e., not desialylated)

The Board found both features to be directly suggested by D1. The inclusion of serotype II was explicitly disclosed, and the use of native (fully sialylated) serotype V saccharides was presented as one of two equal alternatives. Referring to T674/08 and T892/08, the Board concluded that arbitrary selections between equally obvious options do not confer inventiveness.

P attempted to rely on data from the patent in suit to show that NeuNAc levels had a marked effect on immunogenicity. However, this line of argument failed. First, as the Board reminded, the claim was not limited to compositions with demonstrated therapeutic effect — thus such a feature could not retroactively elevate the claim’s technical contribution. Second, the data was not aligned with the full breadth of the claim.

T0070/23 reminds us to be aware of word choices in claim drafting, particularly when using functional terminology like “immunogenic”. In this case, the absence of structural or functional qualifiers meant that the term “immunogenic” failed to distinguish the claimed subject-matter from the prior art, and the Board concluded there was no inventive step and the patent was revoked.

Summary written by the NLO EPO Case Law Team